1MEMCACHED_BEHAVIOR_GET(3) libmemcached MEMCACHED_BEHAVIOR_GET(3)
2
6 memcached_behavior_get - libmemcached Documentation
7 Manipulate the behavior of a memcached_st structure.
9
11 #include <libmemcached/memcached.h>
12 memcached_behavior_t
14 uint64_t memcached_behavior_get(memcached_st *ptr,
16 memcached_behavior_t flag)
17 memcached_return_t memcached_behavior_set(memcached_st *ptr,
19 memcached_behavior_t flag, uint64_t data)
20 Compile and link with -lmemcached
22
24 libmemcached(3) behavior can be modified by using
25 memcached_behavior_set(). Default behavior is the library strives to be
26 quick and accurate. Some behavior, while being faster, can also result
27 in not entirely accurate behavior (for instance, memcached_set() will
28 always respond with MEMCACHED_SUCCESS).
29 memcached_behavior_get() takes a behavior flag and returns whether or
31 not that behavior is currently enabled in the client.
32 memcached_behavior_set() changes the value of a particular option of
34 the client. It takes both a flag (listed below) and a value. For simple
35 on or off options you just need to pass in a value of 1. Calls to
36 memcached_behavior_set() will flush and reset all connections.
37 MEMCACHED_BEHAVIOR_USE_UDP
39 Causes libmemcached(3) to use the UDP transport when communicating with
41 a memcached server. Not all I/O operations are testsed when this behav‐
42 ior is enababled. The following operations will return MEM‐
43 CACHED_NOT_SUPPORTED when executed with the MEMCACHED_BEHAVIOR_USE_UDP
44 enabled: memcached_version(), memcached_stat(), memcached_get(), mem‐
45 cached_get_by_key(), memcached_mget(), memcached_mget_by_key(), mem‐
46 cached_fetch(), memcached_fetch_result(), memcached_fetch_execute().
47 All other operations are testsed but are executed in a 'fire-and-for‐
49 get' mode, in which once the client has executed the operation, no
50 attempt will be made to ensure the operation has been received and
51 acted on by the server.
52 libmemcached(3) does not allow TCP and UDP servers to be shared within
54 the same libmemached(3) client 'instance'. An attempt to add a TCP
55 server when this behavior is enabled will result in a MEM‐
56 CACHED_INVALID_HOST_PROTOCOL, as will attempting to add a UDP server
57 when this behavior has not been enabled.
58 MEMCACHED_BEHAVIOR_NO_BLOCK
60 Causes libmemcached(3) to use asychronous IO. This is the fastest
62 transport available for storage functions.
63 MEMCACHED_BEHAVIOR_SND_TIMEOUT
65 This sets the microsecond behavior of the socket against the SO_SND‐
67 TIMEO flag. In cases where you cannot use non-blocking IO this will
68 allow you to still have timeouts on the sending of data.
69 MEMCACHED_BEHAVIOR_RCV_TIMEOUT
71 This sets the microsecond behavior of the socket against the SO_RCV‐
73 TIMEO flag.
74 In cases where you cannot use non-blocking IO this will allow you to
76 still have timeouts on the reading of data.
77 MEMCACHED_BEHAVIOR_TCP_NODELAY
79 Turns on the no-delay feature for connecting sockets (may be faster in
81 some environments).
82 MEMCACHED_BEHAVIOR_HASH
84 Makes the default hashing algorithm for keys use MD5. The value can be
86 set to either MEMCACHED_HASH_DEFAULT, MEMCACHED_HASH_MD5, MEM‐
87 CACHED_HASH_CRC, MEMCACHED_HASH_FNV1_64, MEMCACHED_HASH_FNV1A_64, MEM‐
88 CACHED_HASH_FNV1_32, MEMCACHED_HASH_FNV1A_32, MEMCACHED_HASH_JENKINS,
89 MEMCACHED_HASH_HSIEH, and MEMCACHED_HASH_MURMUR.
90 Each hash has it's advantages and it's weaknesses. If you don't know or
92 don't care, just go with the default.
93 Support for MEMCACHED_HASH_HSIEH is a compile time option that is dis‐
95 abled by default. To enable tests for this hashing algorithm, configure
96 and build libmemcached with the --enable-hash_hsieh.
97 MEMCACHED_BEHAVIOR_DISTRIBUTION
99 Using this you can enable different means of distributing values to
101 servers.
102 The default method is MEMCACHED_DISTRIBUTION_MODULA. You can enable
104 consistent hashing by setting MEMCACHED_DISTRIBUTION_CONSISTENT. Con‐
105 sistent hashing delivers better distribution and allows servers to be
106 added to the cluster with minimal cache losses. Currently MEM‐
107 CACHED_DISTRIBUTION_CONSISTENT is an alias for the value MEMCACHED_DIS‐
108 TRIBUTION_CONSISTENT_KETAMA.
109 MEMCACHED_BEHAVIOR_CACHE_LOOKUPS
111 Deprecated since version 0.46(?): DNS lookups are now always cached
113 until an error occurs with the server.
114 Memcached can cache named lookups so that DNS lookups are made only
116 once.
117 MEMCACHED_BEHAVIOR_SUPPORT_CAS
120 Support CAS operations (this is not enabled by default at this point in
122 the server since it imposes a slight performance penalty).
123 MEMCACHED_BEHAVIOR_KETAMA
125 Sets the default distribution to MEMCACHED_DISTRIBUTION_CONSIS‐
127 TENT_KETAMA and the hash to MEMCACHED_HASH_MD5.
128 MEMCACHED_BEHAVIOR_KETAMA_WEIGHTED
130 Sets the default distribution to MEMCACHED_DISTRIBUTION_CONSIS‐
131 TENT_KETAMA with the weighted tests. and the hash to MEM‐
132 CACHED_HASH_MD5.
133 MEMCACHED_BEHAVIOR_KETAMA_HASH
135 Sets the hashing algorithm for host mapping on continuum. The value can
137 be set to either MEMCACHED_HASH_DEFAULT, MEMCACHED_HASH_MD5, MEM‐
138 CACHED_HASH_CRC, MEMCACHED_HASH_FNV1_64, MEMCACHED_HASH_FNV1A_64, MEM‐
139 CACHED_HASH_FNV1_32, and MEMCACHED_HASH_FNV1A_32.
140 MEMCACHED_BEHAVIOR_KETAMA_COMPAT
142 Sets the compatibility mode. The value can be set to either MEM‐
144 CACHED_KETAMA_COMPAT_LIBMEMCACHED (this is the default) or MEM‐
145 CACHED_KETAMA_COMPAT_SPY to be compatible with the SPY Memcached client
146 for Java.
147 MEMCACHED_BEHAVIOR_POLL_TIMEOUT
149 Modify the timeout value that is used by poll. The default value is -1.
151 An signed int must be passed to memcached_behavior_set to change this
152 value (this requires casting). For memcached_behavior_get a signed int
153 value will be cast and returned as the unsigned long long.
154 MEMCACHED_BEHAVIOR_USER_DATA
156 Deprecated since version <: 0.30
158 MEMCACHED_BEHAVIOR_BUFFER_REQUESTS
160 Enabling buffered IO causes commands to "buffer" instead of being sent.
162 Any action that gets data causes this buffer to be be sent to the
163 remote connection. Quiting the connection or closing down the connec‐
164 tion will also cause the buffered data to be pushed to the remote con‐
165 nection.
166 MEMCACHED_BEHAVIOR_VERIFY_KEY
168 Enabling this will cause libmemcached(3) to test all keys to verify
170 that they are valid keys.
171 MEMCACHED_BEHAVIOR_SORT_HOSTS
173 Enabling this will cause hosts that are added to be placed in the host
175 list in sorted order. This will defeat consisten hashing.
176 MEMCACHED_BEHAVIOR_CONNECT_TIMEOUT
178 In non-blocking mode this changes the value of the timeout during
180 socket connection in milliseconds. Specifying -1 means an infinite
181 time‐out.
182 MEMCACHED_BEHAVIOR_BINARY_PROTOCOL
184 Enable the use of the binary protocol. Please note that you cannot tog‐
186 gle this flag on an open connection.
187 MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT
189 Set this value to enable the server be removed after continuous MEM‐
191 CACHED_BEHAVIOR_SERVER_FAILURE_LIMIT times connection failure.
192 MEMCACHED_BEHAVIOR_IO_MSG_WATERMARK
194 Set this value to tune the number of messages that may be sent before
196 libmemcached should start to automatically drain the input queue. Set‐
197 ting this value to high, may cause libmemcached to deadlock (trying to
198 send data, but the send will block because the input buffer in the ker‐
199 nel is full).
200 MEMCACHED_BEHAVIOR_IO_BYTES_WATERMARK
202 Set this value to tune the number of bytes that may be sent before lib‐
204 memcached should start to automatically drain the input queue (need at
205 least 10 IO requests sent without reading the input buffer). Setting
206 this value to high, may cause libmemcached to deadlock (trying to send
207 data, but the send will block because the input buffer in the kernel is
208 full).
209 MEMCACHED_BEHAVIOR_IO_KEY_PREFETCH
211 The binary protocol works a bit different than the textual protocol in
213 that a multiget is implemented as a pipe of single get-operations which
214 are sent to the server in a chunk. If you are using large multigets
215 from your application, you may improve the latency of the gets by set‐
216 ting this value so you send out the first chunk of requests when you
217 hit the specified limit. It allows the servers to start processing the
218 requests to send the data back while the rest of the requests are cre‐
219 ated and sent to the server.
220 MEMCACHED_BEHAVIOR_NOREPLY
222 Set this value to specify that you really don't care about the result
224 from your storage commands (set, add, replace, append, prepend).
225 MEMCACHED_BEHAVIOR_NUMBER_OF_REPLICAS
227 If you just want "a poor mans HA", you may specify the numbers of
229 replicas libmemcached should store of each item (on different servers).
230 This replication does not dedicate certain memcached servers to store
231 the replicas in, but instead it will store the replicas together with
232 all of the other objects (on the 'n' next servers specified in your
233 server list).
234 MEMCACHED_BEHAVIOR_RANDOMIZE_REPLICA_READ
236 Allows randomizing the replica reads starting point. Normally the read
238 is done from primary server and in case of miss the read is done from
239 primary + 1, then primary + 2 all the way to 'n' replicas. If this
240 option is set on the starting point of the replica reads is randomized
241 between the servers. This allows distributing read load to multiple
242 servers with the expense of more write traffic.
243 MEMCACHED_BEHAVIOR_CORK
245 This open has been deprecated with the behavior now built and used
247 appropriately on selected platforms.
248 MEMCACHED_BEHAVIOR_KEEPALIVE
250 Enable TCP_KEEPALIVE behavior.
252 MEMCACHED_BEHAVIOR_KEEPALIVE_IDLE
254 Specify time, in seconds, to mark a connection as idle. This is only
256 available as an option Linux.
257 MEMCACHED_BEHAVIOR_SOCKET_SEND_SIZE
259 Find the current size of SO_SNDBUF. A value of 0 means either an error
261 occured or no hosts were available. It is safe to assume system default
262 if this occurs. If an error occurs you can checked the last cached
263 errno statement to find the specific error.
264 MEMCACHED_BEHAVIOR_SOCKET_RECV_SIZE
266 Find the current size of SO_RCVBUF. A value of 0 means either an error
268 occured or no hosts were available. It is safe to assume system default
269 if this occurs. If an error occurs you can checked the last cached
270 errno statement to find the specific error.
271 MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT
273 Deprecated since version 0.48: See
275 MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS
276 This number of times a host can have an error before it is disabled.
278 MEMCACHED_BEHAVIOR_AUTO_EJECT_HOSTS
281 Deprecated since version 0.48: See
283 MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS
284 If enabled any hosts which have been flagged as disabled will be
286 removed from the list of servers in the memcached_st structure. This
287 must be used in combination with MEMCACHED_BEHAVIOR_SERVER_FAIL‐
288 URE_LIMIT.
289 MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS
292 If enabled any hosts which have been flagged as disabled will be
293 removed from the list of servers in the memcached_st structure.
294 MEMCACHED_BEHAVIOR_RETRY_TIMEOUT
296 When enabled a host which is problematic will only be checked for usage
298 based on the amount of time set by this behavior. The value is in sec‐
299 onds.
300 MEMCACHED_BEHAVIOR_HASH_WITH_PREFIX_KEY
302 When enabled the prefix key will be added to the key when determining
304 server by hash. See MEMCACHED_CALLBACK_NAMESPACE for additional infor‐
305 mation.
306
308 memcached_behavior_get returns either the current value of the get, or
309 0 or 1 on simple flag behaviors (1 being enabled). memcached_behav‐
310 ior_set returns failure or success.
311
313 memcached_behavior_set in version .17 was changed from taking a pointer
314 to data value, to taking a uin64_t.
315
317 To find out more information please check: http://libmemcached.org/
318
320 memcached(1) libmemcached(3) memcached_strerror(3)
321
323 Brian Aker
324
326 2011-2013, Brian Aker DataDifferential, http://datadifferential.com/
3271.0.16 January 31, 2013 MEMCACHED_BEHAVIOR_GET(3)