15.4 Tuning HTTP Listener Settings

The following are the key HTTP listener parameters that affect performance:

• Listener address

  The listener address consists of an IP address and a port number. The host on which an Oracle Traffic Director instance is running can have multiple network interfaces and multiple IP addresses.

  A listener that is configured to listen for client requests on all network interfaces on the host machine would have 0.0.0.0 as its IP address. While specifying 0.0.0.0 as the IP address for a listener is convenient, it results in one additional system call for each connection. For better performance, consider specifying an actual IP address for the listener.

• Number of acceptor threads

  Acceptor threads receive client requests and put them in the connection queue. When an Oracle Traffic Director instance starts, it creates the specified number of acceptor threads for each listener. If the number of acceptor threads for a listener is not specified, Oracle Traffic Director creates one acceptor thread per CPU on the host

  Too many idle acceptor threads place an unnecessary burden on the system, while having too few acceptor threads might result in client requests not being accepted. One acceptor thread per CPU, which is the default setting, is an acceptable trade-off in most situations.

  For HTTP 1.0 workloads, which necessitate opening and closing a relatively large number of connections, the default number of acceptor threads—1 per listener—would be suboptimal. Consider increasing the number of acceptor threads.

• Listen queue size

  As explained earlier, acceptor threads receive client requests and put them in the connection queue. If the operating system has not yet scheduled the acceptor thread, the operating system kernel maintains TCP connections on behalf of Oracle Traffic Director process. The kernel can accept connections up to the limit specified by the listen queue size.

  HTTP 1.0-style workloads can have many connections established and terminated. So if clients experience connection timeouts when an Oracle Traffic Director instance is heavily loaded, you can increase the size of the HTTP listener backlog queue by setting the listen queue size to a larger value.

The plain-text perfdump report shows the IP address and the number of acceptor threads for each HTTP listener in the configuration, as shown in the following example:

ListenSocket ls1:
------------------------
Address                   https://0.0.0.0:1904
Acceptor Threads          1
Default Virtual Server    net-soa

You can change the HTTP listener settings by using either the administration console or the CLI, as described in Section 10.3, "Modifying a Listener."