1..::docs::memcached_behavior(3) libmemcached ..::docs::memcached_behavior(3)
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6 memcached_behavior_get, memcached_behavior_set - Manipulate behavior
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9 C Client Library for memcached (libmemcached, -lmemcached)
10
12 #include <memcached.h>
13 uint64_t
15 memcached_behavior_get (memcached_st *ptr,
16 memcached_behavior flag);
17 memcached_return
19 memcached_behavior_set (memcached_st *ptr,
20 memcached_behavior flag,
21 uint64_t data);
22
24 libmemcached(3) behavior can be modified by use
25 memcached_behavior_set(). Default behavior is the library strives to
26 be quick and accurate. Some behavior, while being faster, can also
27 result in not entirely accurate behavior (for instance, memcached_set()
28 will 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
40 with a memcached server. Not all I/O operations are supported when
41 this behavior is enababled. The following operations will return
42 "MEMCACHED_NOT_SUPPORTED" when executed with the
43 MEMCACHED_BEHAVIOR_USE_UDP enabled: memcached_version(),
44 memcached_stat(), memcached_get(), memcached_get_by_key(),
45 memcached_mget(), memcached_mget_by_key(), memcached_fetch(),
46 memcached_fetch_result(), memcached_value_fetch().
47 All other operations are supported but are executed in a
49 'fire-and-forget' mode, in which once the client has executed the
50 operation, no attempt will be made to ensure the operation has been
51 received and acted on by the server.
52 libmemcached(3) does not allow TCP and UDP servers to be shared
54 within the same libmemached(3) client 'instance'. An attempt to add
55 a TCP server when this behavior is enabled will result in a
56 "MEMCACHED_INVALID_HOST_PROTOCOL", as will attempting to add a UDP
57 server when this behavior has not been enabled.
58 MEMCACHED_BEHAVIOR_NO_BLOCK
60 Causes libmemcached(3) to use asychronous IO. This is the fastest
61 transport available for storage functions.
62 MEMCACHED_BEHAVIOR_SND_TIMEOUT
64 This sets the microsecond behavior of the socket against the
65 SO_SNDTIMEO flag. In cases where you cannot use non-blocking IO
66 this will allow you to still have timeouts on the sending of data.
67 MEMCACHED_BEHAVIOR_RCV_TIMEOUT
69 This sets the microsecond behavior of the socket against the
70 SO_RCVTIMEO flag. In cases where you cannot use non-blocking IO
71 this will allow you to still have timeouts on the reading of data.
72 MEMCACHED_BEHAVIOR_TCP_NODELAY
74 Turns on the no-delay feature for connecting sockets (may be faster
75 in some environments).
76 MEMCACHED_BEHAVIOR_HASH
78 Makes the default hashing algorithm for keys use MD5. The value can
79 be set to either MEMCACHED_HASH_DEFAULT, MEMCACHED_HASH_MD5,
80 MEMCACHED_HASH_CRC, MEMCACHED_HASH_FNV1_64,
81 MEMCACHED_HASH_FNV1A_64, MEMCACHED_HASH_FNV1_32,
82 MEMCACHED_HASH_FNV1A_32, MEMCACHED_HASH_JENKINS,
83 MEMCACHED_HASH_HSIEH, and MEMCACHED_HASH_MURMUR. Each hash has
84 it's advantages and it's weaknesses. If you dont know or dont care,
85 just go with the default. Support for MEMCACHED_HASH_HSIEH is a
86 compile time option that is disabled by default. To enable support
87 for this hashing algorithm, configure and build libmemcached with
88 the --enable-hash_hsieh.
89 MEMCACHED_BEHAVIOR_DISTRIBUTION
91 Using this you can enable different means of distributing values to
92 servers. The default method is MEMCACHED_DISTRIBUTION_MODULA. You
93 can enable consistent hashing by setting
94 MEMCACHED_DISTRIBUTION_CONSISTENT. Consistent hashing delivers
95 better distribution and allows servers to be added to the cluster
96 with minimal cache losses. Currently
97 MEMCACHED_DISTRIBUTION_CONSISTENT is an alias for the value
98 MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA.
99 MEMCACHED_BEHAVIOR_CACHE_LOOKUPS
101 Memcached can cache named lookups so that DNS lookups are made only
102 once.
103 MEMCACHED_BEHAVIOR_SUPPORT_CAS
105 Support CAS operations (this is not enabled by default at this
106 point in the server since it imposes a slight performance penalty).
107 MEMCACHED_BEHAVIOR_KETAMA
109 Sets the default distribution to
110 MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA and the hash to
111 MEMCACHED_HASH_MD5.
112 MEMCACHED_BEHAVIOR_KETAMA_WEIGHTED
114 Sets the default distribution to
115 MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA with the weighted support.
116 and the hash to MEMCACHED_HASH_MD5.
117 MEMCACHED_BEHAVIOR_KETAMA_HASH
119 Sets the hashing algorithm for host mapping on continuum. The value
120 can be set to either MEMCACHED_HASH_DEFAULT, MEMCACHED_HASH_MD5,
121 MEMCACHED_HASH_CRC, MEMCACHED_HASH_FNV1_64,
122 MEMCACHED_HASH_FNV1A_64, MEMCACHED_HASH_FNV1_32, and
123 MEMCACHED_HASH_FNV1A_32.
124 MEMCACHED_BEHAVIOR_POLL_TIMEOUT
126 Modify the timeout value that is used by poll(). The default value
127 is -1. An signed int pointer must be passed to
128 memcached_behavior_set() to change this value. For
129 memcached_behavior_get() a signed int value will be cast and
130 returned as the unsigned long long.
131 MEMCACHED_BEHAVIOR_USER_DATA
133 This allows you to store a pointer to a specifc piece of data. This
134 can be retrieved from inside of memcached_fetch_execute(). Cloning
135 a memcached_st
136 will copy the pointer to the clone. This was deprecated in 0.14 in
138 favor of memcached_callback_set(3). This will be removed in 0.15.
139 MEMCACHED_BEHAVIOR_BUFFER_REQUESTS
141 Enabling buffered IO causes commands to "buffer" instead of being
142 sent. Any action that gets data causes this buffer to be be sent to
143 the remote connection. Quiting the connection or closing down the
144 connection will also cause the buffered data to be pushed to the
145 remote connection.
146 MEMCACHED_BEHAVIOR_VERIFY_KEY
148 Enabling this will cause libmemcached(3) to test all keys to verify
149 that they are valid keys.
150 MEMCACHED_BEHAVIOR_SORT_HOSTS
152 Enabling this will cause hosts that are added to be placed in the
153 host list in sorted order. This will defeat consisten hashing.
154 MEMCACHED_BEHAVIOR_CONNECT_TIMEOUT
156 In non-blocking mode this changes the value of the timeout during
157 socket connection.
158 MEMCACHED_BEHAVIOR_BINARY_PROTOCOL
160 Enable the use of the binary protocol. Please note that you cannot
161 toggle this flag on an open connection.
162 MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT
164 Set this value to enable the server be removed after continuous
165 MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT times connection failure.
166 MEMCACHED_BEHAVIOR_IO_MSG_WATERMARK
168 Set this value to tune the number of messages that may be sent
169 before libmemcached should start to automatically drain the input
170 queue. Setting this value to high, may cause libmemcached to
171 deadlock (trying to send data, but the send will block because the
172 input buffer in the kernel is full).
173 MEMCACHED_BEHAVIOR_IO_BYTES_WATERMARK
175 Set this value to tune the number of bytes that may be sent before
176 libmemcached should start to automatically drain the input queue
177 (need at least 10 IO requests sent without reading the input
178 buffer). Setting this value to high, may cause libmemcached to
179 deadlock (trying to send data, but the send will block because the
180 input buffer in the kernel is full).
181 MEMCACHED_BEHAVIOR_IO_KEY_PREFETCH
183 The binary protocol works a bit different than the textual protocol
184 in that a multiget is implemented as a pipe of single get-
185 operations which are sent to the server in a chunk. If you are
186 using large multigets from your application, you may improve the
187 latency of the gets by setting this value so you send out the first
188 chunk of requests when you hit the specified limit. It allows the
189 servers to start processing the requests to send the data back
190 while the rest of the requests are created and sent to the server.
191 MEMCACHED_BEHAVIOR_NOREPLY
193 Set this value to specify that you really don't care about the
194 result from your storage commands (set, add, replace, append,
195 prepend).
196 MEMCACHED_BEHAVIOR_NUMBER_OF_REPLICAS
198 If you just want "a poor mans HA", you may specify the numbers of
199 replicas libmemcached should store of each item (on different
200 servers). This replication does not dedicate certain memcached
201 servers to store the replicas in, but instead it will store the
202 replicas together with all of the other objects (on the 'n' next
203 servers specified in your server list).
204
206 memcached_behavior_get() returns either the current value of the get,
207 or 0 or 1 on simple flag behaviors (1 being enabled).
208 memcached_behavior_set() returns failure or success.
209
211 memcached_behavior_set() in version .17 was changed from taking a
212 pointer to data value, to taking a uin64_t.
213
215 To find out more information please check:
216 <http://tangent.org/552/libmemcached.html>
217
219 Brian Aker, <brian@tangent.org>
220
222 memcached(1) libmemcached(3) memcached_strerror(3)
223 2009-06-27 ..::docs::memcached_behavior(3)