PHP: Persistent connections for PHP clients are actually persistent memory that we use across multiple requests in a PHP process. Typically you use one PHP process per system process. The web server that is currently in use in your system will determine this. To configure the PHP SDK to maintain a persistent connection you would use these parameters in your connection:

$cb = new Couchbase("192.168.1.200:8091", "default", "", "default", true);

// uses the default bucket

This example uses the default bucket. Arguments include host:port, username, password, bucket name, and true indicates we want to use a persistent connection. For more information, refer to the Couchbase PHP SDK Language Reference.

Java: When you create connection with the Java SDK, the connection is a thread-safe object that can be shared across multiple processes. The alternative is that you can create a connection pool which contains a multiple connection objects.

For more information, see Couchbase Java SDK: Connecting to the Server.

.Net: Connections that you create with the .net SDK are also thread-safe objects; for persisted connections, you can use a connection pool which contains multiple connection objects. You should create only a single static instance of a Couchbase client per bucket, in accordance with .Net framework. The persistent client will maintain connection pools per server node. For more information, see MSDN: AppDomain Class

You can persist a Couchbase client storing it in a way such that the Ruby garbage collector does not remove from memory. To do this, you can create a singleton object that contains the client instance and the connection information. You should access the class-level method, Couchbase.bucket instead of Couchbase.connect to get the client instance.

When you use Couchbase.bucket it will create a new client object when you first call it and then store the object in thread storage. If the thread is still alive when the next request is made to the ruby process, the SDK will not create a new client instance, but rather use the existing one:

# Simple example to connect using thread local singleton

Couchbase.connection_options = {
  :bucket => "my",
  :hostname => "example.com",
  :password => "secret"
}

# this call will user connection_options to initialize new connection. 
# By default Couchbase.connection_options can be empty
Couchbase.bucket.set("foo", "bar")

# Amend the options of the singleton connection in run-time
Couchbase.bucket.reconnect(:bucket => "another")

The first example demonstrates how you can create a client instance as a singleton object, the second one will use the class-level Couchbase.bucket constructor to create a persistent connection. The last example demonstrates how you can update the properties of the singleton connection if you reconnect.