Chapter 4 omniORB configuration and API
omniORB 4.1 has a wide range of parameters that can be
configured. They can be set in the configuration file / Windows
registry, as environment variables, on the command line, or within a
proprietary extra argument to CORBA::ORB_init(). A few parameters
can be configured at run time. This chapter lists all the
configuration parameters, and how they are used.
4.1 Setting parameters
When CORBA::ORB_init() is called, the value for each configuration
parameter is searched for in the following order:
- Command line arguments
- ORB_init() options
- Environment variables
- Configuration file / Windows registry
- Built-in defaults
4.1.1 Command line arguments
Command line arguments take the form
`-ORBparameter', and usually expect another
argument. An example is `-ORBtraceLevel 10'.
4.1.2 ORB_init() parameter
ORB_init()'s extra argument accepts an array of two-dimensional
string arrays, like this:
const char* options[][2] = { { "traceLevel", "1" }, { 0, 0 } };
orb = CORBA::ORB_init(argc,argv,"omniORB4",options);
4.1.3 Environment variables
Environment variables consist of the parameter name prefixed with
`ORB'. Using bash, for example
export ORBtraceLevel=10
4.1.4 Configuration file
The best way to understand the format of the configuration file is to
look at the sample.cfg file in the omniORB distribution. Each
parameter is set on a single line like
traceLevel = 10
Some parameters can have more than one value, in which case the
parameter name may be specified more than once, or you can leave it
out:
InitRef = NameService=corbaname::host1.example.com
= InterfaceRepository=corbaloc::host2.example.com:1234/IfR
-
Note how command line arguments and environment variables prefix
parameter names with `-ORB' and `ORB' respectively, but the
configuration file and the extra argument to ORB_init() do not use
a prefix.
4.1.5 Windows registry
On Windows, configuration parameters can be stored in the registry,
under the key HKEY_LOCAL_MACHINE\SOFTWARE\omniORB.
The file sample.reg shows the settings that can be made. It can
be edited and then imported into regedit.
4.2 Tracing options
The following options control debugging trace output.
traceLevel default =
1
omniORB can output tracing and diagnostic messages to the standard
error stream. The following levels are defined:
| |
| level 0 |
critical errors only |
| level 1 |
informational messages only |
| level 2 |
configuration information and warnings |
| level 5 |
notifications when server threads are
created and communication endpoints are shutdown |
| level 10 |
execution and exception traces |
| level 25 |
trace each send or receive of a giop message |
| level 30 |
dump up to 128 bytes of each giop message |
| level 40 |
dump complete contents of each giop message |
The trace level is cumulative, so at level 40, all trace
messages are output.
traceExceptions default =
0
If the traceExceptions parameter is set true, all system
exceptions are logged as they are thrown, along with details about
where the exception is thrown from. This parameter is enabled by
default if the traceLevel is set to 10 or more.
traceInvocations default =
0
If the traceInvocations parameter is set true, all local and
remote invocations are logged, in addition to any logging that may
have been selected with traceLevel.
traceInvocationReturns default =
0
If the traceInvocationReturns parameter is set true, a log
message is output as an operation invocation returns. In conjunction
with traceInvocations and traceTime (described below),
this provides a simple way of timing CORBA calls within your
application.
traceThreadId default =
0
If traceThreadId is set true, all trace messages are prefixed
with the id of the thread outputting the message. This can be handy
for tracking down race conditions, but it adds significant overhead to
the logging function so it is turned off by default.
traceTime default =
0
If traceTime is set true, all trace messages are prefixed with
the time. This is useful, but on some platforms it adds a very large
overhead, so it is turned off by default.
4.2.1 Tracing API
The tracing parameters can be modified at runtime by assigning to the
following variables
namespace omniORB {
CORBA::ULong traceLevel;
CORBA::Boolean traceExceptions;
CORBA::Boolean traceInvocations;
CORBA::Boolean traceInvocationReturns;
CORBA::Boolean traceThreadId;
CORBA::Boolean traceTime;
};
Log messages can be sent somewhere other than stderr by registering a
logging function which is called with the text of each log message:
namespace omniORB {
typedef void (*logFunction)(const char*);
void setLogFunction(logFunction f);
};
The log function must not make any CORBA calls, since that could lead
to infinite recursion as outputting a log message caused other log
messages to be generated, and so on.
4.3 Miscellaneous global options
These options control miscellaneous features that affect the whole ORB
runtime.
dumpConfiguration default =
0
If set true, the ORB dumps the values of all configuration parameters
at start-up.
scanGranularity default =
5
As explained in chapter 8, omniORB regularly
scans incoming and outgoing connections, so it can close unused
ones. This value is the granularity in seconds at which the ORB
performs its scans. A value of zero turns off the scanning altogether.
nativeCharCodeSet default =
ISO-8859-1
The native code set the application is using for char and
string. See chapter 9.
nativeWCharCodeSet default =
UTF-16
The native code set the application is using for wchar and
wstring. See chapter 9.
copyValuesInLocalCalls default =
1
Determines whether valuetype parameters in local calls are copied or
not. See chapter 13.
abortOnInternalError default =
0
If this is set true, internal fatal errors will abort immediately,
rather than throwing the omniORB::fatalException exception.
This can be helpful for tracking down bugs, since it leaves the call
stack intact.
4.4 Client side options
These options control aspects of client-side behaviour.
InitRef default =
none
Specify objects available from
ORB::resolve_initial_references(). The arguments take the form
<key>=<uri>, where key is the name given to
resolve_initial_references() and uri is a
valid CORBA object reference URI, as detailed in
chapter 6.
DefaultInitRef default =
none
Specify the default URI prefix for
resolve_initial_references(), as explained in
chapter 6.
clientTransportRule default =
* unix,tcp,ssl
Used to specify the way the client contacts a server, depending on the
server's address. See section 8.7.1 for details.
clientCallTimeOutPeriod default =
0
Call timeout in milliseconds for the client side. If a call takes
longer than the specified number of milliseconds, the ORB closes the
connection to the server and raises a TRANSIENT exception. A
value of zero means no timeout; calls can block for ever. See
section 8.3.1 for more information about timeouts.
Note: omniORB 3 had timeouts specified in seconds;
omniORB 4.0 and later use milliseconds for timeouts.
clientConnectTimeOutPeriod default =
0
The timeout that is used in the case that a new network connection is
established to the server. A value of zero means that the normal call
timeout is used. See section 8.3.1 for more information
about timeouts.
supportPerThreadTimeOut default =
0
If this parameter is set true, timeouts can be set on a per thread
basis, as well as globally and per object. Checking per-thread storage
has a noticeable performance impact, so it is turned off by default.
outConScanPeriod default =
120
Idle timeout in seconds for outgoing (i.e. client initiated)
connections. If a connection has been idle for this amount of time,
the ORB closes it. See section 8.5.
maxGIOPConnectionPerServer default =
5
The maximum number of concurrent connections the ORB will open to a
single server. If multiple threads on the client call the same
server, the ORB opens additional connections to the server, up to the
maximum specified by this parameter. If the maximum is reached,
threads are blocked until a connection becomes free for them to use.
oneCallPerConnection default =
1
When this parameter is set to true (the default), the ORB will only
send a single call on a connection at a time. If multiple client
threads invoke on the same server, multiple connections are opened, up
to the limit specified by
maxGIOPConnectionPerServer. With this parameter set to
false, the ORB will allow concurrent calls on a single
connection. This saves connection resources, but requires slightly
more management work for both client and server. Some server-side ORBs
(including omniORB versions before 4.0) serialise all calls on a
single connection.
offerBiDirectionalGIOP default =
0
If set true, the client will indicate to servers that it is willing to
accept callbacks on client-initiated connections using bidirectional
GIOP, provided the relevant POA policies are set. See
section 8.8.
diiThrowsSysExceptions default =
0
If this is true, DII functions throw system exceptions; if it is
false, system exceptions that occur are passed through the
Environment object.
verifyObjectExistsAndType default =
1
By default, omniORB uses the GIOP LOCATE_REQUEST message to
verify the existence of an object prior to the first invocation. In
the case that the full type of the object is not known, it instead
calls the _is_a() operation to check the object's type. Some ORBs
have bugs that mean one or other of these operations fail. Setting
this parameter false prevents omniORB from making these calls.
giopTargetAddressMode default =
0
GIOP 1.2 supports three addressing modes for contacting objects. This
parameter selects the mode that omniORB uses. A value of 0 means
GIOP::KeyAddr; 1 means GIOP::ProfileAddr; 2 means
GIOP::ReferenceAddr.
bootstrapAgentHostname default =
none
If set, this parameter indicates the hostname to use for look-ups
using the obsolete Sun bootstrap agent. This mechanism is superseded
by the interoperable naming service.
bootstrapAgentPort default =
900
The port number for the obsolete Sun bootstrap agent.
principal default =
none
GIOP 1.0 and 1.1 have a request header field named `principal', which
contains a sequence of octets. It was never defined what it should
mean, and its use is now deprecated; GIOP 1.2 has no such field. Some
systems (e.g. Gnome) use the principal field as a primitive
authentication scheme. This parameter sets the data omniORB uses in
the principal field. The default is an empty sequence.
4.5 Server side options
These parameters affect server-side operations.
endPoint default = giop:tcp::
endPointNoListen
endPointPublish
endPointNoPublish
endPointPublishAllIFs
These options determine the end-points the ORB should listen on, and
the details that should be published in IORs. See
chapter 8 for details.
serverTransportRule default =
* unix,tcp,ssl
Configure the rules about whether a server should accept an incoming
connection from a client. See section 8.7.2 for
details.
serverCallTimeOutPeriod default =
0
This timeout is used to catch the situation that the server starts
receiving a request, but the end of the request never comes. If a
calls takes longer than the specified number of milliseconds to
arrive, the ORB shuts the connection. A value of zero means never
timeout.
inConScanPeriod default =
180
Idle timeout in seconds for incoming. If a connection has been idle
for this amount of time, the ORB closes it. See
section 8.5.
threadPerConnectionPolicy default =
1
If true (the default), the ORB dedicates one server thread to each
incoming connection. Setting it false means the server should use a
thread pool.
maxServerThreadPerConnection default =
100
If the client multiplexes several concurrent requests on a single
connection, omniORB uses extra threads to service them. This parameter
specifies the maximum number of threads that are allowed to service a
single connection at any one time.
maxServerThreadPoolSize default =
100
The maximum number of threads the server will allocate to do various
tasks, including dispatching calls in the thread pool mode. This
number does not include threads dispatched under the thread per
connection server mode.
threadPerConnectionUpperLimit default =
10000
If the threadPerConnectionPolicy parameter is true, the ORB can
automatically transition to thread pool mode if too many connections
arrive. This parameter sets the number of connections at which thread
pooling is started. The default of 10000 is designed to mean that it
never happens.
threadPerConnectionLowerLimit default =
9000
If thread pooling was started because the number of connections hit
the upper limit, this parameter determines when thread per connection
should start again.
threadPoolWatchConnection default =
1
If non-zero, threads from the pool temporarily behave a bit like
thread per connection after dispatching a call. See
section 8.4.2 for details.
acceptBiDirectionalGIOP default =
0
Determines whether a server will ever accept clients' offers of
bidirectional GIOP connections. See section 8.8.
unixTransportDirectory default =
/tmp/omni-%u
(Unix platforms only). Selects the location used to store Unix domain
sockets. The `%u' is expanded to the user name.
unixTransportPermission default =
0777
(Unix platforms only). Determines the octal permission bits for Unix
domain sockets. By default, all users can connect to a server, just as
with TCP.
supportCurrent default =
1
omniORB supports the PortableServer::Current interface to
provide thread context information to servants. Supporting current has
a small but noticeable run-time overhead due to accessing thread
specific storage, so this option allows it to be turned off.
objectTableSize default =
0
Hash table size of the Active Object Map. If this is zero, the ORB
uses a dynamically resized open hash table. This is normally the best
option, but it leads to less predictable performance since any
operation which adds or removes a table entry may trigger a resize. If
set to a non-zero value, the hash table has the specified number of
entries, and is never resized. Note that the hash table is open, so
this does not limit the number of active objects, just how efficiently
they can be located.
poaHoldRequestTimeout default =
0
If a POA is put in the HOLDING state, calls to it will be timed
out after the specified number of milliseconds, by raising a
TRANSIENT exception. Zero means no timeout.
supportBootstrapAgent default =
0
If set true, servers support the Sun bootstrap agent protocol.
4.5.1 Main thread selection
There is one server-side parameter that must be set with an API
function, rather than a normal configuration parameter:
namespace omniORB {
void setMainThread();
};
POAs with the MAIN_THREAD policy dispatch calls on the `main'
thread. By default, omniORB assumes that the thread that initialised
the omnithread library is the `main' thread. To choose a different
thread, call this function from the desired `main' thread. The calling
thread must have an omni_thread associated with it (i.e. it
must have been created by omnithread, or
omni_thread::create_dummy() must have been called). If it
does not, the function throws CORBA::INITIALIZE.
Note that calls are only actually dispatched to the `main' thread if
ORB::run() or ORB::perform_work() is called from that thread.
4.6 GIOP and interoperability options
These options control omniORB's use of GIOP, and cover some areas
where omniORB can work around buggy behaviour by other ORBs.
maxGIOPVerson default =
1.2
Choose the maximum GIOP version the ORB should support. Valid values
are 1.0, 1.1 and 1.2.
giopMaxMsgSize default =
2097152
The largest message, in bytes, that the ORB will send or receive, to
avoid resource starvation. If the limit is exceeded, a MARSHAL
exception is thrown. The size must be >= 8192.
strictIIOP default =
1
If true, be strict about interpretation of the IIOP specification; if
false, permit some buggy behaviour to pass.
lcdMode default =
0
If true, select `Lowest Common Denominator' mode. This disables
various IIOP and GIOP features that are known to cause problems with
some ORBs.
tcAliasExpand default =
0
This flag is used to indicate whether TypeCodes associated with Anys
should have aliases removed. This functionality is included because
some ORBs will not recognise an Any containing a TypeCode with aliases
to be the same as the actual type contained in the Any. Note that
omniORB will always remove top-level aliases, but will not remove
aliases from TypeCodes that are members of other TypeCodes (e.g.
TypeCodes for members of structs etc.), unless tcAliasExpand is
set to 1. There is a performance penalty when inserting into an Any if
tcAliasExpand is set to 1.
useTypeCodeIndirections default =
1
TypeCode Indirections reduce the size of marshalled TypeCodes, and are
essential for recursive types, but some old ORBs do not support them.
Setting this flag to false prevents the use of indirections (and,
therefore, recursive TypeCodes).
acceptMisalignedTcIndirections default =
0
If true, try to fix a mis-aligned indirection in a typecode. This is
used to work around a bug in some old versions of Visibroker's Java
ORB.
4.7 System Exception Handlers
By default, all system exceptions that are raised during an operation
invocation, with the exception of some cases of
CORBA::TRANSIENT, are propagated to the application code. Some
applications may prefer to trap these exceptions within the proxy
objects so that the application logic does not have to deal with the
error condition. For example, when a CORBA::COMM_FAILURE is
received, an application may just want to retry the invocation until
it finally succeeds. This approach is useful for objects that are
persistent and have idempotent operations.
omniORB provides a set of functions to install exception handlers.
Once they are installed, proxy objects will call these handlers when
the associated system exceptions are raised by the ORB runtime.
Handlers can be installed for CORBA::TRANSIENT,
CORBA::COMM_FAILURE and CORBA::SystemException. This
last handler covers all system exceptions other than the two covered
by the first two handlers. An exception handler can be installed for
individual proxy objects, or it can be installed for all proxy objects
in the address space.
4.7.1 Minor codes
omniORB makes extensive use of exception minor codes to indicate the
specific circumstances surrounding a system exception. The file
include/omniORB4/minorCode.h contains definitions of all the
minor codes used in omniORB, covering codes allocated in the CORBA
specification, and ones specific to omniORB. In compilers with
namespace support, the minor code constants appear in namespace
omni; otherwise they are in the global scope.
Applications can use minor codes to adjust their behaviour according
to the condition, e.g.
try {
...
}
catch (CORBA::TRANSIENT& ex) {
if (ex.minor() == omni::TRANSIENT_ConnectFailed) {
// retry with a different object reference...
}
else {
// print an error message...
}
}
4.7.2 CORBA::TRANSIENT handlers
TRANSIENT exceptions can occur in many circumstances. One
circumstance is as follows:
- The client invokes on an object reference.
- The object replies with a LOCATION_FORWARD message.
- The client caches the new location and retries to the new location.
- Time passes...
- The client tries to invoke on the object again, using the
cached, forwarded location.
- The attempt to contact the object fails.
- The ORB runtime resets the location cache and throws a
TRANSIENT exception with minor code
TRANSIENT_FailedOnForwarded.
In this situation, the default TRANSIENT exception handler
retries the call, using the object's original location. If the retry
results in another LOCATION_FORWARD, to the same or a
different location, and that forwarded location fails
immediately, the TRANSIENT exception will occur again, and the
pattern will repeat. With repeated exceptions, the handler starts
adding delays before retries, with exponential back-off.
In all other circumstances, the default TRANSIENT handler just
passes the exception on to the caller.
Applications can override the default behaviour by installing their
own exception handler. The API to do so is summarised below:
namespace omniORB {
typedef CORBA::Boolean
(*transientExceptionHandler_t)(void* cookie,
CORBA::ULong n_retries,
const CORBA::TRANSIENT& ex);
void
installTransientExceptionHandler(void* cookie,
transientExceptionHandler_t fn);
void
installTransientExceptionHandler(CORBA::Object_ptr obj,
void* cookie,
transientExceptionHandler_t fn);
}
The overloaded function installTransientExceptionHandler() can be
used to install the exception handlers for CORBA::TRANSIENT.
Two forms are available: the first form installs an exception handler
for all object references except for those which have an exception
handler installed by the second form, which takes an additional
argument to identify the target object reference. The argument
cookie is an opaque pointer which will be passed on by the ORB
when it calls the exception handler.
An exception handler will be called by proxy objects with three
arguments. The cookie is the opaque pointer registered by
installTransientExceptionHandler(). The argument
n_retries is the number of times the proxy has called this
handler for the same invocation. The argument ex is the value
of the exception caught. The exception handler is expected to do
whatever is appropriate and return a boolean value. If the return
value is TRUE(1), the proxy object retries the operation. If the
return value is FALSE(0), the original exception is propagated into
the application code. In the case of a TRANSIENT exception due
to a failed location forward, the exception propagated to the
application is the original exception that caused the
TRANSIENT (e.g. a COMM_FAILURE or
OBJECT_NOT_EXIST), rather than the TRANSIENT
exception1.
The following sample code installs a simple exception handler for all
objects and for a specific object:
CORBA::Boolean my_transient_handler1 (void* cookie,
CORBA::ULong retries,
const CORBA::TRANSIENT& ex)
{
cerr << "transient handler 1 called." << endl;
return 1; // retry immediately.
}
CORBA::Boolean my_transient_handler2 (void* cookie,
CORBA::ULong retries,
const CORBA::TRANSIENT& ex)
{
cerr << "transient handler 2 called." << endl;
return 1; // retry immediately.
}
static Echo_ptr myobj;
void installhandlers()
{
omniORB::installTransientExceptionHandler(0,my_transient_handler1);
// All proxy objects will call my_transient_handler1 from now on.
omniORB::installTransientExceptionHandler(myobj,0,my_transient_handler2);
// The proxy object of myobj will call my_transient_handler2 from now on.
}
4.7.3 CORBA::COMM_FAILURE
If the ORB has successfully contacted an object at some point, and
access to it subsequently fails (and the condition for
TRANSIENT described above does not occur), the ORB raises a
CORBA::COMM_FAILURE exception.
The default behaviour of the proxy objects is to propagate this
exception to the application. Applications can override the default
behaviour by installing their own exception handlers. The API to do so
is summarised below:
typedef CORBA::Boolean
(*commFailureExceptionHandler_t)(void* cookie,
CORBA::ULong n_retries,
const CORBA::COMM_FAILURE& ex);
void
installCommFailureExceptionHandler(void* cookie,
commFailureExceptionHandler_t fn);
void
installCommFailureExceptionHandler(CORBA::Object_ptr obj,
void* cookie,
commFailureExceptionHandler_t fn);
The functions are equivalent to their counterparts for
CORBA::TRANSIENT.
4.7.4 CORBA::SystemException
If a system exceptions other than TRANSIENT or
COMM_FAILURE occurs, the default behaviour of the proxy
objects is to propagate this exception to the application.
Applications can override the default behaviour by installing their
own exception handlers. The API to do so is summarised below:
typedef CORBA::Boolean
(*systemExceptionHandler_t)(void* cookie,
CORBA::ULong n_retries,
const CORBA::SystemException& ex);
void
installSystemExceptionHandler(void* cookie,
systemExceptionHandler_t fn);
void
installSystemExceptionHandler(CORBA::Object_ptr obj,
void* cookie,
systemExceptionHandler_t fn);
The functions are equivalent to their counterparts for
CORBA::TRANSIENT.
4.8 Location forwarding
Any CORBA operation invocation can return a LOCATION_FORWARD
message to the caller, indicating that it should retry the invocation
on a new object reference. The standard allows ServantManagers to
trigger LOCATION_FORWARDs by raising the
PortableServer::ForwardRequest exception, but it does not
provide a similar mechanism for normal servants. omniORB provides the
omniORB::LOCATION_FORWARD exception for this purpose. It
can be thrown by any operation implementation.
namespace omniORB {
class LOCATION_FORWARD {
public:
LOCATION_FORWARD(CORBA::Object_ptr objref);
};
};
The exception object consumes the object reference it is
passed.
- 1
- This is a change from omniORB 4.0 and earlier,
where it was the TRANSIENT exception that was propagated to the
application.