memcached_behavior_set - libmemcached Documentation

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.

memcached_behavior_set - libmemcached Documentation Manipulate the behavior of a memcached_st structure.

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.

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.

memcached(1)setsockopt(3)libmemcached(3)memcached_strerror(3) 1.1 Mar 31, 2024 MEMCACHED_BEHAVIOR_SET(3)

#include<libmemcached/memcached.h> Compile and link with -lmemcached uint64_tmemcached_behavior_get(memcached_st*ptr,memcached_behavior_tflag)Parameters • ptr -- pointer to initialized memcached_st struct • flag -- memcached_behavior_t to query Returns the vaue set for flagmemcached_return_tmemcached_behavior_set(memcached_st*ptr,memcached_behavior_tflag,uint64_tdata)Parameters • ptr -- pointer to initialized memcached_st struct • flag -- memcached_behavior_t to set • data -- the value to set for flagReturnsmemcached_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. typedefenummemcached_behavior_tmemcached_behavior_tenummemcached_behavior_tenumeratorMEMCACHED_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. enumeratorMEMCACHED_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. enumeratorMEMCACHED_BEHAVIOR_SND_TIMEOUT This sets the microsecond behavior of the socket against the SO_SNDTIMEO flag. enumeratorMEMCACHED_BEHAVIOR_RCV_TIMEOUT This sets the microsecond behavior of the socket against the SO_RCVTIMEO flag. enumeratorMEMCACHED_BEHAVIOR_TCP_NODELAY Disables Nagle's algorithm. See RFC896. enumeratorMEMCACHED_BEHAVIOR_HASH Set the hashalgorithm 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. enumeratorMEMCACHED_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. enumeratorMEMCACHED_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. enumeratorMEMCACHED_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). enumeratorMEMCACHED_BEHAVIOR_KETAMA Sets the default distribution to MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA and the hash to MEMCACHED_HASH_MD5. enumeratorMEMCACHED_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. enumeratorMEMCACHED_BEHAVIOR_KETAMA_HASH Sets the hashingalgorithm for host mapping on continuum. enumeratorMEMCACHED_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. enumeratorMEMCACHED_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'. enumeratorMEMCACHED_BEHAVIOR_USER_DATA Deprecated since version <: 0.30 enumeratorMEMCACHED_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. enumeratorMEMCACHED_BEHAVIOR_VERIFY_KEY Enabling this will cause libmemcached to test all keys to verify that they are valid keys. enumeratorMEMCACHED_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. enumeratorMEMCACHED_BEHAVIOR_CONNECT_TIMEOUT Set the timeout during socket connection in milliseconds. Specifying -1 means an infinite time‐out. enumeratorMEMCACHED_BEHAVIOR_BINARY_PROTOCOL Enable the use of the binary protocol. Please note that you cannot toggle this flag on an open connection. enumeratorMEMCACHED_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). enumeratorMEMCACHED_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). enumeratorMEMCACHED_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. enumeratorMEMCACHED_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). enumeratorMEMCACHED_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. enumeratorMEMCACHED_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. enumeratorMEMCACHED_BEHAVIOR_CORK Deprecated since version ?: This option has been deprecated with the behavior now built in and used appropriately on selected platforms. enumeratorMEMCACHED_BEHAVIOR_KEEPALIVE Enable TCP_KEEPALIVE behavior. enumeratorMEMCACHED_BEHAVIOR_KEEPALIVE_IDLE Specify time, in seconds, to mark a connection as idle. This is only available as an option on Linux. enumeratorMEMCACHED_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. enumeratorMEMCACHED_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. enumeratorMEMCACHED_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. enumeratorMEMCACHED_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. enumeratorMEMCACHED_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. enumeratorMEMCACHED_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. enumeratorMEMCACHED_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. typedefenummemcached_server_distribution_tmemcached_server_distribution_tenummemcached_server_distribution_tenumeratorMEMCACHED_DISTRIBUTION_MODULA Distribute keys by hash modulo number of servers. enumeratorMEMCACHED_DISTRIBUTION_CONSISTENT Alias for MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA. enumeratorMEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA Unweighted consistent key distribution. enumeratorMEMCACHED_DISTRIBUTION_RANDOM Distribute keys by rand(3) modulo number of servers. enumeratorMEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA_SPY Unweighted consistent key distribution compatible with the SPY client. enumeratorMEMCACHED_DISTRIBUTION_CONSISTENT_WEIGHTED Weighted consistent key distribution. enumeratorMEMCACHED_DISTRIBUTION_VIRTUAL_BUCKET Consistent key distribution by virtual buckets.