git.m6w6.name Git - m6w6/libmemcached/blob - 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