Provided by: libmemcached-dev_1.1.4-1.1build3_amd64 
NAME
memcached_behavior - libmemcached Documentation
Manipulate the behavior of a memcached_st structure.
SYNOPSIS
#include <libmemcached/memcached.h>
Compile and link with -lmemcached
uint64_t memcached_behavior_get(memcached_st *ptr, memcached_behavior_t flag)
Parameters
• ptr -- pointer to initialized memcached_st struct
• flag -- memcached_behavior_t to query
Returns
the vaue set for flag
memcached_return_t memcached_behavior_set(memcached_st *ptr, memcached_behavior_t flag,
uint64_t data)
Parameters
• ptr -- pointer to initialized memcached_st struct
• flag -- memcached_behavior_t to set
• data -- the value to set for flag
Returns
memcached_return_t indicating success
Changed in version 0.17: The data argument of memcached_behavior_set() was changed
from taking a pointer to data value, to taking a uin64_t.
typedef enum memcached_behavior_t memcached_behavior_t
enum memcached_behavior_t
enumerator MEMCACHED_BEHAVIOR_USE_UDP
Causes libmemcached to use the UDP transport when communicating with a
memcached server. Not all I/O operations are tested when this behavior is
enabled.
The following operations will return MEMCACHED_NOT_SUPPORTED when executed
with MEMCACHED_BEHAVIOR_USE_UDP enabled:
• memcached_version(),
• memcached_stat(),
• memcached_get(),
• memcached_get_by_key(),
• memcached_mget(),
• memcached_mget_by_key(),
• memcached_fetch(),
• memcached_fetch_result(),
• memcached_fetch_execute().
All other operations are tested but are executed in a 'fire-and-forget'
mode, in which once the client has executed the operation, no attempt will
be made to ensure the operation has been received and acted on by the
server.
libmemcached does not allow TCP and UDP servers to be shared within the same
libmemcached client 'instance'. An attempt to add a TCP server when this
behavior is enabled will result in a MEMCACHED_INVALID_HOST_PROTOCOL, as
will attempting to add a UDP server when this behavior has not been enabled.
enumerator MEMCACHED_BEHAVIOR_NO_BLOCK
This enables SO_LINGER only, so the close(2) call on the socket returns
immediately. I/O is always handled asynchronously in recent versions of
libmemcached.
enumerator MEMCACHED_BEHAVIOR_SND_TIMEOUT
This sets the microsecond behavior of the socket against the SO_SNDTIMEO
flag.
enumerator MEMCACHED_BEHAVIOR_RCV_TIMEOUT
This sets the microsecond behavior of the socket against the SO_RCVTIMEO
flag.
enumerator MEMCACHED_BEHAVIOR_TCP_NODELAY
Disables Nagle's algorithm. See RFC 896.
enumerator MEMCACHED_BEHAVIOR_HASH
Set the hash algorithm used for keys.
Each hash has its advantages and its weaknesses. If you don't know or don't
care, just go with the default.
enumerator MEMCACHED_BEHAVIOR_DISTRIBUTION
Setting a memcached_server_distribution_t you can enable different means of
distributing values to servers.
The default method is MEMCACHED_DISTRIBUTION_MODULA (hash of the key modulo
number of servers).
You can enable consistent hashing by setting
MEMCACHED_DISTRIBUTION_CONSISTENT. Consistent hashing delivers better
distribution and allows servers to be added to the cluster with minimal
cache losses.
Currently MEMCACHED_DISTRIBUTION_CONSISTENT is an alias for the value
MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA.
enumerator MEMCACHED_BEHAVIOR_CACHE_LOOKUPS
Deprecated since version 0.46(?): DNS lookups are now always cached until
an error occurs with the server.
Memcached can cache named lookups so that DNS lookups are made only once.
enumerator MEMCACHED_BEHAVIOR_SUPPORT_CAS
Support CAS operations (this is not enabled by default at this point in the
server since it imposes a slight performance penalty).
enumerator MEMCACHED_BEHAVIOR_KETAMA
Sets the default distribution to MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA
and the hash to MEMCACHED_HASH_MD5.
enumerator MEMCACHED_BEHAVIOR_KETAMA_WEIGHTED
Sets the default distribution to MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA
with the weighted tests. Makes the default hashing algorithm for keys use
MEMCACHED_HASH_MD5.
enumerator MEMCACHED_BEHAVIOR_KETAMA_HASH
Sets the hashing algorithm for host mapping on continuum.
enumerator MEMCACHED_BEHAVIOR_KETAMA_COMPAT
Sets the compatibility mode. The value can be set to either
MEMCACHED_KETAMA_COMPAT_LIBMEMCACHED (this is the default) or
MEMCACHED_KETAMA_COMPAT_SPY to be compatible with the SPY Memcached client
for Java.
enumerator MEMCACHED_BEHAVIOR_POLL_TIMEOUT
Modify the timeout in milliseconds value that is used by poll. The default
value is -1. An signed int must be passed to memcached_behavior_set() to
change this value (this requires casting). For memcached_behavior_get() a
'signed int' value will be cast and returned as 'unsigned long long'.
enumerator MEMCACHED_BEHAVIOR_USER_DATA
Deprecated since version <: 0.30
enumerator MEMCACHED_BEHAVIOR_BUFFER_REQUESTS
Enabling buffered IO causes commands to "buffer" instead of being sent. Any
action that gets data causes this buffer to be be sent to the remote
connection. Quiting the connection or closing down the connection will also
cause the buffered data to be pushed to the remote connection.
enumerator MEMCACHED_BEHAVIOR_VERIFY_KEY
Enabling this will cause libmemcached to test all keys to verify that they
are valid keys.
enumerator MEMCACHED_BEHAVIOR_SORT_HOSTS
Enabling this will cause hosts that are added to be placed in the host list
in sorted order. This will defeat consistent hashing.
enumerator MEMCACHED_BEHAVIOR_CONNECT_TIMEOUT
Set the timeout during socket connection in milliseconds. Specifying -1
means an infinite time‐out.
enumerator MEMCACHED_BEHAVIOR_BINARY_PROTOCOL
Enable the use of the binary protocol. Please note that you cannot toggle
this flag on an open connection.
enumerator MEMCACHED_BEHAVIOR_IO_MSG_WATERMARK
Set this value to tune the number of messages that may be sent before
libmemcached should start to automatically drain the input queue.
Setting this value to high, may cause libmemcached to deadlock (trying to
send data, but the send will block because the input buffer in the kernel is
full).
enumerator MEMCACHED_BEHAVIOR_IO_BYTES_WATERMARK
Set this value to tune the number of bytes that may be sent before
libmemcached should start to automatically drain the input queue (need at
least 10 IO requests sent without reading the input buffer).
Setting this value to high, may cause libmemcached to deadlock (trying to
send data, but the send will block because the input buffer in the kernel is
full).
enumerator MEMCACHED_BEHAVIOR_IO_KEY_PREFETCH
The binary protocol works a bit different than the textual protocol in that
a multiget is implemented as a pipe of single get-operations which are sent
to the server in a chunk.
If you are using large multigets from your application, you may improve the
latency of the gets by setting this value so you send out the first chunk of
requests when you hit the specified limit. It allows the servers to start
processing the requests to send the data back while the rest of the requests
are created and sent to the server.
enumerator MEMCACHED_BEHAVIOR_NOREPLY
Set this value to specify that you really don't care about the result from
your storage commands (set, add, replace, append, prepend).
enumerator MEMCACHED_BEHAVIOR_NUMBER_OF_REPLICAS
Specify the number of replicas libmemcached should store of each item (on
different servers).
This replication does not dedicate certain memcached servers to store the
replicas in, but instead it will store the replicas together with all of the
other objects (on the 'n' next servers specified in your server list).
Requires the binary protocol and only supports (M)GET/SET/DELETE.
NOTE: libmemcached does not guarantee nor enforce any consistency.
enumerator MEMCACHED_BEHAVIOR_RANDOMIZE_REPLICA_READ
Allows randomizing the replica reads starting point. Normally the read is
done from primary server and in case of failure the read is done from
primary + 1, then primary + 2 all the way to 'n' replicas.
This allows distributing read load to multiple servers with the expense of
more write traffic.
NOTE: Only errors to communicate with a server are considered failures, so
MEMCACHED_NOTFOUND does not account for failure.
enumerator MEMCACHED_BEHAVIOR_CORK
Deprecated since version ?: This option has been deprecated with the
behavior now built in and used appropriately on selected platforms.
enumerator MEMCACHED_BEHAVIOR_KEEPALIVE
Enable TCP_KEEPALIVE behavior.
enumerator MEMCACHED_BEHAVIOR_KEEPALIVE_IDLE
Specify time, in seconds, to mark a connection as idle. This is only
available as an option on Linux.
enumerator MEMCACHED_BEHAVIOR_SOCKET_SEND_SIZE
Find the current size of SO_SNDBUF. A value of 0 means either an error
occurred or no hosts were available. It is safe to assume system default if
this occurs.
If an error occurs you can check the last cached errno to find the specific
error.
enumerator MEMCACHED_BEHAVIOR_SOCKET_RECV_SIZE
Find the current size of SO_RCVBUF. A value of 0 means either an error
occurred or no hosts were available. It is safe to assume system default if
this occurs.
If an error occurs you can check the last cached errno to find the specific
error.
enumerator MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT
Deprecated since version 0.48: See MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS
Set this value to enable the server be removed after continuous
MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT times connection failure.
enumerator MEMCACHED_BEHAVIOR_AUTO_EJECT_HOSTS
Deprecated since version 0.48: See MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS
If enabled any hosts which have been flagged as disabled will be removed
from the list of servers in the memcached_st structure. This must be used in
combination with MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT.
enumerator MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS
If enabled any hosts which have been flagged as disabled will be removed
from the list of servers in the memcached_st structure.
enumerator MEMCACHED_BEHAVIOR_RETRY_TIMEOUT
When enabled a host which is problematic will only be checked for usage
based on the amount of time set by this behavior. The value is in seconds.
enumerator MEMCACHED_BEHAVIOR_HASH_WITH_PREFIX_KEY
When enabled the prefix key will be added to the key when determining server
by hash. See MEMCACHED_CALLBACK_NAMESPACE for additional information.
typedef enum memcached_server_distribution_t memcached_server_distribution_t
enum memcached_server_distribution_t
enumerator MEMCACHED_DISTRIBUTION_MODULA
Distribute keys by hash modulo number of servers.
enumerator MEMCACHED_DISTRIBUTION_CONSISTENT
Alias for MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA.
enumerator MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA
Unweighted consistent key distribution.
enumerator MEMCACHED_DISTRIBUTION_RANDOM
Distribute keys by rand(3) modulo number of servers.
enumerator MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA_SPY
Unweighted consistent key distribution compatible with the SPY client.
enumerator MEMCACHED_DISTRIBUTION_CONSISTENT_WEIGHTED
Weighted consistent key distribution.
enumerator MEMCACHED_DISTRIBUTION_VIRTUAL_BUCKET
Consistent key distribution by virtual buckets.
DESCRIPTION
libmemcached behavior can be modified by using memcached_behavior_set(). Default behavior
is the library strives to be quick and accurate. Some behavior, while being faster, can
also result in not entirely accurate behavior (for instance, memcached_set() will always
respond with MEMCACHED_SUCCESS).
memcached_behavior_get() takes a behavior flag and returns whether or not that behavior is
currently enabled in the client.
memcached_behavior_set() changes the value of a particular option of the client. It takes
both a flag and a value. For simple on or off options you just need to pass in a value of
1. Calls to memcached_behavior_set() will flush and reset all connections.
RETURN VALUE
memcached_behavior_get() returns either the current value of the key, or 0 or 1 on simple
flag behaviors (1 being enabled). memcached_behavior_set() returns failure or success.
NOTES
The data argument of memcached_behavior_set() was changed in version 0.17 from taking a
pointer to data value, to taking a uin64_t.
SEE ALSO
memcached(1) setsockopt(3) libmemcached(3) memcached_strerror(3)