Include config.h before any system header to avoid problems with FILE_OFFSET_BITS...
[m6w6/libmemcached] / docs / memcached_behavior.pod
1 =head1 NAME
2
3 memcached_behavior_get, memcached_behavior_set - Manipulate behavior
4
5 =head1 LIBRARY
6
7 C Client Library for memcached (libmemcached, -lmemcached)
8
9 =head1 SYNOPSIS
10
11 #include <memcached.h>
12
13 uint64_t
14 memcached_behavior_get (memcached_st *ptr,
15 memcached_behavior flag);
16
17 memcached_return
18 memcached_behavior_set (memcached_st *ptr,
19 memcached_behavior flag,
20 uint64_t data);
21
22 =head1 DESCRIPTION
23
24 libmemcached(3) behavior can be modified by use memcached_behavior_set().
25 Default behavior is the library strives to be quick and accurate. Some
26 behavior, while being faster, can also result in not entirely accurate
27 behavior (for instance, memcached_set() will always respond with
28 C<MEMCACHED_SUCCESS>).
29
30 memcached_behavior_get() takes a behavior flag and returns whether or not
31 that behavior is currently enabled in the client.
32
33 memcached_behavior_set() changes the value of a particular option of the
34 client. It takes both a flag (listed below) and a value. For simple on or
35 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
38 =over 4
39
40 =item MEMCACHED_BEHAVIOR_USE_UDP
41
42 Causes libmemcached(3) to use the UDP transport when communicating
43 with a memcached server. Not all I/O operations are supported
44 when this behavior is enababled. The following operations will return
45 C<MEMCACHED_NOT_SUPPORTED> when executed with the MEMCACHED_BEHAVIOR_USE_UDP
46 enabled: memcached_version(), memcached_stat(), memcached_get(),
47 memcached_get_by_key(), memcached_mget(), memcached_mget_by_key(),
48 memcached_fetch(), memcached_fetch_result(), memcached_value_fetch().
49
50 All other operations are supported but are executed in a 'fire-and-forget'
51 mode, in which once the client has executed the operation, no attempt
52 will be made to ensure the operation has been received and acted on by the
53 server.
54
55 libmemcached(3) does not allow TCP and UDP servers to be shared within
56 the same libmemached(3) client 'instance'. An attempt to add a TCP server
57 when this behavior is enabled will result in a C<MEMCACHED_INVALID_HOST_PROTOCOL>,
58 as will attempting to add a UDP server when this behavior has not been enabled.
59
60 =item MEMCACHED_BEHAVIOR_NO_BLOCK
61
62 Causes libmemcached(3) to use asychronous IO. This is the fastest transport
63 available for storage functions.
64
65 =item MEMCACHED_BEHAVIOR_SND_TIMEOUT
66
67 This sets the microsecond behavior of the socket against the SO_SNDTIMEO flag.
68 In cases where you cannot use non-blocking IO this will allow you to still have
69 timeouts on the sending of data.
70
71 =item MEMCACHED_BEHAVIOR_RCV_TIMEOUT
72
73 This sets the microsecond behavior of the socket against the SO_RCVTIMEO flag.
74 In cases where you cannot use non-blocking IO this will allow you to still have
75 timeouts on the reading of data.
76
77 =item MEMCACHED_BEHAVIOR_TCP_NODELAY
78
79 Turns on the no-delay feature for connecting sockets (may be faster in some
80 environments).
81
82 =item MEMCACHED_BEHAVIOR_HASH
83
84 Makes the default hashing algorithm for keys use MD5. The value can be set
85 to either MEMCACHED_HASH_DEFAULT, MEMCACHED_HASH_MD5, MEMCACHED_HASH_CRC, MEMCACHED_HASH_FNV1_64, MEMCACHED_HASH_FNV1A_64, MEMCACHED_HASH_FNV1_32, MEMCACHED_HASH_FNV1A_32, MEMCACHED_HASH_JENKINS, MEMCACHED_HASH_HSIEH, and MEMCACHED_HASH_MURMUR.
86 Each hash has it's advantages and it's weaknesses. If you dont know or dont care, just go with the default.
87 Support for MEMCACHED_HASH_HSIEH is a compile time option that is disabled by default. To enable support for this hashing algorithm, configure and build libmemcached with the --enable-hash_hsieh.
88
89 =item MEMCACHED_BEHAVIOR_DISTRIBUTION
90
91 Using this you can enable different means of distributing values to servers.
92 The default method is MEMCACHED_DISTRIBUTION_MODULA. You can enable
93 consistent hashing by setting MEMCACHED_DISTRIBUTION_CONSISTENT.
94 Consistent hashing delivers better distribution and allows servers to be
95 added to the cluster with minimal cache losses. Currently
96 MEMCACHED_DISTRIBUTION_CONSISTENT is an alias for the value
97 MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA.
98
99 =item MEMCACHED_BEHAVIOR_CACHE_LOOKUPS
100
101 Memcached can cache named lookups so that DNS lookups are made only once.
102
103 =item MEMCACHED_BEHAVIOR_SUPPORT_CAS
104
105 Support CAS operations (this is not enabled by default at this point in the server since it imposes a slight performance penalty).
106
107 =item MEMCACHED_BEHAVIOR_KETAMA
108
109 Sets the default distribution to MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA
110 and the hash to MEMCACHED_HASH_MD5.
111
112 =item MEMCACHED_BEHAVIOR_KETAMA_WEIGHTED
113
114 Sets the default distribution to MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA with the weighted support.
115 and the hash to MEMCACHED_HASH_MD5.
116
117 =item MEMCACHED_BEHAVIOR_KETAMA_HASH
118
119 Sets the hashing algorithm for host mapping on continuum. The value can be set
120 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.
121
122 =item MEMCACHED_BEHAVIOR_POLL_TIMEOUT
123
124 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.
125
126 =item MEMCACHED_BEHAVIOR_USER_DATA
127
128 This allows you to store a pointer to a specifc piece of data. This can be
129 retrieved from inside of memcached_fetch_execute(). Cloning a memcached_st
130
131 will copy the pointer to the clone. This was deprecated in 0.14 in favor
132 of memcached_callback_set(3). This will be removed in 0.15.
133
134 =item MEMCACHED_BEHAVIOR_BUFFER_REQUESTS
135
136 Enabling buffered IO causes commands to "buffer" instead of being sent. Any
137 action that gets data causes this buffer to be be sent to the remote
138 connection. Quiting the connection or closing down the connection will also
139 cause the buffered data to be pushed to the remote connection.
140
141 =item MEMCACHED_BEHAVIOR_VERIFY_KEY
142
143 Enabling this will cause libmemcached(3) to test all keys to verify that they
144 are valid keys.
145
146 =item MEMCACHED_BEHAVIOR_SORT_HOSTS
147
148 Enabling this will cause hosts that are added to be placed in the host list in
149 sorted order. This will defeat consisten hashing.
150
151 =item MEMCACHED_BEHAVIOR_CONNECT_TIMEOUT
152
153 In non-blocking mode this changes the value of the timeout during socket
154 connection.
155
156 =item MEMCACHED_BEHAVIOR_BINARY_PROTOCOL
157
158 Enable the use of the binary protocol. Please note that you cannot toggle
159 this flag on an open connection.
160
161 =item MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT
162
163 Set this value to enable the server be removed after continuous MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT
164 times connection failure.
165
166 =item MEMCACHED_BEHAVIOR_IO_MSG_WATERMARK
167
168 Set this value to tune the number of messages that may be sent before
169 libmemcached should start to automatically drain the input queue. Setting
170 this value to high, may cause libmemcached to deadlock (trying to send data,
171 but the send will block because the input buffer in the kernel is full).
172
173 =item MEMCACHED_BEHAVIOR_IO_BYTES_WATERMARK
174
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 (need
177 at least 10 IO requests sent without reading the input buffer). Setting
178 this value to high, may cause libmemcached to deadlock (trying to send
179 data, but the send will block because the input buffer in the kernel is full).
180
181 =item MEMCACHED_BEHAVIOR_IO_KEY_PREFETCH
182
183 The binary protocol works a bit different than the textual protocol in
184 that a multiget is implemented as a pipe of single get-operations which
185 are sent to the server in a chunk. If you are using large multigets from
186 your application, you may improve the latency of the gets by setting
187 this value so you send out the first chunk of requests when you hit the
188 specified limit. It allows the servers to start processing the requests
189 to send the data back while the rest of the requests are created and
190 sent to the server.
191
192 =item MEMCACHED_BEHAVIOR_NOREPLY
193
194 Set this value to specify that you really don't care about the result
195 from your storage commands (set, add, replace, append, prepend).
196
197 =item MEMCACHED_BEHAVIOR_NUMBER_OF_REPLICAS
198
199 If you just want "a poor mans HA", you may specify the numbers of
200 replicas libmemcached should store of each item (on different servers).
201 This replication does not dedicate certain memcached servers to store the
202 replicas in, but instead it will store the replicas together with all of the
203 other objects (on the 'n' next servers specified in your server list).
204
205 =back
206
207 =head1 RETURN
208
209 memcached_behavior_get() returns either the current value of the get, or 0
210 or 1 on simple flag behaviors (1 being enabled). memcached_behavior_set()
211 returns failure or success.
212
213 =head1 NOTES
214
215 memcached_behavior_set() in version .17 was changed from taking a pointer
216 to data value, to taking a uin64_t.
217
218 =head1 HOME
219
220 To find out more information please check:
221 L<http://tangent.org/552/libmemcached.html>
222
223 =head1 AUTHOR
224
225 Brian Aker, E<lt>brian@tangent.orgE<gt>
226
227 =head1 SEE ALSO
228
229 memcached(1) libmemcached(3) memcached_strerror(3)
230
231 =cut
232