1MEMCACHED_BEHAVIOR(3) libmemcached-awesome MEMCACHED_BEHAVIOR(3)
2
6 memcached_behavior - libmemcached Documentation
7 Manipulate the behavior of a memcached_st structure.
9
11 #include <libmemcached/memcached.h>
12 Compile and link with -lmemcached
13 uint64_t memcached_behavior_get(memcached_st *ptr, memcached_behavior_t
15 flag)
16 Parameters
18 • ptr -- pointer to initialized memcached_st struct
20 • flag -- memcached_behavior_t to query
22 Returns
24 the vaue set for flag
25 memcached_return_t memcached_behavior_set(memcached_st *ptr,
27 memcached_behavior_t flag, uint64_t data)
28 Parameters
30 • ptr -- pointer to initialized memcached_st struct
32 • flag -- memcached_behavior_t to set
34 • data -- the value to set for flag
36 Returns
38 memcached_return_t indicating success
39 Changed in version 0.17: The data argument of
41 memcached_behavior_set() was changed from taking a pointer to
42 data value, to taking a uin64_t.
43 typedef enum memcached_behavior_t memcached_behavior_t
46 enum memcached_behavior_t
48 enumerator MEMCACHED_BEHAVIOR_USE_UDP
50 Causes libmemcached to use the UDP transport when commu‐
51 nicating with a memcached server. Not all I/O operations
52 are tested when this behavior is enabled.
53 The following operations will return
55 MEMCACHED_NOT_SUPPORTED when executed with
56 MEMCACHED_BEHAVIOR_USE_UDP enabled:
57 • memcached_version(),
59 • memcached_stat(),
61 • memcached_get(),
63 • memcached_get_by_key(),
65 • memcached_mget(),
67 • memcached_mget_by_key(),
69 • memcached_fetch(),
71 • memcached_fetch_result(),
73 • memcached_fetch_execute().
75 All other operations are tested but are executed in a
77 'fire-and-forget' mode, in which once the client has exe‐
78 cuted the operation, no attempt will be made to ensure
79 the operation has been received and acted on by the
80 server.
81 libmemcached does not allow TCP and UDP servers to be
83 shared within the same libmemcached client 'instance'. An
84 attempt to add a TCP server when this behavior is enabled
85 will result in a MEMCACHED_INVALID_HOST_PROTOCOL, as will
86 attempting to add a UDP server when this behavior has not
87 been enabled.
88 enumerator MEMCACHED_BEHAVIOR_NO_BLOCK
90 This enables SO_LINGER only, so the close(2) call on the
91 socket returns immediately. I/O is always handled asyn‐
92 chronously in recent versions of libmemcached.
93 enumerator MEMCACHED_BEHAVIOR_SND_TIMEOUT
95 This sets the microsecond behavior of the socket against
96 the SO_SNDTIMEO flag.
97 enumerator MEMCACHED_BEHAVIOR_RCV_TIMEOUT
99 This sets the microsecond behavior of the socket against
100 the SO_RCVTIMEO flag.
101 enumerator MEMCACHED_BEHAVIOR_TCP_NODELAY
103 Disables Nagle's algorithm. See RFC 896.
104 enumerator MEMCACHED_BEHAVIOR_HASH
106 Set the hash algorithm used for keys.
107 Each hash has its advantages and its weaknesses. If you
109 don't know or don't care, just go with the default.
110 enumerator MEMCACHED_BEHAVIOR_DISTRIBUTION
112 Setting a memcached_server_distribution_t you can enable
113 different means of distributing values to servers.
114 The default method is MEMCACHED_DISTRIBUTION_MODULA (hash
116 of the key modulo number of servers).
117 You can enable consistent hashing by setting
119 MEMCACHED_DISTRIBUTION_CONSISTENT. Consistent hashing de‐
120 livers better distribution and allows servers to be added
121 to the cluster with minimal cache losses.
122 Currently MEMCACHED_DISTRIBUTION_CONSISTENT is an alias
124 for the value MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA.
125 enumerator MEMCACHED_BEHAVIOR_CACHE_LOOKUPS
127 Deprecated since version 0.46(?): DNS lookups are now
128 always cached until an error occurs with the server.
129 Memcached can cache named lookups so that DNS lookups are
132 made only once.
133 enumerator MEMCACHED_BEHAVIOR_SUPPORT_CAS
135 Support CAS operations (this is not enabled by default at
136 this point in the server since it imposes a slight per‐
137 formance penalty).
138 enumerator MEMCACHED_BEHAVIOR_KETAMA
140 Sets the default distribution to
141 MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA and the hash to
142 MEMCACHED_HASH_MD5.
143 enumerator MEMCACHED_BEHAVIOR_KETAMA_WEIGHTED
145 Sets the default distribution to
146 MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA with the
147 weighted tests. Makes the default hashing algorithm for
148 keys use MEMCACHED_HASH_MD5.
149 enumerator MEMCACHED_BEHAVIOR_KETAMA_HASH
151 Sets the hashing algorithm for host mapping on continuum.
152 enumerator MEMCACHED_BEHAVIOR_KETAMA_COMPAT
154 Sets the compatibility mode. The value can be set to ei‐
155 ther MEMCACHED_KETAMA_COMPAT_LIBMEMCACHED (this is the
156 default) or MEMCACHED_KETAMA_COMPAT_SPY to be compatible
157 with the SPY Memcached client for Java.
158 enumerator MEMCACHED_BEHAVIOR_POLL_TIMEOUT
160 Modify the timeout in milliseconds value that is used by
161 poll. The default value is -1. An signed int must be
162 passed to memcached_behavior_set() to change this value
163 (this requires casting). For memcached_behavior_get() a
164 'signed int' value will be cast and returned as 'unsigned
165 long long'.
166 enumerator MEMCACHED_BEHAVIOR_USER_DATA
168 Deprecated since version <: 0.30
169 enumerator MEMCACHED_BEHAVIOR_BUFFER_REQUESTS
172 Enabling buffered IO causes commands to "buffer" instead
173 of being sent. Any action that gets data causes this
174 buffer to be be sent to the remote connection. Quiting
175 the connection or closing down the connection will also
176 cause the buffered data to be pushed to the remote con‐
177 nection.
178 enumerator MEMCACHED_BEHAVIOR_VERIFY_KEY
180 Enabling this will cause libmemcached to test all keys to
181 verify that they are valid keys.
182 enumerator MEMCACHED_BEHAVIOR_SORT_HOSTS
184 Enabling this will cause hosts that are added to be
185 placed in the host list in sorted order. This will defeat
186 consistent hashing.
187 enumerator MEMCACHED_BEHAVIOR_CONNECT_TIMEOUT
189 Set the timeout during socket connection in milliseconds.
190 Specifying -1 means an infinite time‐out.
191 enumerator MEMCACHED_BEHAVIOR_BINARY_PROTOCOL
193 Enable the use of the binary protocol. Please note that
194 you cannot toggle this flag on an open connection.
195 enumerator MEMCACHED_BEHAVIOR_IO_MSG_WATERMARK
197 Set this value to tune the number of messages that may be
198 sent before libmemcached should start to automatically
199 drain the input queue.
200 Setting this value to high, may cause libmemcached to
202 deadlock (trying to send data, but the send will block
203 because the input buffer in the kernel is full).
204 enumerator MEMCACHED_BEHAVIOR_IO_BYTES_WATERMARK
206 Set this value to tune the number of bytes that may be
207 sent before libmemcached should start to automatically
208 drain the input queue (need at least 10 IO requests sent
209 without reading the input buffer).
210 Setting this value to high, may cause libmemcached to
212 deadlock (trying to send data, but the send will block
213 because the input buffer in the kernel is full).
214 enumerator MEMCACHED_BEHAVIOR_IO_KEY_PREFETCH
216 The binary protocol works a bit different than the tex‐
217 tual protocol in that a multiget is implemented as a pipe
218 of single get-operations which are sent to the server in
219 a chunk.
220 If you are using large multigets from your application,
222 you may improve the latency of the gets by setting this
223 value so you send out the first chunk of requests when
224 you hit the specified limit. It allows the servers to
225 start processing the requests to send the data back while
226 the rest of the requests are created and sent to the
227 server.
228 enumerator MEMCACHED_BEHAVIOR_NOREPLY
230 Set this value to specify that you really don't care
231 about the result from your storage commands (set, add,
232 replace, append, prepend).
233 enumerator MEMCACHED_BEHAVIOR_NUMBER_OF_REPLICAS
235 Specify the number of replicas libmemcached should store
236 of each item (on different servers).
237 This replication does not dedicate certain memcached
239 servers to store the replicas in, but instead it will
240 store the replicas together with all of the other objects
241 (on the 'n' next servers specified in your server list).
242 Requires the binary protocol and only supports
244 (M)GET/SET/DELETE.
245 NOTE: libmemcached does not guarantee nor enforce any
247 consistency.
248 enumerator MEMCACHED_BEHAVIOR_RANDOMIZE_REPLICA_READ
250 Allows randomizing the replica reads starting point. Nor‐
251 mally the read is done from primary server and in case of
252 failure the read is done from primary + 1, then primary +
253 2 all the way to 'n' replicas.
254 This allows distributing read load to multiple servers
256 with the expense of more write traffic.
257 NOTE: Only errors to communicate with a server are con‐
259 sidered failures, so MEMCACHED_NOTFOUND does not account
260 for failure.
261 enumerator MEMCACHED_BEHAVIOR_CORK
263 Deprecated since version ?: This option has been depre‐
264 cated with the behavior now built in and used appropri‐
265 ately on selected platforms.
266 enumerator MEMCACHED_BEHAVIOR_KEEPALIVE
269 Enable TCP_KEEPALIVE behavior.
270 enumerator MEMCACHED_BEHAVIOR_KEEPALIVE_IDLE
272 Specify time, in seconds, to mark a connection as idle.
273 This is only available as an option on Linux.
274 enumerator MEMCACHED_BEHAVIOR_SOCKET_SEND_SIZE
276 Find the current size of SO_SNDBUF. A value of 0 means
277 either an error occurred or no hosts were available. It
278 is safe to assume system default if this occurs.
279 If an error occurs you can check the last cached errno to
281 find the specific error.
282 enumerator MEMCACHED_BEHAVIOR_SOCKET_RECV_SIZE
284 Find the current size of SO_RCVBUF. A value of 0 means
285 either an error occurred or no hosts were available. It
286 is safe to assume system default if this occurs.
287 If an error occurs you can check the last cached errno to
289 find the specific error.
290 enumerator MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT
292 Deprecated since version 0.48: See
293 MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS
294 Set this value to enable the server be removed after con‐
297 tinuous MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT times
298 connection failure.
299 enumerator MEMCACHED_BEHAVIOR_AUTO_EJECT_HOSTS
301 Deprecated since version 0.48: See
302 MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS
303 If enabled any hosts which have been flagged as disabled
306 will be removed from the list of servers in the
307 memcached_st structure. This must be used in combination
308 with MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT.
309 enumerator MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS
311 If enabled any hosts which have been flagged as disabled
312 will be removed from the list of servers in the
313 memcached_st structure.
314 enumerator MEMCACHED_BEHAVIOR_RETRY_TIMEOUT
316 When enabled a host which is problematic will only be
317 checked for usage based on the amount of time set by this
318 behavior. The value is in seconds.
319 enumerator MEMCACHED_BEHAVIOR_HASH_WITH_PREFIX_KEY
321 When enabled the prefix key will be added to the key when
322 determining server by hash. See
323 MEMCACHED_CALLBACK_NAMESPACE for additional information.
324 typedef enum memcached_server_distribution_t memcached_server_distribu‐
326 tion_t
327 enum memcached_server_distribution_t
329 enumerator MEMCACHED_DISTRIBUTION_MODULA
331 Distribute keys by hash modulo number of servers.
332 enumerator MEMCACHED_DISTRIBUTION_CONSISTENT
334 Alias for MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA.
335 enumerator MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA
337 Unweighted consistent key distribution.
338 enumerator MEMCACHED_DISTRIBUTION_RANDOM
340 Distribute keys by rand(3) modulo number of servers.
341 enumerator MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA_SPY
343 Unweighted consistent key distribution compatible with
344 the SPY client.
345 enumerator MEMCACHED_DISTRIBUTION_CONSISTENT_WEIGHTED
347 Weighted consistent key distribution.
348 enumerator MEMCACHED_DISTRIBUTION_VIRTUAL_BUCKET
350 Consistent key distribution by virtual buckets.
351
353 libmemcached behavior can be modified by using
354 memcached_behavior_set(). Default behavior is the library strives to
355 be quick and accurate. Some behavior, while being faster, can also re‐
356 sult in not entirely accurate behavior (for instance, memcached_set()
357 will always respond with MEMCACHED_SUCCESS).
358 memcached_behavior_get() takes a behavior flag and returns whether or
360 not that behavior is currently enabled in the client.
361 memcached_behavior_set() changes the value of a particular option of
363 the client. It takes both a flag and a value. For simple on or off op‐
364 tions you just need to pass in a value of 1. Calls to
365 memcached_behavior_set() will flush and reset all connections.
366
368 memcached_behavior_get() returns either the current value of the key,
369 or 0 or 1 on simple flag behaviors (1 being enabled).
370 memcached_behavior_set() returns failure or success.
371
373 The data argument of memcached_behavior_set() was changed in version
374 0.17 from taking a pointer to data value, to taking a uin64_t.
375
377 memcached(1) setsockopt(3) libmemcached(3) memcached_strerror(3)
3781.1 Jul 20, 2023 MEMCACHED_BEHAVIOR(3)