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.TH "MEMCACHED_BEHAVIOR_SET" "3" "Feb 01, 2024" "1.1" "libmemcached-awesome"
.SH NAME
memcached_behavior_set \- libmemcached Documentation
.sp
Manipulate the behavior of a memcached_st structure.
.SH SYNOPSIS
.INDENT 0.0
.TP
.B #include <libmemcached/memcached.h>
Compile and link with \-lmemcached
.UNINDENT
.INDENT 0.0
.TP
.B uint64_t memcached_behavior_get(\fI\%memcached_st\fP *ptr, \fI\%memcached_behavior_t\fP flag) 
.INDENT 7.0
.TP
.B Parameters
.INDENT 7.0
.IP \(bu 2
\fBptr\fP \-\- pointer to initialized \fI\%memcached_st\fP struct
.IP \(bu 2
\fBflag\fP \-\- \fI\%memcached_behavior_t\fP to query
.UNINDENT
.TP
.B Returns
the vaue set for \fI\%flag\fP
.UNINDENT
.UNINDENT
.INDENT 0.0
.TP
.B \fI\%memcached_return_t\fP memcached_behavior_set(\fI\%memcached_st\fP *ptr, \fI\%memcached_behavior_t\fP flag, uint64_t data) 
.INDENT 7.0
.TP
.B Parameters
.INDENT 7.0
.IP \(bu 2
\fBptr\fP \-\- pointer to initialized \fI\%memcached_st\fP struct
.IP \(bu 2
\fBflag\fP \-\- \fI\%memcached_behavior_t\fP to set
.IP \(bu 2
\fBdata\fP \-\- the value to set for \fI\%flag\fP
.UNINDENT
.TP
.B Returns
\fI\%memcached_return_t\fP indicating success
.UNINDENT
.sp
Changed in version 0.17: The \fI\%data\fP argument of \fI\%memcached_behavior_set()\fP was changed
from taking a pointer to data value, to taking a uin64_t.

.UNINDENT
.INDENT 0.0
.TP
.B typedef enum \fI\%memcached_behavior_t\fP memcached_behavior_t 
.UNINDENT
.INDENT 0.0
.TP
.B enum memcached_behavior_t 
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_USE_UDP 
Causes \fBlibmemcached\fP to use the UDP transport when communicating with a
memcached server. Not all I/O operations are tested when this behavior
is enabled.
.sp
The following operations will return \fI\%MEMCACHED_NOT_SUPPORTED\fP when
executed with \fI\%MEMCACHED_BEHAVIOR_USE_UDP\fP enabled:
.INDENT 7.0
.IP \(bu 2
\fI\%memcached_version()\fP,
.IP \(bu 2
\fI\%memcached_stat()\fP,
.IP \(bu 2
\fI\%memcached_get()\fP,
.IP \(bu 2
\fI\%memcached_get_by_key()\fP,
.IP \(bu 2
\fI\%memcached_mget()\fP,
.IP \(bu 2
\fI\%memcached_mget_by_key()\fP,
.IP \(bu 2
\fI\%memcached_fetch()\fP,
.IP \(bu 2
\fI\%memcached_fetch_result()\fP,
.IP \(bu 2
\fI\%memcached_fetch_execute()\fP\&.
.UNINDENT
.sp
All other operations are tested but are executed in a \(aqfire\-and\-forget\(aq
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.
.sp
\fBlibmemcached\fP does not allow TCP and UDP servers to be shared within
the same \fBlibmemcached\fP client \(aqinstance\(aq. An attempt to add a TCP
server when this behavior is enabled will result in a
\fI\%MEMCACHED_INVALID_HOST_PROTOCOL\fP, as will attempting to add a UDP
server when this behavior has not been enabled.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_NO_BLOCK 
This enables \fBSO_LINGER\fP only, so the \fBclose(2)\fP call on the
socket returns immediately.  I/O is always handled asynchronously in
recent versions of \fBlibmemcached\fP\&.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_SND_TIMEOUT 
This sets the microsecond behavior of the socket against the SO_SNDTIMEO
flag.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_RCV_TIMEOUT 
This sets the microsecond behavior of the socket against the SO_RCVTIMEO
flag.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_TCP_NODELAY 
Disables Nagle\(aqs algorithm.
See \fI\%RFC 896\fP\&.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_HASH 
Set the \fI\%hash algorithm\fP used for keys.
.sp
Each hash has its advantages and its weaknesses. If you don\(aqt know or
don\(aqt care, just go with the default.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_DISTRIBUTION 
Setting a \fI\%memcached_server_distribution_t\fP you can enable different
means of distributing values to servers.
.sp
The default method is \fI\%MEMCACHED_DISTRIBUTION_MODULA\fP (hash of the
key modulo number of servers).
.sp
You can enable consistent hashing by setting
\fI\%MEMCACHED_DISTRIBUTION_CONSISTENT\fP\&. Consistent hashing delivers better
distribution and allows servers to be added to the cluster with minimal
cache losses.
.sp
Currently \fI\%MEMCACHED_DISTRIBUTION_CONSISTENT\fP is an alias for the value
\fI\%MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA\fP\&.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_CACHE_LOOKUPS 
.INDENT 7.0
.INDENT 3.5
Deprecated since version 0.46(?): DNS lookups are now always cached until an error occurs with the
server.

.UNINDENT
.UNINDENT
.sp
Memcached can cache named lookups so that DNS lookups are made only once.
.UNINDENT
.INDENT 7.0
.TP
.B 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).
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_KETAMA 
Sets the default distribution to
\fI\%MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA\fP and the hash to
\fI\%MEMCACHED_HASH_MD5\fP\&.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_KETAMA_WEIGHTED 
Sets the default distribution to
\fI\%MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA\fP with the weighted tests.
Makes the default hashing algorithm for keys use \fI\%MEMCACHED_HASH_MD5\fP\&.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_KETAMA_HASH 
Sets the \fI\%hashing algorithm\fP for host mapping on continuum.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_KETAMA_COMPAT 
Sets the compatibility mode. The value can be set to either
\fBMEMCACHED_KETAMA_COMPAT_LIBMEMCACHED\fP (this is the default) or
\fBMEMCACHED_KETAMA_COMPAT_SPY\fP to be compatible with the SPY Memcached
client for Java.
.UNINDENT
.INDENT 7.0
.TP
.B 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
\fI\%memcached_behavior_set()\fP to change this value (this requires casting).
For \fI\%memcached_behavior_get()\fP a \(aqsigned int\(aq value will be cast and
returned as \(aqunsigned long long\(aq.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_USER_DATA 
Deprecated since version <: 0.30

.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_BUFFER_REQUESTS 
Enabling buffered IO causes commands to \(dqbuffer\(dq 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.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_VERIFY_KEY 
Enabling this will cause \fBlibmemcached\fP to test all keys to verify that
they are valid keys.
.UNINDENT
.INDENT 7.0
.TP
.B 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.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_CONNECT_TIMEOUT 
Set the timeout during socket connection in milliseconds.
Specifying \-1 means an infinite time‐out.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_BINARY_PROTOCOL 
Enable the use of the binary protocol. Please note that you cannot
toggle this flag on an open connection.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_IO_MSG_WATERMARK 
Set this value to tune the number of messages that may be sent before
\fBlibmemcached\fP should start to automatically drain the input queue.
.sp
Setting this value to high, may cause \fBlibmemcached\fP to deadlock (trying
to send data, but the send will block because the input buffer in the
kernel is full).
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_IO_BYTES_WATERMARK 
Set this value to tune the number of bytes that may be sent before
\fBlibmemcached\fP should start to automatically drain the input queue (need
at least 10 IO requests sent without reading the input buffer).
.sp
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).
.UNINDENT
.INDENT 7.0
.TP
.B 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.
.sp
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.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_NOREPLY 
Set this value to specify that you really don\(aqt care about the result
from your storage commands (set, add, replace, append, prepend).
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_NUMBER_OF_REPLICAS 
Specify the number of replicas \fBlibmemcached\fP should store of each item
(on different servers).
.sp
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 \(aqn\(aq next servers specified in your
server list).
.sp
Requires the binary protocol and only supports (M)GET/SET/DELETE.
.sp
\fBNOTE\fP: \fBlibmemcached\fP does not guarantee nor enforce any consistency.
.UNINDENT
.INDENT 7.0
.TP
.B 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 \(aqn\(aq replicas.
.sp
This allows distributing read load to multiple servers with the expense
of more write traffic.
.sp
\fBNOTE\fP: Only errors to communicate with a server are considered
failures, so \fI\%MEMCACHED_NOTFOUND\fP does \fInot\fP account for failure.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_CORK 
Deprecated since version ?: This option has been deprecated with the behavior now built in and
used appropriately on selected platforms.

.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_KEEPALIVE 
Enable TCP_KEEPALIVE behavior.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_KEEPALIVE_IDLE 
Specify time, in seconds, to mark a connection as idle. This is only
available as an option on Linux.
.UNINDENT
.INDENT 7.0
.TP
.B 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.
.sp
If an error occurs you can check the last cached errno to find the
specific error.
.UNINDENT
.INDENT 7.0
.TP
.B 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.
.sp
If an error occurs you can check the last cached errno to find the
specific error.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT 
Deprecated since version 0.48: See \fI\%MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS\fP

.sp
Set this value to enable the server be removed after continuous
\fI\%MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT\fP times connection failure.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_AUTO_EJECT_HOSTS 
Deprecated since version 0.48: See \fI\%MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS\fP

.sp
If enabled any hosts which have been flagged as disabled will be removed
from the list of servers in the \fI\%memcached_st\fP structure. This must be
used in combination with \fI\%MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT\fP\&.
.UNINDENT
.INDENT 7.0
.TP
.B 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 \fI\%memcached_st\fP structure.
.UNINDENT
.INDENT 7.0
.TP
.B 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.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_BEHAVIOR_HASH_WITH_PREFIX_KEY 
When enabled the prefix key will be added to the key when determining
server by hash. See \fI\%MEMCACHED_CALLBACK_NAMESPACE\fP for additional
information.
.UNINDENT
.UNINDENT
.INDENT 0.0
.TP
.B typedef enum \fI\%memcached_server_distribution_t\fP memcached_server_distribution_t 
.UNINDENT
.INDENT 0.0
.TP
.B enum memcached_server_distribution_t 
.INDENT 7.0
.TP
.B enumerator MEMCACHED_DISTRIBUTION_MODULA 
Distribute keys by hash modulo number of servers.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_DISTRIBUTION_CONSISTENT 
Alias for \fI\%MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA\fP\&.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA 
Unweighted consistent key distribution.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_DISTRIBUTION_RANDOM 
Distribute keys by \fBrand(3)\fP modulo number of servers.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA_SPY 
Unweighted consistent key distribution compatible with the SPY client.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_DISTRIBUTION_CONSISTENT_WEIGHTED 
Weighted consistent key distribution.
.UNINDENT
.INDENT 7.0
.TP
.B enumerator MEMCACHED_DISTRIBUTION_VIRTUAL_BUCKET 
Consistent key distribution by virtual buckets.
.UNINDENT
.UNINDENT
.SH DESCRIPTION
.sp
\fBlibmemcached\fP behavior can be modified by using \fI\%memcached_behavior_set()\fP\&.
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, \fI\%memcached_set()\fP will always respond with \fI\%MEMCACHED_SUCCESS\fP).
.sp
\fI\%memcached_behavior_get()\fP takes a behavior \fBflag\fP and returns whether or not
that behavior is currently enabled in the client.
.sp
\fI\%memcached_behavior_set()\fP changes the value of a particular option of the client.
It takes both a \fBflag\fP and a \fBvalue\fP\&. For simple on or off options you just
need to pass in a value of 1. Calls to \fI\%memcached_behavior_set()\fP will flush and
reset all connections.
.SH RETURN VALUE
.sp
\fI\%memcached_behavior_get()\fP returns either the current value of the key, or 0
or 1 on simple flag behaviors (1 being enabled). \fI\%memcached_behavior_set()\fP
returns failure or success.
.SH NOTES
.sp
The \fBdata\fP argument of \fI\%memcached_behavior_set()\fP was changed in version
0.17 from taking a pointer to data value, to taking a uin64_t.
.SH SEE ALSO
.sp
\fBmemcached(1)\fP
\fBsetsockopt(3)\fP
\fBlibmemcached(3)\fP
\fBmemcached_strerror(3)\fP
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