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    Runtime Configuration

    The behaviour of these functions is affected by settings in php.ini.

    Memcache Configuration Options
    Name Default Changeable Changelog
    memcache.allow_failover "1" INI_ALL Available since memcache 2.0.2.
    memcache.max_failover_attempts "20" INI_ALL Available since memcache 2.1.0.
    memcache.chunk_size "8192" INI_ALL Available since memcache 2.0.2.
    memcache.default_port "11211" INI_ALL Available since memcache 2.0.2.
    memcache.hash_strategy "standard" INI_ALL Available since memcache 2.2.0.
    memcache.hash_function "crc32" INI_ALL Available since memcache 2.2.0.
    memcache.protocol ascii INI_ALL Supported since memcache 3.0.0
    memcache.redundancy 1 INI_ALL Supported since memcache 3.0.0
    memcache.session_redundancy 2 INI_ALL Supported since memcache 3.0.0
    memcache.compress_threshold 20000 INI_ALL Supported since memcache 3.0.3
    memcache.lock_timeout 15 INI_ALL Supported since memcache 3.0.4
    Session Configuration Options Affecting Memcache Behavior
    Name Default Changeable Changelog
    session.save_handler "files" INI_ALL Supported since memcache 2.1.2
    session.save_path "" INI_ALL Supported since memcache 2.1.2
    For further details and definitions of the INI_* modes, see the Where a configuration setting may be set.

    Here's a short explanation of the configuration directives.

    memcache.allow_failover bool

    Whether to transparently failover to other servers on errors.

    memcache.max_failover_attempts int

    Defines how many servers to try when setting and getting data. Used only in conjunction with memcache.allow_failover.

    memcache.chunk_size int

    Data will be transferred in chunks of this size, setting the value lower requires more network writes. Try increasing this value to 32768 if noticing otherwise inexplicable slowdowns.

    memcache.default_port string

    The default TCP port number to use when connecting to the memcached server if no other port is specified.

    memcache.hash_strategy string

    Controls which strategy to use when mapping keys to servers. Set this value to consistent to enable consistent hashing which allows servers to be added or removed from the pool without causing keys to be remapped. Setting this value to standard results in the old strategy being used.

    memcache.hash_function string

    Controls which hash function to apply when mapping keys to servers, crc32 uses the standard CRC32 hash while fnv uses FNV-1a.

    memcache.protocol string

    memcache.redundancy int

    memcache.session_redundancy int

    memcache.compress_threshold int

    memcache.lock_timeout int

    session.save_handler string

    Use memcache as a session handler by setting this value to memcache.

    session.save_path string

    Defines a comma separated of server urls to use for session storage, for example "tcp://host1:11211, tcp://host2:11211".

    Each url may contain parameters which are applied to that server, they are the same as for the Memcache::addServer() method. For example "tcp://host1:11211?persistent=1&weight=1&timeout=1&retry_interval=15"

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    User Contributed Notes 1 note

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    kross at escapistmag dot com
    14 years ago
    There's a currently undocumented variable that is now available (you can see it in php_info()) for session handling:

    memcache.session_redundancy

    The default seems to be "2", and it is supposed to influence how many copies of a particular session object that Memcache will store for failover purposes (so with a redundancy of 2, it will store a session on 2 different shards).

    This will add slight overhead with extra writes, but overall seems worth it for purposes of failover.
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