Frequently asked questions

What clients do I use with Couchbase?

Couchbase Server is compatible with existing memcached clients. If a memcached client already exists, just point it at couchbase. Regular testing is done with spymemcached (Java client), libmemcached, and fauna (Ruby client).

What is a vBucket?

A vBucket is conceptually a computed subset of all possible mapping keys. vBuckets are mapped to servers statically and have a consistent key through vBucket computations. The number of vBuckets in a cluster remains constant regardless of server topology which means that a key always maps to the same vBucket given the same hash.

What is a TAP stream?

A TAP stream is a when a client requests a stream of item updates from the server. That is, as other clients are requesting item mutations (for example, SET's and DELETE's), a TAP stream client can "wire-tap" the server to receive a stream of item change notifications. When a TAP stream client starts its connection, it may also optionally request a stream of all items stored in the server, even if no other clients are making any item changes. On the TAP stream connection setup options, a TAP stream client may request to receive just current items stored in the server (all items until "now"), or all item changes from now onward into in the future, or both.

Which ports does Couchbase Server need?

See the Network ports section for up to date information.

What hardware and platforms does Couchbase Server support?

See the Supported platforms section for up to date information.

How can I get Couchbase on a different OS?

The Couchbase source code is quite portable and is known to have been built on several other UNIX and Linux based OSs.

Can I query Couchbase by something other than the key name?

Not directly. It's possible to build these kinds of solutions atop TAP. For instance, it is possible to stream out the data, process it with Cascading, then create indexes in Elasticsearch.

What is the maximum item size in Couchbase>

The default item size for Couchbase buckets is 20 MBytes. The default item size for memcached buckets is 1 MByte.

How do I the change password?

With the command-line tool (CLI), use couchbase-cli cluster-init:

couchbase-cli cluster-init -c cluster_IP:8091
  -u current_username-p current password
  --cluster-init-username=new_username
  --cluster-init-password=new_password         
        

How do I change the per-node RAM quota?

With the command-line tool (CLI), use couchbase-cli:

couchbase-cli cluster-init -c cluster_IP:8091 
  -u username-p password
  --cluster-init-ramsize=RAM_in_M          
        

How do I change the disk path?

With the command-line tool (CLI), use node-init:

couchbase-cli node-init -c cluster_IP:8091 
  -u username-p password--node-init-data-path=/tmp
        

Why are some clients getting different results than others for the same requests?

This should never happen in a correctly configured Ccouchbase cluster, since Couchbase ensures a consistent view of all data in a cluster. However, if some clients can't reach all the nodes in a cluster (due to firewall or routing rules, for example), it is possible for the same key to end up on more than one cluster node, resulting in inconsistent duplication. Always ensure that all cluster nodes are reachable from every smart client or client-side moxi host.