plucky (3) memcached_behavior_get.3.gz

Provided by: libmemcached-dev_1.1.4-1.1build3_amd64 bug

NAME

       memcached_behavior_get - 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)

              Parametersptr -- 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)

              Parametersptr -- 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)