Header And Logo
|
#include "postgres.h"#include <limits.h>#include <unistd.h>#include <signal.h>#include "access/slru.h"#include "access/transam.h"#include "access/xact.h"#include "catalog/pg_database.h"#include "commands/async.h"#include "funcapi.h"#include "libpq/libpq.h"#include "libpq/pqformat.h"#include "miscadmin.h"#include "storage/ipc.h"#include "storage/lmgr.h"#include "storage/procsignal.h"#include "storage/sinval.h"#include "tcop/tcopprot.h"#include "utils/builtins.h"#include "utils/memutils.h"#include "utils/ps_status.h"#include "utils/timestamp.h"
Go to the source code of this file.
| #define AsyncCtl (&AsyncCtlData) |
Definition at line 254 of file async.c.
Referenced by asyncQueueAddEntries(), asyncQueueAdvanceTail(), asyncQueueReadAllNotifications(), and AsyncShmemInit().
| #define AsyncQueueEntryEmptySize (offsetof(AsyncQueueEntry, data) + 2) |
Definition at line 172 of file async.c.
Referenced by asyncQueueAdvance(), and asyncQueueNotificationToEntry().
| #define InvalidPid (-1) |
Definition at line 210 of file async.c.
Referenced by asyncQueueAdvanceTail(), asyncQueueFillWarning(), and SignalBackends().
| #define NOTIFY_PAYLOAD_MAX_LENGTH (BLCKSZ - NAMEDATALEN - 128) |
Definition at line 146 of file async.c.
Referenced by Async_Notify(), and asyncQueueNotificationToEntry().
| #define QUEUE_BACKEND_PID | ( | i | ) | (asyncQueueControl->backend[i].pid) |
Definition at line 246 of file async.c.
Referenced by asyncQueueAdvanceTail(), asyncQueueFillWarning(), asyncQueueReadAllNotifications(), asyncQueueUnregister(), AsyncShmemInit(), Exec_ListenPreCommit(), and SignalBackends().
| #define QUEUE_BACKEND_POS | ( | i | ) | (asyncQueueControl->backend[i].pos) |
Definition at line 247 of file async.c.
Referenced by asyncQueueAdvanceTail(), asyncQueueFillWarning(), asyncQueueReadAllNotifications(), asyncQueueUnregister(), AsyncShmemInit(), Exec_ListenPreCommit(), and SignalBackends().
| #define QUEUE_FULL_WARN_INTERVAL 5000 |
Definition at line 256 of file async.c.
Referenced by asyncQueueFillWarning().
| #define QUEUE_HEAD (asyncQueueControl->head) |
Definition at line 244 of file async.c.
Referenced by asyncQueueAddEntries(), asyncQueueFillWarning(), asyncQueueIsFull(), AsyncShmemInit(), and SignalBackends().
| #define QUEUE_MAX_PAGE (SLRU_PAGES_PER_SEGMENT * 0x10000 - 1) |
Definition at line 275 of file async.c.
Referenced by asyncQueueAdvance(), asyncQueueFillWarning(), asyncQueueIsFull(), and asyncQueuePagePrecedes().
| #define QUEUE_PAGESIZE BLCKSZ |
Definition at line 255 of file async.c.
Referenced by asyncQueueAddEntries(), asyncQueueAdvance(), and asyncQueueReadAllNotifications().
| #define QUEUE_POS_EQUAL | ( | x, | ||
| y | ||||
| ) | ((x).page == (y).page && (x).offset == (y).offset) |
Definition at line 192 of file async.c.
Referenced by asyncQueueFillWarning(), asyncQueueProcessPageEntries(), asyncQueueReadAllNotifications(), asyncQueueUnregister(), and SignalBackends().
| #define QUEUE_POS_MIN | ( | x, | ||
| y | ||||
| ) |
(asyncQueuePagePrecedes((x).page, (y).page) ? (x) : \ (x).page != (y).page ? (y) : \ (x).offset < (y).offset ? (x) : (y))
Definition at line 196 of file async.c.
Referenced by asyncQueueAdvanceTail(), and asyncQueueFillWarning().
| #define QUEUE_POS_OFFSET | ( | x | ) | ((x).offset) |
Definition at line 184 of file async.c.
Referenced by asyncQueueAddEntries(), asyncQueueAdvance(), asyncQueueProcessPageEntries(), and asyncQueueReadAllNotifications().
| #define QUEUE_POS_PAGE | ( | x | ) | ((x).page) |
Definition at line 183 of file async.c.
Referenced by asyncQueueAddEntries(), asyncQueueAdvance(), asyncQueueAdvanceTail(), asyncQueueFillWarning(), asyncQueueIsFull(), asyncQueueReadAllNotifications(), and AsyncShmemInit().
| #define QUEUE_TAIL (asyncQueueControl->tail) |
Definition at line 245 of file async.c.
Referenced by asyncQueueAdvanceTail(), asyncQueueFillWarning(), asyncQueueIsFull(), asyncQueueReadAllNotifications(), and AsyncShmemInit().
| #define QUEUEALIGN | ( | len | ) | INTALIGN(len) |
Definition at line 170 of file async.c.
Referenced by asyncQueueAdvance(), and asyncQueueNotificationToEntry().
| #define SET_QUEUE_POS | ( | x, | ||
| y, | ||||
| z | ||||
| ) |
do { \ (x).page = (y); \ (x).offset = (z); \ } while (0)
Definition at line 186 of file async.c.
Referenced by asyncQueueAdvance(), and AsyncShmemInit().
| typedef struct AsyncQueueControl AsyncQueueControl |
| typedef struct AsyncQueueEntry AsyncQueueEntry |
| typedef struct Notification Notification |
| typedef struct QueueBackendStatus QueueBackendStatus |
| typedef struct QueuePosition QueuePosition |
| enum ListenActionKind |
Definition at line 294 of file async.c.
{
LISTEN_LISTEN,
LISTEN_UNLISTEN,
LISTEN_UNLISTEN_ALL
} ListenActionKind;
| void Async_Listen | ( | const char * | channel | ) |
Definition at line 625 of file async.c.
References DEBUG1, elog, LISTEN_LISTEN, MyProcPid, queue_listen(), and Trace_notify.
Referenced by standard_ProcessUtility().
{
if (Trace_notify)
elog(DEBUG1, "Async_Listen(%s,%d)", channel, MyProcPid);
queue_listen(LISTEN_LISTEN, channel);
}
| void Async_Notify | ( | const char * | channel, | |
| const char * | payload | |||
| ) |
Definition at line 534 of file async.c.
References AsyncExistsPendingNotify(), Notification::channel, CurTransactionContext, DEBUG1, elog, ereport, errcode(), errmsg(), ERROR, lappend(), MemoryContextSwitchTo(), NAMEDATALEN, NOTIFY_PAYLOAD_MAX_LENGTH, palloc(), Notification::payload, pstrdup(), and Trace_notify.
Referenced by pg_notify(), standard_ProcessUtility(), and triggered_change_notification().
{
Notification *n;
MemoryContext oldcontext;
if (Trace_notify)
elog(DEBUG1, "Async_Notify(%s)", channel);
/* a channel name must be specified */
if (!channel || !strlen(channel))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("channel name cannot be empty")));
if (strlen(channel) >= NAMEDATALEN)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("channel name too long")));
if (payload)
{
if (strlen(payload) >= NOTIFY_PAYLOAD_MAX_LENGTH)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("payload string too long")));
}
/* no point in making duplicate entries in the list ... */
if (AsyncExistsPendingNotify(channel, payload))
return;
/*
* The notification list needs to live until end of transaction, so store
* it in the transaction context.
*/
oldcontext = MemoryContextSwitchTo(CurTransactionContext);
n = (Notification *) palloc(sizeof(Notification));
n->channel = pstrdup(channel);
if (payload)
n->payload = pstrdup(payload);
else
n->payload = "";
/*
* We want to preserve the order so we need to append every notification.
* See comments at AsyncExistsPendingNotify().
*/
pendingNotifies = lappend(pendingNotifies, n);
MemoryContextSwitchTo(oldcontext);
}
| void Async_Unlisten | ( | const char * | channel | ) |
Definition at line 639 of file async.c.
References DEBUG1, elog, LISTEN_UNLISTEN, MyProcPid, NIL, queue_listen(), Trace_notify, and unlistenExitRegistered.
Referenced by standard_ProcessUtility().
{
if (Trace_notify)
elog(DEBUG1, "Async_Unlisten(%s,%d)", channel, MyProcPid);
/* If we couldn't possibly be listening, no need to queue anything */
if (pendingActions == NIL && !unlistenExitRegistered)
return;
queue_listen(LISTEN_UNLISTEN, channel);
}
| void Async_UnlistenAll | ( | void | ) |
Definition at line 657 of file async.c.
References DEBUG1, elog, LISTEN_UNLISTEN_ALL, MyProcPid, NIL, queue_listen(), Trace_notify, and unlistenExitRegistered.
Referenced by DiscardAll(), and standard_ProcessUtility().
{
if (Trace_notify)
elog(DEBUG1, "Async_UnlistenAll(%d)", MyProcPid);
/* If we couldn't possibly be listening, no need to queue anything */
if (pendingActions == NIL && !unlistenExitRegistered)
return;
queue_listen(LISTEN_UNLISTEN_ALL, "");
}
| static void Async_UnlistenOnExit | ( | int | code, | |
| Datum | arg | |||
| ) | [static] |
Definition at line 724 of file async.c.
References asyncQueueUnregister(), and Exec_UnlistenAllCommit().
Referenced by Exec_ListenPreCommit().
{
Exec_UnlistenAllCommit();
asyncQueueUnregister();
}
| static bool AsyncExistsPendingNotify | ( | const char * | channel, | |
| const char * | payload | |||
| ) | [static] |
Definition at line 2150 of file async.c.
References Notification::channel, lfirst, llast, NIL, NULL, and Notification::payload.
Referenced by Async_Notify().
{
ListCell *p;
Notification *n;
if (pendingNotifies == NIL)
return false;
if (payload == NULL)
payload = "";
/*----------
* We need to append new elements to the end of the list in order to keep
* the order. However, on the other hand we'd like to check the list
* backwards in order to make duplicate-elimination a tad faster when the
* same condition is signaled many times in a row. So as a compromise we
* check the tail element first which we can access directly. If this
* doesn't match, we check the whole list.
*
* As we are not checking our parents' lists, we can still get duplicates
* in combination with subtransactions, like in:
*
* begin;
* notify foo '1';
* savepoint foo;
* notify foo '1';
* commit;
*----------
*/
n = (Notification *) llast(pendingNotifies);
if (strcmp(n->channel, channel) == 0 &&
strcmp(n->payload, payload) == 0)
return true;
foreach(p, pendingNotifies)
{
n = (Notification *) lfirst(p);
if (strcmp(n->channel, channel) == 0 &&
strcmp(n->payload, payload) == 0)
return true;
}
return false;
}
Definition at line 1278 of file async.c.
References AsyncCtl, AsyncCtlLock, asyncQueueAdvance(), asyncQueueNotificationToEntry(), AsyncQueueEntry::data, AsyncQueueEntry::dboid, InvalidTransactionId, AsyncQueueEntry::length, lfirst, lnext, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), NULL, QUEUE_HEAD, QUEUE_PAGESIZE, QUEUE_POS_OFFSET, QUEUE_POS_PAGE, SimpleLruReadPage(), and SimpleLruZeroPage().
Referenced by PreCommit_Notify().
{
AsyncQueueEntry qe;
QueuePosition queue_head;
int pageno;
int offset;
int slotno;
/* We hold both AsyncQueueLock and AsyncCtlLock during this operation */
LWLockAcquire(AsyncCtlLock, LW_EXCLUSIVE);
/*
* We work with a local copy of QUEUE_HEAD, which we write back to shared
* memory upon exiting. The reason for this is that if we have to advance
* to a new page, SimpleLruZeroPage might fail (out of disk space, for
* instance), and we must not advance QUEUE_HEAD if it does. (Otherwise,
* subsequent insertions would try to put entries into a page that slru.c
* thinks doesn't exist yet.) So, use a local position variable. Note
* that if we do fail, any already-inserted queue entries are forgotten;
* this is okay, since they'd be useless anyway after our transaction
* rolls back.
*/
queue_head = QUEUE_HEAD;
/* Fetch the current page */
pageno = QUEUE_POS_PAGE(queue_head);
slotno = SimpleLruReadPage(AsyncCtl, pageno, true, InvalidTransactionId);
/* Note we mark the page dirty before writing in it */
AsyncCtl->shared->page_dirty[slotno] = true;
while (nextNotify != NULL)
{
Notification *n = (Notification *) lfirst(nextNotify);
/* Construct a valid queue entry in local variable qe */
asyncQueueNotificationToEntry(n, &qe);
offset = QUEUE_POS_OFFSET(queue_head);
/* Check whether the entry really fits on the current page */
if (offset + qe.length <= QUEUE_PAGESIZE)
{
/* OK, so advance nextNotify past this item */
nextNotify = lnext(nextNotify);
}
else
{
/*
* Write a dummy entry to fill up the page. Actually readers will
* only check dboid and since it won't match any reader's database
* OID, they will ignore this entry and move on.
*/
qe.length = QUEUE_PAGESIZE - offset;
qe.dboid = InvalidOid;
qe.data[0] = '\0'; /* empty channel */
qe.data[1] = '\0'; /* empty payload */
}
/* Now copy qe into the shared buffer page */
memcpy(AsyncCtl->shared->page_buffer[slotno] + offset,
&qe,
qe.length);
/* Advance queue_head appropriately, and detect if page is full */
if (asyncQueueAdvance(&(queue_head), qe.length))
{
/*
* Page is full, so we're done here, but first fill the next page
* with zeroes. The reason to do this is to ensure that slru.c's
* idea of the head page is always the same as ours, which avoids
* boundary problems in SimpleLruTruncate. The test in
* asyncQueueIsFull() ensured that there is room to create this
* page without overrunning the queue.
*/
slotno = SimpleLruZeroPage(AsyncCtl, QUEUE_POS_PAGE(queue_head));
/* And exit the loop */
break;
}
}
/* Success, so update the global QUEUE_HEAD */
QUEUE_HEAD = queue_head;
LWLockRelease(AsyncCtlLock);
return nextNotify;
}
| static bool asyncQueueAdvance | ( | QueuePosition * | position, | |
| int | entryLength | |||
| ) | [static] |
Definition at line 1206 of file async.c.
References Assert, AsyncQueueEntryEmptySize, QUEUE_MAX_PAGE, QUEUE_PAGESIZE, QUEUE_POS_OFFSET, QUEUE_POS_PAGE, QUEUEALIGN, and SET_QUEUE_POS.
Referenced by asyncQueueAddEntries(), and asyncQueueProcessPageEntries().
{
int pageno = QUEUE_POS_PAGE(*position);
int offset = QUEUE_POS_OFFSET(*position);
bool pageJump = false;
/*
* Move to the next writing position: First jump over what we have just
* written or read.
*/
offset += entryLength;
Assert(offset <= QUEUE_PAGESIZE);
/*
* In a second step check if another entry can possibly be written to the
* page. If so, stay here, we have reached the next position. If not, then
* we need to move on to the next page.
*/
if (offset + QUEUEALIGN(AsyncQueueEntryEmptySize) > QUEUE_PAGESIZE)
{
pageno++;
if (pageno > QUEUE_MAX_PAGE)
pageno = 0; /* wrap around */
offset = 0;
pageJump = true;
}
SET_QUEUE_POS(*position, pageno, offset);
return pageJump;
}
| static void asyncQueueAdvanceTail | ( | void | ) | [static] |
Definition at line 2028 of file async.c.
References AsyncCtl, AsyncQueueLock, asyncQueuePagePrecedes(), i, InvalidPid, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MaxBackends, QUEUE_BACKEND_PID, QUEUE_BACKEND_POS, QUEUE_POS_MIN, QUEUE_POS_PAGE, QUEUE_TAIL, and SimpleLruTruncate().
Referenced by asyncQueueReadAllNotifications(), asyncQueueUnregister(), and ProcessCompletedNotifies().
{
QueuePosition min;
int i;
int oldtailpage;
int newtailpage;
int boundary;
LWLockAcquire(AsyncQueueLock, LW_EXCLUSIVE);
min = QUEUE_HEAD;
for (i = 1; i <= MaxBackends; i++)
{
if (QUEUE_BACKEND_PID(i) != InvalidPid)
min = QUEUE_POS_MIN(min, QUEUE_BACKEND_POS(i));
}
oldtailpage = QUEUE_POS_PAGE(QUEUE_TAIL);
QUEUE_TAIL = min;
LWLockRelease(AsyncQueueLock);
/*
* We can truncate something if the global tail advanced across an SLRU
* segment boundary.
*
* XXX it might be better to truncate only once every several segments, to
* reduce the number of directory scans.
*/
newtailpage = QUEUE_POS_PAGE(min);
boundary = newtailpage - (newtailpage % SLRU_PAGES_PER_SEGMENT);
if (asyncQueuePagePrecedes(oldtailpage, boundary))
{
/*
* SimpleLruTruncate() will ask for AsyncCtlLock but will also release
* the lock again.
*/
SimpleLruTruncate(AsyncCtl, newtailpage);
}
}
| static void asyncQueueFillWarning | ( | void | ) | [static] |
Definition at line 1375 of file async.c.
References ereport, errdetail(), errhint(), errmsg(), GetCurrentTimestamp(), i, InvalidPid, AsyncQueueControl::lastQueueFillWarn, MaxBackends, QUEUE_BACKEND_PID, QUEUE_BACKEND_POS, QUEUE_FULL_WARN_INTERVAL, QUEUE_HEAD, QUEUE_MAX_PAGE, QUEUE_POS_EQUAL, QUEUE_POS_MIN, QUEUE_POS_PAGE, QUEUE_TAIL, TimestampDifferenceExceeds(), and WARNING.
Referenced by PreCommit_Notify().
{
int headPage = QUEUE_POS_PAGE(QUEUE_HEAD);
int tailPage = QUEUE_POS_PAGE(QUEUE_TAIL);
int occupied;
double fillDegree;
TimestampTz t;
occupied = headPage - tailPage;
if (occupied == 0)
return; /* fast exit for common case */
if (occupied < 0)
{
/* head has wrapped around, tail not yet */
occupied += QUEUE_MAX_PAGE + 1;
}
fillDegree = (double) occupied / (double) ((QUEUE_MAX_PAGE + 1) / 2);
if (fillDegree < 0.5)
return;
t = GetCurrentTimestamp();
if (TimestampDifferenceExceeds(asyncQueueControl->lastQueueFillWarn,
t, QUEUE_FULL_WARN_INTERVAL))
{
QueuePosition min = QUEUE_HEAD;
int32 minPid = InvalidPid;
int i;
for (i = 1; i <= MaxBackends; i++)
{
if (QUEUE_BACKEND_PID(i) != InvalidPid)
{
min = QUEUE_POS_MIN(min, QUEUE_BACKEND_POS(i));
if (QUEUE_POS_EQUAL(min, QUEUE_BACKEND_POS(i)))
minPid = QUEUE_BACKEND_PID(i);
}
}
ereport(WARNING,
(errmsg("NOTIFY queue is %.0f%% full", fillDegree * 100),
(minPid != InvalidPid ?
errdetail("The server process with PID %d is among those with the oldest transactions.", minPid)
: 0),
(minPid != InvalidPid ?
errhint("The NOTIFY queue cannot be emptied until that process ends its current transaction.")
: 0)));
asyncQueueControl->lastQueueFillWarn = t;
}
}
| static bool asyncQueueIsFull | ( | void | ) | [static] |
Definition at line 1175 of file async.c.
References asyncQueuePagePrecedes(), QUEUE_HEAD, QUEUE_MAX_PAGE, QUEUE_POS_PAGE, and QUEUE_TAIL.
Referenced by PreCommit_Notify().
{
int nexthead;
int boundary;
/*
* The queue is full if creating a new head page would create a page that
* logically precedes the current global tail pointer, ie, the head
* pointer would wrap around compared to the tail. We cannot create such
* a head page for fear of confusing slru.c. For safety we round the tail
* pointer back to a segment boundary (compare the truncation logic in
* asyncQueueAdvanceTail).
*
* Note that this test is *not* dependent on how much space there is on
* the current head page. This is necessary because asyncQueueAddEntries
* might try to create the next head page in any case.
*/
nexthead = QUEUE_POS_PAGE(QUEUE_HEAD) + 1;
if (nexthead > QUEUE_MAX_PAGE)
nexthead = 0; /* wrap around */
boundary = QUEUE_POS_PAGE(QUEUE_TAIL);
boundary -= boundary % SLRU_PAGES_PER_SEGMENT;
return asyncQueuePagePrecedes(nexthead, boundary);
}
| static void asyncQueueNotificationToEntry | ( | Notification * | n, | |
| AsyncQueueEntry * | qe | |||
| ) | [static] |
Definition at line 1241 of file async.c.
References Assert, AsyncQueueEntryEmptySize, Notification::channel, AsyncQueueEntry::data, AsyncQueueEntry::dboid, GetCurrentTransactionId(), AsyncQueueEntry::length, MyDatabaseId, MyProcPid, NAMEDATALEN, NOTIFY_PAYLOAD_MAX_LENGTH, Notification::payload, QUEUEALIGN, AsyncQueueEntry::srcPid, and AsyncQueueEntry::xid.
Referenced by asyncQueueAddEntries().
{
size_t channellen = strlen(n->channel);
size_t payloadlen = strlen(n->payload);
int entryLength;
Assert(channellen < NAMEDATALEN);
Assert(payloadlen < NOTIFY_PAYLOAD_MAX_LENGTH);
/* The terminators are already included in AsyncQueueEntryEmptySize */
entryLength = AsyncQueueEntryEmptySize + payloadlen + channellen;
entryLength = QUEUEALIGN(entryLength);
qe->length = entryLength;
qe->dboid = MyDatabaseId;
qe->xid = GetCurrentTransactionId();
qe->srcPid = MyProcPid;
memcpy(qe->data, n->channel, channellen + 1);
memcpy(qe->data + channellen + 1, n->payload, payloadlen + 1);
}
| static bool asyncQueuePagePrecedes | ( | int | p, | |
| int | q | |||
| ) | [static] |
Definition at line 394 of file async.c.
References Assert, and QUEUE_MAX_PAGE.
Referenced by asyncQueueAdvanceTail(), and asyncQueueIsFull().
{
int diff;
/*
* We have to compare modulo (QUEUE_MAX_PAGE+1)/2. Both inputs should be
* in the range 0..QUEUE_MAX_PAGE.
*/
Assert(p >= 0 && p <= QUEUE_MAX_PAGE);
Assert(q >= 0 && q <= QUEUE_MAX_PAGE);
diff = p - q;
if (diff >= ((QUEUE_MAX_PAGE + 1) / 2))
diff -= QUEUE_MAX_PAGE + 1;
else if (diff < -((QUEUE_MAX_PAGE + 1) / 2))
diff += QUEUE_MAX_PAGE + 1;
return diff < 0;
}
| static bool asyncQueueProcessPageEntries | ( | QueuePosition * | current, | |
| QueuePosition | stop, | |||
| char * | page_buffer | |||
| ) | [static] |
Definition at line 1950 of file async.c.
References asyncQueueAdvance(), AsyncQueueEntry::data, AsyncQueueEntry::dboid, IsListeningOn(), AsyncQueueEntry::length, MyDatabaseId, NotifyMyFrontEnd(), QUEUE_POS_EQUAL, QUEUE_POS_OFFSET, AsyncQueueEntry::srcPid, TransactionIdDidAbort(), TransactionIdDidCommit(), and AsyncQueueEntry::xid.
Referenced by asyncQueueReadAllNotifications().
{
bool reachedStop = false;
bool reachedEndOfPage;
AsyncQueueEntry *qe;
do
{
QueuePosition thisentry = *current;
if (QUEUE_POS_EQUAL(thisentry, stop))
break;
qe = (AsyncQueueEntry *) (page_buffer + QUEUE_POS_OFFSET(thisentry));
/*
* Advance *current over this message, possibly to the next page. As
* noted in the comments for asyncQueueReadAllNotifications, we must
* do this before possibly failing while processing the message.
*/
reachedEndOfPage = asyncQueueAdvance(current, qe->length);
/* Ignore messages destined for other databases */
if (qe->dboid == MyDatabaseId)
{
if (TransactionIdDidCommit(qe->xid))
{
/* qe->data is the null-terminated channel name */
char *channel = qe->data;
if (IsListeningOn(channel))
{
/* payload follows channel name */
char *payload = qe->data + strlen(channel) + 1;
NotifyMyFrontEnd(channel, payload, qe->srcPid);
}
}
else if (TransactionIdDidAbort(qe->xid))
{
/*
* If the source transaction aborted, we just ignore its
* notifications.
*/
}
else
{
/*
* The transaction has neither committed nor aborted so far,
* so we can't process its message yet. Break out of the
* loop, but first back up *current so we will reprocess the
* message next time. (Note: it is unlikely but not
* impossible for TransactionIdDidCommit to fail, so we can't
* really avoid this advance-then-back-up behavior when
* dealing with an uncommitted message.)
*/
*current = thisentry;
reachedStop = true;
break;
}
}
/* Loop back if we're not at end of page */
} while (!reachedEndOfPage);
if (QUEUE_POS_EQUAL(*current, stop))
reachedStop = true;
return reachedStop;
}
| static void asyncQueueReadAllNotifications | ( | void | ) | [static] |
Definition at line 1788 of file async.c.
References Assert, AsyncCtl, AsyncCtlLock, asyncQueueAdvanceTail(), AsyncQueueLock, asyncQueueProcessPageEntries(), buf, InvalidTransactionId, LW_SHARED, LWLockAcquire(), LWLockRelease(), MyBackendId, MyProcPid, PG_CATCH, PG_END_TRY, PG_RE_THROW, PG_TRY, QUEUE_BACKEND_PID, QUEUE_BACKEND_POS, QUEUE_PAGESIZE, QUEUE_POS_EQUAL, QUEUE_POS_OFFSET, QUEUE_POS_PAGE, QUEUE_TAIL, and SimpleLruReadPage_ReadOnly().
Referenced by Exec_ListenPreCommit(), ProcessCompletedNotifies(), and ProcessIncomingNotify().
{
QueuePosition pos;
QueuePosition oldpos;
QueuePosition head;
bool advanceTail;
/* page_buffer must be adequately aligned, so use a union */
union
{
char buf[QUEUE_PAGESIZE];
AsyncQueueEntry align;
} page_buffer;
/* Fetch current state */
LWLockAcquire(AsyncQueueLock, LW_SHARED);
/* Assert checks that we have a valid state entry */
Assert(MyProcPid == QUEUE_BACKEND_PID(MyBackendId));
pos = oldpos = QUEUE_BACKEND_POS(MyBackendId);
head = QUEUE_HEAD;
LWLockRelease(AsyncQueueLock);
if (QUEUE_POS_EQUAL(pos, head))
{
/* Nothing to do, we have read all notifications already. */
return;
}
/*----------
* Note that we deliver everything that we see in the queue and that
* matches our _current_ listening state.
* Especially we do not take into account different commit times.
* Consider the following example:
*
* Backend 1: Backend 2:
*
* transaction starts
* NOTIFY foo;
* commit starts
* transaction starts
* LISTEN foo;
* commit starts
* commit to clog
* commit to clog
*
* It could happen that backend 2 sees the notification from backend 1 in
* the queue. Even though the notifying transaction committed before
* the listening transaction, we still deliver the notification.
*
* The idea is that an additional notification does not do any harm, we
* just need to make sure that we do not miss a notification.
*
* It is possible that we fail while trying to send a message to our
* frontend (for example, because of encoding conversion failure).
* If that happens it is critical that we not try to send the same
* message over and over again. Therefore, we place a PG_TRY block
* here that will forcibly advance our backend position before we lose
* control to an error. (We could alternatively retake AsyncQueueLock
* and move the position before handling each individual message, but
* that seems like too much lock traffic.)
*----------
*/
PG_TRY();
{
bool reachedStop;
do
{
int curpage = QUEUE_POS_PAGE(pos);
int curoffset = QUEUE_POS_OFFSET(pos);
int slotno;
int copysize;
/*
* We copy the data from SLRU into a local buffer, so as to avoid
* holding the AsyncCtlLock while we are examining the entries and
* possibly transmitting them to our frontend. Copy only the part
* of the page we will actually inspect.
*/
slotno = SimpleLruReadPage_ReadOnly(AsyncCtl, curpage,
InvalidTransactionId);
if (curpage == QUEUE_POS_PAGE(head))
{
/* we only want to read as far as head */
copysize = QUEUE_POS_OFFSET(head) - curoffset;
if (copysize < 0)
copysize = 0; /* just for safety */
}
else
{
/* fetch all the rest of the page */
copysize = QUEUE_PAGESIZE - curoffset;
}
memcpy(page_buffer.buf + curoffset,
AsyncCtl->shared->page_buffer[slotno] + curoffset,
copysize);
/* Release lock that we got from SimpleLruReadPage_ReadOnly() */
LWLockRelease(AsyncCtlLock);
/*
* Process messages up to the stop position, end of page, or an
* uncommitted message.
*
* Our stop position is what we found to be the head's position
* when we entered this function. It might have changed already.
* But if it has, we will receive (or have already received and
* queued) another signal and come here again.
*
* We are not holding AsyncQueueLock here! The queue can only
* extend beyond the head pointer (see above) and we leave our
* backend's pointer where it is so nobody will truncate or
* rewrite pages under us. Especially we don't want to hold a lock
* while sending the notifications to the frontend.
*/
reachedStop = asyncQueueProcessPageEntries(&pos, head,
page_buffer.buf);
} while (!reachedStop);
}
PG_CATCH();
{
/* Update shared state */
LWLockAcquire(AsyncQueueLock, LW_SHARED);
QUEUE_BACKEND_POS(MyBackendId) = pos;
advanceTail = QUEUE_POS_EQUAL(oldpos, QUEUE_TAIL);
LWLockRelease(AsyncQueueLock);
/* If we were the laziest backend, try to advance the tail pointer */
if (advanceTail)
asyncQueueAdvanceTail();
PG_RE_THROW();
}
PG_END_TRY();
/* Update shared state */
LWLockAcquire(AsyncQueueLock, LW_SHARED);
QUEUE_BACKEND_POS(MyBackendId) = pos;
advanceTail = QUEUE_POS_EQUAL(oldpos, QUEUE_TAIL);
LWLockRelease(AsyncQueueLock);
/* If we were the laziest backend, try to advance the tail pointer */
if (advanceTail)
asyncQueueAdvanceTail();
}
| static void asyncQueueUnregister | ( | void | ) | [static] |
Definition at line 1144 of file async.c.
References amRegisteredListener, Assert, asyncQueueAdvanceTail(), AsyncQueueLock, LW_SHARED, LWLockAcquire(), LWLockRelease(), MyBackendId, MyProcPid, NIL, QUEUE_BACKEND_PID, QUEUE_BACKEND_POS, and QUEUE_POS_EQUAL.
Referenced by Async_UnlistenOnExit(), AtAbort_Notify(), and AtCommit_Notify().
{
bool advanceTail;
Assert(listenChannels == NIL); /* else caller error */
if (!amRegisteredListener) /* nothing to do */
return;
LWLockAcquire(AsyncQueueLock, LW_SHARED);
/* check if entry is valid and oldest ... */
advanceTail = (MyProcPid == QUEUE_BACKEND_PID(MyBackendId)) &&
QUEUE_POS_EQUAL(QUEUE_BACKEND_POS(MyBackendId), QUEUE_TAIL);
/* ... then mark it invalid */
QUEUE_BACKEND_PID(MyBackendId) = InvalidPid;
LWLockRelease(AsyncQueueLock);
/* mark ourselves as no longer listed in the global array */
amRegisteredListener = false;
/* If we were the laziest backend, try to advance the tail pointer */
if (advanceTail)
asyncQueueAdvanceTail();
}
| void AsyncShmemInit | ( | void | ) |
Definition at line 434 of file async.c.
References add_size(), AsyncCtl, AsyncCtlLock, i, AsyncQueueControl::lastQueueFillWarn, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MaxBackends, mul_size(), NULL, NUM_ASYNC_BUFFERS, QUEUE_BACKEND_PID, QUEUE_BACKEND_POS, QUEUE_HEAD, QUEUE_POS_PAGE, QUEUE_TAIL, SET_QUEUE_POS, ShmemInitStruct(), SimpleLruInit(), SimpleLruWritePage(), SimpleLruZeroPage(), SlruScanDirCbDeleteAll(), and SlruScanDirectory().
Referenced by CreateSharedMemoryAndSemaphores().
{
bool found;
int slotno;
Size size;
/*
* Create or attach to the AsyncQueueControl structure.
*
* The used entries in the backend[] array run from 1 to MaxBackends.
* sizeof(AsyncQueueControl) already includes space for the unused zero'th
* entry, but we need to add on space for the used entries.
*/
size = mul_size(MaxBackends, sizeof(QueueBackendStatus));
size = add_size(size, sizeof(AsyncQueueControl));
asyncQueueControl = (AsyncQueueControl *)
ShmemInitStruct("Async Queue Control", size, &found);
if (!found)
{
/* First time through, so initialize it */
int i;
SET_QUEUE_POS(QUEUE_HEAD, 0, 0);
SET_QUEUE_POS(QUEUE_TAIL, 0, 0);
asyncQueueControl->lastQueueFillWarn = 0;
/* zero'th entry won't be used, but let's initialize it anyway */
for (i = 0; i <= MaxBackends; i++)
{
QUEUE_BACKEND_PID(i) = InvalidPid;
SET_QUEUE_POS(QUEUE_BACKEND_POS(i), 0, 0);
}
}
/*
* Set up SLRU management of the pg_notify data.
*/
AsyncCtl->PagePrecedes = asyncQueuePagePrecedes;
SimpleLruInit(AsyncCtl, "Async Ctl", NUM_ASYNC_BUFFERS, 0,
AsyncCtlLock, "pg_notify");
/* Override default assumption that writes should be fsync'd */
AsyncCtl->do_fsync = false;
if (!found)
{
/*
* During start or reboot, clean out the pg_notify directory.
*/
(void) SlruScanDirectory(AsyncCtl, SlruScanDirCbDeleteAll, NULL);
/* Now initialize page zero to empty */
LWLockAcquire(AsyncCtlLock, LW_EXCLUSIVE);
slotno = SimpleLruZeroPage(AsyncCtl, QUEUE_POS_PAGE(QUEUE_HEAD));
/* This write is just to verify that pg_notify/ is writable */
SimpleLruWritePage(AsyncCtl, slotno);
LWLockRelease(AsyncCtlLock);
}
}
| Size AsyncShmemSize | ( | void | ) |
Definition at line 417 of file async.c.
References add_size(), MaxBackends, mul_size(), NUM_ASYNC_BUFFERS, and SimpleLruShmemSize().
Referenced by CreateSharedMemoryAndSemaphores().
{
Size size;
/* This had better match AsyncShmemInit */
size = mul_size(MaxBackends, sizeof(QueueBackendStatus));
size = add_size(size, sizeof(AsyncQueueControl));
size = add_size(size, SimpleLruShmemSize(NUM_ASYNC_BUFFERS, 0));
return size;
}
| void AtAbort_Notify | ( | void | ) |
Definition at line 1517 of file async.c.
References amRegisteredListener, asyncQueueUnregister(), ClearPendingActionsAndNotifies(), and NIL.
Referenced by AbortTransaction().
{
/*
* If we LISTEN but then roll back the transaction after PreCommit_Notify,
* we have registered as a listener but have not made any entry in
* listenChannels. In that case, deregister again.
*/
if (amRegisteredListener && listenChannels == NIL)
asyncQueueUnregister();
/* And clean up */
ClearPendingActionsAndNotifies();
}
| void AtCommit_Notify | ( | void | ) |
Definition at line 861 of file async.c.
References ListenAction::action, amRegisteredListener, asyncQueueUnregister(), ListenAction::channel, ClearPendingActionsAndNotifies(), DEBUG1, elog, Exec_ListenCommit(), Exec_UnlistenAllCommit(), Exec_UnlistenCommit(), lfirst, LISTEN_LISTEN, LISTEN_UNLISTEN, LISTEN_UNLISTEN_ALL, NIL, and Trace_notify.
Referenced by CommitTransaction().
{
ListCell *p;
/*
* Allow transactions that have not executed LISTEN/UNLISTEN/NOTIFY to
* return as soon as possible
*/
if (!pendingActions && !pendingNotifies)
return;
if (Trace_notify)
elog(DEBUG1, "AtCommit_Notify");
/* Perform any pending listen/unlisten actions */
foreach(p, pendingActions)
{
ListenAction *actrec = (ListenAction *) lfirst(p);
switch (actrec->action)
{
case LISTEN_LISTEN:
Exec_ListenCommit(actrec->channel);
break;
case LISTEN_UNLISTEN:
Exec_UnlistenCommit(actrec->channel);
break;
case LISTEN_UNLISTEN_ALL:
Exec_UnlistenAllCommit();
break;
}
}
/* If no longer listening to anything, get out of listener array */
if (amRegisteredListener && listenChannels == NIL)
asyncQueueUnregister();
/* And clean up */
ClearPendingActionsAndNotifies();
}
| void AtPrepare_Notify | ( | void | ) |
Definition at line 737 of file async.c.
References ereport, errcode(), errmsg(), and ERROR.
Referenced by PrepareTransaction().
{
/* It's not allowed to have any pending LISTEN/UNLISTEN/NOTIFY actions */
if (pendingActions || pendingNotifies)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot PREPARE a transaction that has executed LISTEN, UNLISTEN, or NOTIFY")));
}
| void AtSubAbort_Notify | ( | void | ) |
Definition at line 1599 of file async.c.
References GetCurrentTransactionNestLevel(), linitial, list_delete_first(), and list_length().
Referenced by AbortSubTransaction().
{
int my_level = GetCurrentTransactionNestLevel();
/*
* All we have to do is pop the stack --- the actions/notifies made in
* this subxact are no longer interesting, and the space will be freed
* when CurTransactionContext is recycled.
*
* This routine could be called more than once at a given nesting level if
* there is trouble during subxact abort. Avoid dumping core by using
* GetCurrentTransactionNestLevel as the indicator of how far we need to
* prune the list.
*/
while (list_length(upperPendingActions) > my_level - 2)
{
pendingActions = (List *) linitial(upperPendingActions);
upperPendingActions = list_delete_first(upperPendingActions);
}
while (list_length(upperPendingNotifies) > my_level - 2)
{
pendingNotifies = (List *) linitial(upperPendingNotifies);
upperPendingNotifies = list_delete_first(upperPendingNotifies);
}
}
| void AtSubCommit_Notify | ( | void | ) |
Definition at line 1567 of file async.c.
References Assert, GetCurrentTransactionNestLevel(), linitial, list_concat(), list_delete_first(), and list_length().
Referenced by CommitSubTransaction().
{
List *parentPendingActions;
List *parentPendingNotifies;
parentPendingActions = (List *) linitial(upperPendingActions);
upperPendingActions = list_delete_first(upperPendingActions);
Assert(list_length(upperPendingActions) ==
GetCurrentTransactionNestLevel() - 2);
/*
* Mustn't try to eliminate duplicates here --- see queue_listen()
*/
pendingActions = list_concat(parentPendingActions, pendingActions);
parentPendingNotifies = (List *) linitial(upperPendingNotifies);
upperPendingNotifies = list_delete_first(upperPendingNotifies);
Assert(list_length(upperPendingNotifies) ==
GetCurrentTransactionNestLevel() - 2);
/*
* We could try to eliminate duplicates here, but it seems not worthwhile.
*/
pendingNotifies = list_concat(parentPendingNotifies, pendingNotifies);
}
| void AtSubStart_Notify | ( | void | ) |
Definition at line 1537 of file async.c.
References Assert, GetCurrentTransactionNestLevel(), lcons(), list_length(), MemoryContextSwitchTo(), and TopTransactionContext.
Referenced by StartSubTransaction().
{
MemoryContext old_cxt;
/* Keep the list-of-lists in TopTransactionContext for simplicity */
old_cxt = MemoryContextSwitchTo(TopTransactionContext);
upperPendingActions = lcons(pendingActions, upperPendingActions);
Assert(list_length(upperPendingActions) ==
GetCurrentTransactionNestLevel() - 1);
pendingActions = NIL;
upperPendingNotifies = lcons(pendingNotifies, upperPendingNotifies);
Assert(list_length(upperPendingNotifies) ==
GetCurrentTransactionNestLevel() - 1);
pendingNotifies = NIL;
MemoryContextSwitchTo(old_cxt);
}
| static void ClearPendingActionsAndNotifies | ( | void | ) | [static] |
Definition at line 2198 of file async.c.
Referenced by AtAbort_Notify(), and AtCommit_Notify().
{
/*
* We used to have to explicitly deallocate the list members and nodes,
* because they were malloc'd. Now, since we know they are palloc'd in
* CurTransactionContext, we need not do that --- they'll go away
* automatically at transaction exit. We need only reset the list head
* pointers.
*/
pendingActions = NIL;
pendingNotifies = NIL;
}
| bool DisableNotifyInterrupt | ( | void | ) |
Definition at line 1773 of file async.c.
References notifyInterruptEnabled.
Referenced by client_read_ended(), die(), PostgresMain(), ProcessCatchupEvent(), ProcessInterrupts(), RecoveryConflictInterrupt(), and StatementCancelHandler().
{
bool result = (notifyInterruptEnabled != 0);
notifyInterruptEnabled = 0;
return result;
}
| void EnableNotifyInterrupt | ( | void | ) |
Definition at line 1716 of file async.c.
References DEBUG1, elog, IsTransactionOrTransactionBlock(), notifyInterruptEnabled, notifyInterruptOccurred, ProcessIncomingNotify(), and Trace_notify.
Referenced by prepare_for_client_read(), and ProcessCatchupEvent().
{
if (IsTransactionOrTransactionBlock())
return; /* not really idle */
/*
* This code is tricky because we are communicating with a signal handler
* that could interrupt us at any point. If we just checked
* notifyInterruptOccurred and then set notifyInterruptEnabled, we could
* fail to respond promptly to a signal that happens in between those two
* steps. (A very small time window, perhaps, but Murphy's Law says you
* can hit it...) Instead, we first set the enable flag, then test the
* occurred flag. If we see an unserviced interrupt has occurred, we
* re-clear the enable flag before going off to do the service work. (That
* prevents re-entrant invocation of ProcessIncomingNotify() if another
* interrupt occurs.) If an interrupt comes in between the setting and
* clearing of notifyInterruptEnabled, then it will have done the service
* work and left notifyInterruptOccurred zero, so we have to check again
* after clearing enable. The whole thing has to be in a loop in case
* another interrupt occurs while we're servicing the first. Once we get
* out of the loop, enable is set and we know there is no unserviced
* interrupt.
*
* NB: an overenthusiastic optimizing compiler could easily break this
* code. Hopefully, they all understand what "volatile" means these days.
*/
for (;;)
{
notifyInterruptEnabled = 1;
if (!notifyInterruptOccurred)
break;
notifyInterruptEnabled = 0;
if (notifyInterruptOccurred)
{
if (Trace_notify)
elog(DEBUG1, "EnableNotifyInterrupt: perform async notify");
ProcessIncomingNotify();
if (Trace_notify)
elog(DEBUG1, "EnableNotifyInterrupt: done");
}
}
}
| static void Exec_ListenCommit | ( | const char * | channel | ) | [static] |
Definition at line 965 of file async.c.
References IsListeningOn(), lappend(), MemoryContextSwitchTo(), pstrdup(), and TopMemoryContext.
Referenced by AtCommit_Notify().
{
MemoryContext oldcontext;
/* Do nothing if we are already listening on this channel */
if (IsListeningOn(channel))
return;
/*
* Add the new channel name to listenChannels.
*
* XXX It is theoretically possible to get an out-of-memory failure here,
* which would be bad because we already committed. For the moment it
* doesn't seem worth trying to guard against that, but maybe improve this
* later.
*/
oldcontext = MemoryContextSwitchTo(TopMemoryContext);
listenChannels = lappend(listenChannels, pstrdup(channel));
MemoryContextSwitchTo(oldcontext);
}
| static void Exec_ListenPreCommit | ( | void | ) | [static] |
Definition at line 908 of file async.c.
References amRegisteredListener, Async_UnlistenOnExit(), AsyncQueueLock, asyncQueueReadAllNotifications(), DEBUG1, elog, LW_SHARED, LWLockAcquire(), LWLockRelease(), MyBackendId, MyProcPid, on_shmem_exit(), QUEUE_BACKEND_PID, QUEUE_BACKEND_POS, Trace_notify, and unlistenExitRegistered.
Referenced by PreCommit_Notify().
{
/*
* Nothing to do if we are already listening to something, nor if we
* already ran this routine in this transaction.
*/
if (amRegisteredListener)
return;
if (Trace_notify)
elog(DEBUG1, "Exec_ListenPreCommit(%d)", MyProcPid);
/*
* Before registering, make sure we will unlisten before dying. (Note:
* this action does not get undone if we abort later.)
*/
if (!unlistenExitRegistered)
{
on_shmem_exit(Async_UnlistenOnExit, 0);
unlistenExitRegistered = true;
}
/*
* This is our first LISTEN, so establish our pointer.
*
* We set our pointer to the global tail pointer and then move it forward
* over already-committed notifications. This ensures we cannot miss any
* not-yet-committed notifications. We might get a few more but that
* doesn't hurt.
*/
LWLockAcquire(AsyncQueueLock, LW_SHARED);
QUEUE_BACKEND_POS(MyBackendId) = QUEUE_TAIL;
QUEUE_BACKEND_PID(MyBackendId) = MyProcPid;
LWLockRelease(AsyncQueueLock);
/* Now we are listed in the global array, so remember we're listening */
amRegisteredListener = true;
/*
* Try to move our pointer forward as far as possible. This will skip over
* already-committed notifications. Still, we could get notifications that
* have already committed before we started to LISTEN.
*
* Note that we are not yet listening on anything, so we won't deliver any
* notification to the frontend.
*
* This will also advance the global tail pointer if possible.
*/
asyncQueueReadAllNotifications();
}
| static void Exec_UnlistenAllCommit | ( | void | ) | [static] |
Definition at line 1026 of file async.c.
References DEBUG1, elog, list_free_deep(), MyProcPid, and Trace_notify.
Referenced by Async_UnlistenOnExit(), and AtCommit_Notify().
{
if (Trace_notify)
elog(DEBUG1, "Exec_UnlistenAllCommit(%d)", MyProcPid);
list_free_deep(listenChannels);
listenChannels = NIL;
}
| static void Exec_UnlistenCommit | ( | const char * | channel | ) | [static] |
Definition at line 992 of file async.c.
References DEBUG1, elog, lfirst, list_delete_cell(), MyProcPid, pfree(), and Trace_notify.
Referenced by AtCommit_Notify().
{
ListCell *q;
ListCell *prev;
if (Trace_notify)
elog(DEBUG1, "Exec_UnlistenCommit(%s,%d)", channel, MyProcPid);
prev = NULL;
foreach(q, listenChannels)
{
char *lchan = (char *) lfirst(q);
if (strcmp(lchan, channel) == 0)
{
listenChannels = list_delete_cell(listenChannels, q, prev);
pfree(lchan);
break;
}
prev = q;
}
/*
* We do not complain about unlistening something not being listened;
* should we?
*/
}
| void HandleNotifyInterrupt | ( | void | ) |
Definition at line 1636 of file async.c.
References CHECK_FOR_INTERRUPTS, DEBUG1, elog, ImmediateInterruptOK, notifyInterruptEnabled, notifyInterruptOccurred, proc_exit_inprogress, ProcessIncomingNotify(), and Trace_notify.
Referenced by procsignal_sigusr1_handler().
{
/*
* Note: this is called by a SIGNAL HANDLER. You must be very wary what
* you do here. Some helpful soul had this routine sprinkled with
* TPRINTFs, which would likely lead to corruption of stdio buffers if
* they were ever turned on.
*/
/* Don't joggle the elbow of proc_exit */
if (proc_exit_inprogress)
return;
if (notifyInterruptEnabled)
{
bool save_ImmediateInterruptOK = ImmediateInterruptOK;
/*
* We may be called while ImmediateInterruptOK is true; turn it off
* while messing with the NOTIFY state. (We would have to save and
* restore it anyway, because PGSemaphore operations inside
* ProcessIncomingNotify() might reset it.)
*/
ImmediateInterruptOK = false;
/*
* I'm not sure whether some flavors of Unix might allow another
* SIGUSR1 occurrence to recursively interrupt this routine. To cope
* with the possibility, we do the same sort of dance that
* EnableNotifyInterrupt must do --- see that routine for comments.
*/
notifyInterruptEnabled = 0; /* disable any recursive signal */
notifyInterruptOccurred = 1; /* do at least one iteration */
for (;;)
{
notifyInterruptEnabled = 1;
if (!notifyInterruptOccurred)
break;
notifyInterruptEnabled = 0;
if (notifyInterruptOccurred)
{
/* Here, it is finally safe to do stuff. */
if (Trace_notify)
elog(DEBUG1, "HandleNotifyInterrupt: perform async notify");
ProcessIncomingNotify();
if (Trace_notify)
elog(DEBUG1, "HandleNotifyInterrupt: done");
}
}
/*
* Restore ImmediateInterruptOK, and check for interrupts if needed.
*/
ImmediateInterruptOK = save_ImmediateInterruptOK;
if (save_ImmediateInterruptOK)
CHECK_FOR_INTERRUPTS();
}
else
{
/*
* In this path it is NOT SAFE to do much of anything, except this:
*/
notifyInterruptOccurred = 1;
}
}
| static bool IsListeningOn | ( | const char * | channel | ) | [static] |
Definition at line 1125 of file async.c.
References lfirst.
Referenced by asyncQueueProcessPageEntries(), and Exec_ListenCommit().
{
ListCell *p;
foreach(p, listenChannels)
{
char *lchan = (char *) lfirst(p);
if (strcmp(lchan, channel) == 0)
return true;
}
return false;
}
| static void NotifyMyFrontEnd | ( | const char * | channel, | |
| const char * | payload, | |||
| int32 | srcPid | |||
| ) | [static] |
Definition at line 2125 of file async.c.
References buf, DestRemote, elog, FrontendProtocol, INFO, PG_PROTOCOL_MAJOR, pq_beginmessage(), pq_endmessage(), pq_sendint(), pq_sendstring(), and whereToSendOutput.
Referenced by asyncQueueProcessPageEntries().
{
if (whereToSendOutput == DestRemote)
{
StringInfoData buf;
pq_beginmessage(&buf, 'A');
pq_sendint(&buf, srcPid, sizeof(int32));
pq_sendstring(&buf, channel);
if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
pq_sendstring(&buf, payload);
pq_endmessage(&buf);
/*
* NOTE: we do not do pq_flush() here. For a self-notify, it will
* happen at the end of the transaction, and for incoming notifies
* ProcessIncomingNotify will do it after finding all the notifies.
*/
}
else
elog(INFO, "NOTIFY for \"%s\" payload \"%s\"", channel, payload);
}
| Datum pg_listening_channels | ( | PG_FUNCTION_ARGS | ) |
Definition at line 677 of file async.c.
References CStringGetTextDatum, lfirst, list_head(), lnext, MemoryContextSwitchTo(), FuncCallContext::multi_call_memory_ctx, NULL, palloc(), SRF_FIRSTCALL_INIT, SRF_IS_FIRSTCALL, SRF_PERCALL_SETUP, SRF_RETURN_DONE, SRF_RETURN_NEXT, and FuncCallContext::user_fctx.
{
FuncCallContext *funcctx;
ListCell **lcp;
/* stuff done only on the first call of the function */
if (SRF_IS_FIRSTCALL())
{
MemoryContext oldcontext;
/* create a function context for cross-call persistence */
funcctx = SRF_FIRSTCALL_INIT();
/* switch to memory context appropriate for multiple function calls */
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
/* allocate memory for user context */
lcp = (ListCell **) palloc(sizeof(ListCell *));
*lcp = list_head(listenChannels);
funcctx->user_fctx = (void *) lcp;
MemoryContextSwitchTo(oldcontext);
}
/* stuff done on every call of the function */
funcctx = SRF_PERCALL_SETUP();
lcp = (ListCell **) funcctx->user_fctx;
while (*lcp != NULL)
{
char *channel = (char *) lfirst(*lcp);
*lcp = lnext(*lcp);
SRF_RETURN_NEXT(funcctx, CStringGetTextDatum(channel));
}
SRF_RETURN_DONE(funcctx);
}
| Datum pg_notify | ( | PG_FUNCTION_ARGS | ) |
Definition at line 500 of file async.c.
References Async_Notify(), PG_ARGISNULL, PG_GETARG_TEXT_PP, PG_RETURN_VOID, PreventCommandDuringRecovery(), and text_to_cstring().
{
const char *channel;
const char *payload;
if (PG_ARGISNULL(0))
channel = "";
else
channel = text_to_cstring(PG_GETARG_TEXT_PP(0));
if (PG_ARGISNULL(1))
payload = "";
else
payload = text_to_cstring(PG_GETARG_TEXT_PP(1));
/* For NOTIFY as a statement, this is checked in ProcessUtility */
PreventCommandDuringRecovery("NOTIFY");
Async_Notify(channel, payload);
PG_RETURN_VOID();
}
| void PreCommit_Notify | ( | void | ) |
Definition at line 762 of file async.c.
References AccessExclusiveLock, ListenAction::action, asyncQueueAddEntries(), asyncQueueFillWarning(), asyncQueueIsFull(), AsyncQueueLock, backendHasSentNotifications, DatabaseRelationId, DEBUG1, elog, ereport, errcode(), errmsg(), ERROR, Exec_ListenPreCommit(), GetCurrentTransactionId(), InvalidOid, lfirst, list_head(), LISTEN_LISTEN, LISTEN_UNLISTEN, LISTEN_UNLISTEN_ALL, LockSharedObject(), LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), NIL, NULL, and Trace_notify.
Referenced by CommitTransaction().
{
ListCell *p;
if (pendingActions == NIL && pendingNotifies == NIL)
return; /* no relevant statements in this xact */
if (Trace_notify)
elog(DEBUG1, "PreCommit_Notify");
/* Preflight for any pending listen/unlisten actions */
foreach(p, pendingActions)
{
ListenAction *actrec = (ListenAction *) lfirst(p);
switch (actrec->action)
{
case LISTEN_LISTEN:
Exec_ListenPreCommit();
break;
case LISTEN_UNLISTEN:
/* there is no Exec_UnlistenPreCommit() */
break;
case LISTEN_UNLISTEN_ALL:
/* there is no Exec_UnlistenAllPreCommit() */
break;
}
}
/* Queue any pending notifies */
if (pendingNotifies)
{
ListCell *nextNotify;
/*
* Make sure that we have an XID assigned to the current transaction.
* GetCurrentTransactionId is cheap if we already have an XID, but not
* so cheap if we don't, and we'd prefer not to do that work while
* holding AsyncQueueLock.
*/
(void) GetCurrentTransactionId();
/*
* Serialize writers by acquiring a special lock that we hold till
* after commit. This ensures that queue entries appear in commit
* order, and in particular that there are never uncommitted queue
* entries ahead of committed ones, so an uncommitted transaction
* can't block delivery of deliverable notifications.
*
* We use a heavyweight lock so that it'll automatically be released
* after either commit or abort. This also allows deadlocks to be
* detected, though really a deadlock shouldn't be possible here.
*
* The lock is on "database 0", which is pretty ugly but it doesn't
* seem worth inventing a special locktag category just for this.
* (Historical note: before PG 9.0, a similar lock on "database 0" was
* used by the flatfiles mechanism.)
*/
LockSharedObject(DatabaseRelationId, InvalidOid, 0,
AccessExclusiveLock);
/* Now push the notifications into the queue */
backendHasSentNotifications = true;
nextNotify = list_head(pendingNotifies);
while (nextNotify != NULL)
{
/*
* Add the pending notifications to the queue. We acquire and
* release AsyncQueueLock once per page, which might be overkill
* but it does allow readers to get in while we're doing this.
*
* A full queue is very uncommon and should really not happen,
* given that we have so much space available in the SLRU pages.
* Nevertheless we need to deal with this possibility. Note that
* when we get here we are in the process of committing our
* transaction, but we have not yet committed to clog, so at this
* point in time we can still roll the transaction back.
*/
LWLockAcquire(AsyncQueueLock, LW_EXCLUSIVE);
asyncQueueFillWarning();
if (asyncQueueIsFull())
ereport(ERROR,
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
errmsg("too many notifications in the NOTIFY queue")));
nextNotify = asyncQueueAddEntries(nextNotify);
LWLockRelease(AsyncQueueLock);
}
}
}
| void ProcessCompletedNotifies | ( | void | ) |
Definition at line 1057 of file async.c.
References asyncQueueAdvanceTail(), asyncQueueReadAllNotifications(), backendHasSentNotifications, CommitTransactionCommand(), CurrentMemoryContext, DEBUG1, elog, MemoryContextSwitchTo(), NIL, SignalBackends(), StartTransactionCommand(), and Trace_notify.
Referenced by PostgresMain().
{
MemoryContext caller_context;
bool signalled;
/* Nothing to do if we didn't send any notifications */
if (!backendHasSentNotifications)
return;
/*
* We reset the flag immediately; otherwise, if any sort of error occurs
* below, we'd be locked up in an infinite loop, because control will come
* right back here after error cleanup.
*/
backendHasSentNotifications = false;
/*
* We must preserve the caller's memory context (probably MessageContext)
* across the transaction we do here.
*/
caller_context = CurrentMemoryContext;
if (Trace_notify)
elog(DEBUG1, "ProcessCompletedNotifies");
/*
* We must run asyncQueueReadAllNotifications inside a transaction, else
* bad things happen if it gets an error.
*/
StartTransactionCommand();
/* Send signals to other backends */
signalled = SignalBackends();
if (listenChannels != NIL)
{
/* Read the queue ourselves, and send relevant stuff to the frontend */
asyncQueueReadAllNotifications();
}
else if (!signalled)
{
/*
* If we found no other listening backends, and we aren't listening
* ourselves, then we must execute asyncQueueAdvanceTail to flush the
* queue, because ain't nobody else gonna do it. This prevents queue
* overflow when we're sending useless notifies to nobody. (A new
* listener could have joined since we looked, but if so this is
* harmless.)
*/
asyncQueueAdvanceTail();
}
CommitTransactionCommand();
MemoryContextSwitchTo(caller_context);
/* We don't need pq_flush() here since postgres.c will do one shortly */
}
| static void ProcessIncomingNotify | ( | void | ) | [static] |
Definition at line 2078 of file async.c.
References asyncQueueReadAllNotifications(), CommitTransactionCommand(), DEBUG1, DisableCatchupInterrupt(), elog, EnableCatchupInterrupt(), NIL, notifyInterruptOccurred, pq_flush(), set_ps_display(), StartTransactionCommand(), and Trace_notify.
Referenced by EnableNotifyInterrupt(), and HandleNotifyInterrupt().
{
bool catchup_enabled;
/* We *must* reset the flag */
notifyInterruptOccurred = 0;
/* Do nothing else if we aren't actively listening */
if (listenChannels == NIL)
return;
/* Must prevent catchup interrupt while I am running */
catchup_enabled = DisableCatchupInterrupt();
if (Trace_notify)
elog(DEBUG1, "ProcessIncomingNotify");
set_ps_display("notify interrupt", false);
/*
* We must run asyncQueueReadAllNotifications inside a transaction, else
* bad things happen if it gets an error.
*/
StartTransactionCommand();
asyncQueueReadAllNotifications();
CommitTransactionCommand();
/*
* Must flush the notify messages to ensure frontend gets them promptly.
*/
pq_flush();
set_ps_display("idle", false);
if (Trace_notify)
elog(DEBUG1, "ProcessIncomingNotify: done");
if (catchup_enabled)
EnableCatchupInterrupt();
}
| static void queue_listen | ( | ListenActionKind | action, | |
| const char * | channel | |||
| ) | [static] |
Definition at line 596 of file async.c.
References ListenAction::action, ListenAction::channel, CurTransactionContext, lappend(), MemoryContextSwitchTo(), and palloc().
Referenced by Async_Listen(), Async_Unlisten(), and Async_UnlistenAll().
{
MemoryContext oldcontext;
ListenAction *actrec;
/*
* Unlike Async_Notify, we don't try to collapse out duplicates. It would
* be too complicated to ensure we get the right interactions of
* conflicting LISTEN/UNLISTEN/UNLISTEN_ALL, and it's unlikely that there
* would be any performance benefit anyway in sane applications.
*/
oldcontext = MemoryContextSwitchTo(CurTransactionContext);
/* space for terminating null is included in sizeof(ListenAction) */
actrec = (ListenAction *) palloc(sizeof(ListenAction) + strlen(channel));
actrec->action = action;
strcpy(actrec->channel, channel);
pendingActions = lappend(pendingActions, actrec);
MemoryContextSwitchTo(oldcontext);
}
| static bool SignalBackends | ( | void | ) | [static] |
Definition at line 1445 of file async.c.
References AsyncQueueLock, DEBUG3, elog, i, InvalidPid, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MaxBackends, MyProcPid, palloc(), pfree(), PROCSIG_NOTIFY_INTERRUPT, QUEUE_BACKEND_PID, QUEUE_BACKEND_POS, QUEUE_HEAD, QUEUE_POS_EQUAL, and SendProcSignal().
Referenced by ProcessCompletedNotifies().
{
bool signalled = false;
int32 *pids;
BackendId *ids;
int count;
int i;
int32 pid;
/*
* Identify all backends that are listening and not already up-to-date. We
* don't want to send signals while holding the AsyncQueueLock, so we just
* build a list of target PIDs.
*
* XXX in principle these pallocs could fail, which would be bad. Maybe
* preallocate the arrays? But in practice this is only run in trivial
* transactions, so there should surely be space available.
*/
pids = (int32 *) palloc(MaxBackends * sizeof(int32));
ids = (BackendId *) palloc(MaxBackends * sizeof(BackendId));
count = 0;
LWLockAcquire(AsyncQueueLock, LW_EXCLUSIVE);
for (i = 1; i <= MaxBackends; i++)
{
pid = QUEUE_BACKEND_PID(i);
if (pid != InvalidPid && pid != MyProcPid)
{
QueuePosition pos = QUEUE_BACKEND_POS(i);
if (!QUEUE_POS_EQUAL(pos, QUEUE_HEAD))
{
pids[count] = pid;
ids[count] = i;
count++;
}
}
}
LWLockRelease(AsyncQueueLock);
/* Now send signals */
for (i = 0; i < count; i++)
{
pid = pids[i];
/*
* Note: assuming things aren't broken, a signal failure here could
* only occur if the target backend exited since we released
* AsyncQueueLock; which is unlikely but certainly possible. So we
* just log a low-level debug message if it happens.
*/
if (SendProcSignal(pid, PROCSIG_NOTIFY_INTERRUPT, ids[i]) < 0)
elog(DEBUG3, "could not signal backend with PID %d: %m", pid);
else
signalled = true;
}
pfree(pids);
pfree(ids);
return signalled;
}
bool amRegisteredListener = false [static] |
Definition at line 354 of file async.c.
Referenced by asyncQueueUnregister(), AtAbort_Notify(), AtCommit_Notify(), and Exec_ListenPreCommit().
SlruCtlData AsyncCtlData [static] |
AsyncQueueControl* asyncQueueControl [static] |
bool backendHasSentNotifications = false [static] |
Definition at line 357 of file async.c.
Referenced by PreCommit_Notify(), and ProcessCompletedNotifies().
List* listenChannels = NIL [static] |
volatile sig_atomic_t notifyInterruptEnabled = 0 [static] |
Definition at line 347 of file async.c.
Referenced by DisableNotifyInterrupt(), EnableNotifyInterrupt(), and HandleNotifyInterrupt().
volatile sig_atomic_t notifyInterruptOccurred = 0 [static] |
Definition at line 348 of file async.c.
Referenced by EnableNotifyInterrupt(), HandleNotifyInterrupt(), and ProcessIncomingNotify().
List* pendingActions = NIL [static] |
List* pendingNotifies = NIL [static] |
| bool Trace_notify = false |
Definition at line 360 of file async.c.
Referenced by Async_Listen(), Async_Notify(), Async_Unlisten(), Async_UnlistenAll(), AtCommit_Notify(), EnableNotifyInterrupt(), Exec_ListenPreCommit(), Exec_UnlistenAllCommit(), Exec_UnlistenCommit(), HandleNotifyInterrupt(), PreCommit_Notify(), ProcessCompletedNotifies(), and ProcessIncomingNotify().
bool unlistenExitRegistered = false [static] |
Definition at line 351 of file async.c.
Referenced by Async_Unlisten(), Async_UnlistenAll(), and Exec_ListenPreCommit().
List* upperPendingActions = NIL [static] |
List* upperPendingNotifies = NIL [static] |
1.7.1