Style cleanup
[m6w6/libmemcached] / docs / memcached_behavior.rst
1 ================================
2 Modifying how the driver behaves
3 ================================
4
5
6 Manipulate the behavior of a memcached_st structure.
7
8 .. index:: object: memcached_st
9
10
11 --------
12 SYNOPSIS
13 --------
14
15
16 #include <libmemcached/memcached.h>
17
18 .. c:function:: uint64_t memcached_behavior_get (memcached_st *ptr, memcached_behavior flag);
19
20 .. c:function:: memcached_return_t memcached_behavior_set (memcached_st *ptr, memcached_behavior flag, uint64_t data);
21
22 Compile and link with -lmemcached
23
24
25 -----------
26 DESCRIPTION
27 -----------
28
29 :manpage:`libmemcached(3)` behavior can be modified by using :c:func:`memcached_behavior_set()`. Default behavior is the library strives to be quick and
30 accurate. Some behavior, while being faster, can also result in not entirely
31 accurate behavior (for instance, :c:func:`memcached_set()` will always respond
32 with :c:type:`MEMCACHED_SUCCESS`).
33
34 :c:func:`memcached_behavior_get()` takes a behavior flag and returns whether or not that behavior is currently enabled in the client.
35
36 :c:func:`memcached_behavior_set()` changes the value of a particular option
37 of the client. It takes both a flag (listed below) and a value. For simple
38 on or off options you just need to pass in a value of 1. Calls to
39 :c:func:`memcached_behavior_set()` will flush and reset all connections.
40
41
42 .. c:type:: MEMCACHED_BEHAVIOR_USE_UDP
43
44 Causes :manpage:`libmemcached(3)` to use the UDP transport when communicating
45 with a memcached server. Not all I/O operations are testsed
46 when this behavior is enababled. The following operations will return
47 :c:type:`MEMCACHED_NOT_SUPPORTED` when executed with the :c:type:`MEMCACHED_BEHAVIOR_USE_UDP` enabled: :c:func:`memcached_version()`, :c:func:`memcached_stat()`, :c:func:`memcached_get()`, :c:func:`memcached_get_by_key()`, :c:func:`memcached_mget()`, :c:func:`memcached_mget_by_key()`, :c:func:`memcached_fetch()`, :c:func:`memcached_fetch_result()`, :c:func:`memcached_value_fetch()`.
48
49 All other operations are testsed but are executed in a 'fire-and-forget'
50 mode, in which once the client has executed the operation, no attempt
51 will be made to ensure the operation has been received and acted on by the
52 server.
53
54 :manpage:`libmemcached(3)` does not allow TCP and UDP servers to be shared
55 within the same libmemached(3) client 'instance'. An attempt to add a TCP
56 server when this behavior is enabled will result in a :c:type:`MEMCACHED_INVALID_HOST_PROTOCOL`, as will attempting to add a UDP server when this behavior has
57 not been enabled.
58
59
60
61 .. c:type:: MEMCACHED_BEHAVIOR_NO_BLOCK
62
63 Causes :manpage:`libmemcached(3)` to use asychronous IO. This is the fastest
64 transport available for storage functions.
65
66
67 .. c:type:: MEMCACHED_BEHAVIOR_SND_TIMEOUT
68
69 This sets the microsecond behavior of the socket against the SO_SNDTIMEO flag. In cases where you cannot use non-blocking IO this will allow you to still have timeouts on the sending of data.
70
71
72 .. c:type:: MEMCACHED_BEHAVIOR_RCV_TIMEOUT
73
74 This sets the microsecond behavior of the socket against the SO_RCVTIMEO flag.
75
76 In cases where you cannot use non-blocking IO this will allow you to still have timeouts on the reading of data.
77
78
79
80 .. c:type:: MEMCACHED_BEHAVIOR_TCP_NODELAY
81
82 Turns on the no-delay feature for connecting sockets (may be faster in some
83 environments).
84
85
86
87 .. c:type:: MEMCACHED_BEHAVIOR_HASH
88
89 Makes the default hashing algorithm for keys use MD5. The value can be set to either :c:type:`MEMCACHED_HASH_DEFAULT`, :c:type:`MEMCACHED_HASH_MD5`, :c:type:`MEMCACHED_HASH_CRC`, :c:type:`MEMCACHED_HASH_FNV1_64`, :c:type:`MEMCACHED_HASH_FNV1A_64`, :c:type:`MEMCACHED_HASH_FNV1_32`, :c:type:`MEMCACHED_HASH_FNV1A_32`, :c:type:`MEMCACHED_HASH_JENKINS`, :c:type:`MEMCACHED_HASH_HSIEH`, and :c:type:`MEMCACHED_HASH_MURMUR`.
90
91 Each hash has it's advantages and it's weaknesses. If you don't know or don't
92 care, just go with the default.
93
94 Support for :c:type:`MEMCACHED_HASH_HSIEH` is a compile time option that is disabled by default. To enable tests for this hashing algorithm, configure and build libmemcached with the --enable-hash_hsieh.
95
96
97
98 .. c:type:: MEMCACHED_BEHAVIOR_DISTRIBUTION
99
100 Using this you can enable different means of distributing values to servers.
101
102 The default method is MEMCACHED_DISTRIBUTION_MODULA. 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.
103
104 .. c:type:: MEMCACHED_BEHAVIOR_CACHE_LOOKUPS
105 .. deprecated:: 0.46(?)
106 DNS lookups are now always cached until an error occurs with the server.
107
108 Memcached can cache named lookups so that DNS lookups are made only once.
109
110 .. c:type:: MEMCACHED_BEHAVIOR_SUPPORT_CAS
111
112 Support CAS operations (this is not enabled by default at this point in the server since it imposes a slight performance penalty).
113
114
115 .. c:type:: MEMCACHED_BEHAVIOR_KETAMA
116
117 Sets the default distribution to MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA and the hash to MEMCACHED_HASH_MD5.
118
119
120 .. c:type:: MEMCACHED_BEHAVIOR_KETAMA_WEIGHTED
121
122 Sets the default distribution to MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA with the weighted tests. and the hash to MEMCACHED_HASH_MD5.
123
124 .. c:type:: MEMCACHED_BEHAVIOR_KETAMA_HASH
125
126 Sets the hashing algorithm for host mapping on continuum. The value can be set to either MEMCACHED_HASH_DEFAULT, MEMCACHED_HASH_MD5, MEMCACHED_HASH_CRC, MEMCACHED_HASH_FNV1_64, MEMCACHED_HASH_FNV1A_64, MEMCACHED_HASH_FNV1_32, and MEMCACHED_HASH_FNV1A_32.
127
128 .. c:type:: MEMCACHED_BEHAVIOR_KETAMA_COMPAT
129
130 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.
131
132 .. c:type:: MEMCACHED_BEHAVIOR_POLL_TIMEOUT
133
134 Modify the timeout value that is used by poll(). The default value is -1. An signed int pointer must be passed to memcached_behavior_set() to change this value. For memcached_behavior_get() a signed int value will be cast and returned as the unsigned long long.
135
136 .. c:type:: MEMCACHED_BEHAVIOR_USER_DATA
137 .. deprecated:: < 0.30
138
139 .. c:type:: MEMCACHED_BEHAVIOR_BUFFER_REQUESTS
140
141 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.
142
143
144 .. c:type:: MEMCACHED_BEHAVIOR_VERIFY_KEY
145
146 Enabling this will cause :manpage:`libmemcached(3)` to test all keys to verify that they are valid keys.
147
148
149
150 .. c:type:: MEMCACHED_BEHAVIOR_SORT_HOSTS
151
152 Enabling this will cause hosts that are added to be placed in the host list in sorted order. This will defeat consisten hashing.
153
154
155
156 .. c:type:: MEMCACHED_BEHAVIOR_CONNECT_TIMEOUT
157
158 In non-blocking mode this changes the value of the timeout during socket connection.
159
160
161
162 .. c:type:: MEMCACHED_BEHAVIOR_BINARY_PROTOCOL
163
164 Enable the use of the binary protocol. Please note that you cannot toggle this flag on an open connection.
165
166
167
168 .. c:type:: MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT
169
170 Set this value to enable the server be removed after continuous MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT times connection failure.
171
172
173
174 .. c:type:: MEMCACHED_BEHAVIOR_IO_MSG_WATERMARK
175
176 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).
177
178
179
180 .. c:type:: MEMCACHED_BEHAVIOR_IO_BYTES_WATERMARK
181
182 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).
183
184
185
186 .. c:type:: MEMCACHED_BEHAVIOR_IO_KEY_PREFETCH
187
188 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.
189
190
191
192 .. c:type:: MEMCACHED_BEHAVIOR_NOREPLY
193
194 Set this value to specify that you really don't care about the result from your storage commands (set, add, replace, append, prepend).
195
196
197
198 .. c:type:: MEMCACHED_BEHAVIOR_NUMBER_OF_REPLICAS
199
200 If you just want "a poor mans HA", you may specify the numbers 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).
201
202
203
204 .. c:type:: MEMCACHED_BEHAVIOR_RANDOMIZE_REPLICA_READ
205
206 Allows randomizing the replica reads starting point. Normally the read is done from primary server and in case of miss the read is done from primary + 1, then primary + 2 all the way to 'n' replicas. If this option is set on the starting point of the replica reads is randomized between the servers. This allows distributing read load to multiple servers with the expense of more write traffic.
207
208
209
210 .. c:type:: MEMCACHED_BEHAVIOR_CORK
211
212 This open has been deprecated with the behavior now built and used appropriately on selected platforms.
213
214
215 .. c:type:: MEMCACHED_BEHAVIOR_KEEPALIVE
216
217 Enable TCP_KEEPALIVE behavior.
218
219
220
221 .. c:type:: MEMCACHED_BEHAVIOR_KEEPALIVE_IDLE
222
223 Specify time, in seconds, to mark a connection as idle. This is only available as an option Linux.
224
225
226 .. c:type:: MEMCACHED_BEHAVIOR_SOCKET_SEND_SIZE
227
228 Find the current size of SO_SNDBUF. A value of 0 means either an error occured or no hosts were available. It is safe to assume system default if this occurs. If an error occurs you can checked the last cached errno statement to find the specific error.
229
230
231 .. c:type:: MEMCACHED_BEHAVIOR_SOCKET_RECV_SIZE
232
233 Find the current size of SO_RCVBUF. A value of 0 means either an error occured or no hosts were available. It is safe to assume system default if this occurs. If an error occurs you can checked the last cached errno statement to find the specific error.
234
235
236 .. c:type:: MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT
237 .. deprecated:: 0.48
238 See :c:type:`MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS`
239
240 This number of times a host can have an error before it is disabled.
241
242
243 .. c:type:: MEMCACHED_BEHAVIOR_AUTO_EJECT_HOSTS
244 .. deprecated:: 0.48
245 See :c:type:`MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS`
246
247 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.
248
249 .. c:type:: MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS
250
251 If enabled any hosts which have been flagged as disabled will be removed from the list of servers in the memcached_st structure.
252
253 .. c:type:: MEMCACHED_BEHAVIOR_RETRY_TIMEOUT
254
255 When enabled a host which is problematic will only be checked for usage based on the amount of time set by this behavior.
256
257
258 .. c:type:: MEMCACHED_BEHAVIOR_HASH_WITH_PREFIX_KEY
259
260 When enabled the prefix key will be added to the key when determining server
261 by hash. See :c:type:`MEMCACHED_CALLBACK_NAMESPACE` for additional
262 information.
263
264
265
266
267 ------
268 RETURN
269 ------
270
271
272 memcached_behavior_get() returns either the current value of the get, or 0
273 or 1 on simple flag behaviors (1 being enabled). memcached_behavior_set()
274 returns failure or success.
275
276
277 -----
278 NOTES
279 -----
280
281
282 memcached_behavior_set() in version .17 was changed from taking a pointer
283 to data value, to taking a uin64_t.
284
285
286 ----
287 HOME
288 ----
289
290
291 To find out more information please check:
292 `http://libmemcached.org/ <http://libmemcached.org/>`_
293
294
295
296 --------
297 SEE ALSO
298 --------
299
300
301 :manpage:`memcached(1)` :manpage:`libmemcached(3)` :manpage:`memcached_strerror(3)`