Directive: SSLSessionCache
Description: Type of the global/inter-process SSL Session Cache
Syntax: SSLSessionCache type
Default: SSLSessionCache none
Context: server config
Status: Extension
Module: mod_ssl
This configures the storage type of the global/inter-process SSL Session Cache.
This cache is an optional facility which speeds up parallel request processing.
For requests to the same server process (via HTTP keep-alive), OpenSSL already
caches the SSL session information locally. But because modern clients request
inlined images and other data via parallel requests (usually up to four parallel
requests are common) those requests are served by different pre-forked server
processes. Here an inter-process cache helps to avoid unneccessary session handshakes.
The following four storage types are currently supported:
none
This disables the global/inter-process Session Cache. This will incur a noticeable
speed penalty and may cause problems if using certain browsers, particularly if client
certificates are enabled. This setting is not recommended.
nonenotnull
This disables any global/inter-process Session Cache. However it does force OpenSSL to
send a non-null session ID to accommodate buggy clients that require one.
dbm:/path/to/datafile
This makes use of a DBM hashfile on the local disk to synchronize the local OpenSSL
memory caches of the server processes. This session cache may suffer reliability issues
under high load.
shm:/path/to/datafile[(size)]
This makes use of a high-performance cyclic buffer (approx. size bytes in size) inside
a shared memory segment in RAM (established via /path/to/datafile) to synchronize the
local OpenSSL memory caches of the server processes. This is the recommended session cache.
dc:UNIX:/path/to/socket
This makes use of the distcache distributed session caching libraries. The argument
should specify the location of the server or proxy to be used using the distcache
address syntax; for example, UNIX:/path/to/socket specifies a UNIX domain socket
(typically a local dc_client proxy); IP:server.example.com:9001 specifies an IP address.
Examples
SSLSessionCache dbm:/usr/local/apache/logs/ssl_gcache_data
SSLSessionCache shm:/usr/local/apache/logs/ssl_gcache_data(512000)
