git.m6w6.name Git - m6w6/libmemcached/blob - docs/man/memcached_behavior.3

   1 .TH "MEMCACHED_BEHAVIOR" "3" "October 18, 2011" "1.01" "libmemcached"
   2 .SH NAME
   3 memcached_behavior \- libmemcached Documentation
   4 .
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  33 .sp
  34 Manipulate the behavior of a memcached_st structure.
  35 .SH SYNOPSIS
  36 .sp
  37 #include <libmemcached/memcached.h>
  38 .INDENT 0.0
  39 .TP
  40 .B uint64_t memcached_behavior_get (memcached_st *ptr, memcached_behavior flag);
  41 .UNINDENT
  42 .INDENT 0.0
  43 .TP
  44 .B memcached_return_t memcached_behavior_set (memcached_st *ptr, memcached_behavior flag, uint64_t data);
  45 .UNINDENT
  46 .sp
  47 Compile and link with \-lmemcached
  48 .SH DESCRIPTION
  49 .sp
  50 \fIlibmemcached(3)\fP behavior can be modified by using \fBmemcached_behavior_set()\fP. Default behavior is the library strives to be quick and
  51 accurate. Some behavior, while being faster, can also result in not entirely
  52 accurate behavior (for instance, \fBmemcached_set()\fP will always respond
  53 with \fBMEMCACHED_SUCCESS\fP).
  54 .sp
  55 \fBmemcached_behavior_get()\fP takes a behavior flag and returns whether or not that behavior is currently enabled in the client.
  56 .sp
  57 \fBmemcached_behavior_set()\fP changes the value of a particular option
  58 of the client. It takes both a flag (listed below) and a value. For simple
  59 on or off options you just need to pass in a value of 1. Calls to
  60 \fBmemcached_behavior_set()\fP will flush and reset all connections.
  61 .INDENT 0.0
  62 .TP
  63 .B MEMCACHED_BEHAVIOR_USE_UDP
  64 .UNINDENT
  65 .sp
  66 Causes \fIlibmemcached(3)\fP to use the UDP transport when communicating
  67 with a memcached server. Not all I/O operations are testsed
  68 when this behavior is enababled. The following operations will return
  69 \fBMEMCACHED_NOT_SUPPORTED\fP when executed with the \fI\%MEMCACHED_BEHAVIOR_USE_UDP\fP enabled: \fBmemcached_version()\fP, \fBmemcached_stat()\fP, \fBmemcached_get()\fP, \fBmemcached_get_by_key()\fP, \fBmemcached_mget()\fP, \fBmemcached_mget_by_key()\fP, \fBmemcached_fetch()\fP, \fBmemcached_fetch_result()\fP, \fBmemcached_value_fetch()\fP.
  70 .sp
  71 All other operations are testsed but are executed in a \(aqfire\-and\-forget\(aq
  72 mode, in which once the client has executed the operation, no attempt
  73 will be made to ensure the operation has been received and acted on by the
  74 server.
  75 .sp
  76 \fIlibmemcached(3)\fP does not allow TCP and UDP servers to be shared
  77 within the same libmemached(3) client \(aqinstance\(aq. An attempt to add a TCP
  78 server when this behavior is enabled will result in a \fBMEMCACHED_INVALID_HOST_PROTOCOL\fP, as will attempting to add a UDP server when this behavior has
  79 not been enabled.
  80 .INDENT 0.0
  81 .TP
  82 .B MEMCACHED_BEHAVIOR_NO_BLOCK
  83 .UNINDENT
  84 .sp
  85 Causes \fIlibmemcached(3)\fP to use asychronous IO. This is the fastest
  86 transport available for storage functions.
  87 .INDENT 0.0
  88 .TP
  89 .B MEMCACHED_BEHAVIOR_SND_TIMEOUT
  90 .UNINDENT
  91 .sp
  92 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.
  93 .INDENT 0.0
  94 .TP
  95 .B MEMCACHED_BEHAVIOR_RCV_TIMEOUT
  96 .UNINDENT
  97 .sp
  98 This sets the microsecond behavior of the socket against the SO_RCVTIMEO flag.
  99 .sp
 100 In cases where you cannot use non\-blocking IO this will allow you to still have timeouts on the reading of data.
 101 .INDENT 0.0
 102 .TP
 103 .B MEMCACHED_BEHAVIOR_TCP_NODELAY
 104 .UNINDENT
 105 .sp
 106 Turns on the no\-delay feature for connecting sockets (may be faster in some
 107 environments).
 108 .INDENT 0.0
 109 .TP
 110 .B MEMCACHED_BEHAVIOR_HASH
 111 .UNINDENT
 112 .sp
 113 Makes the default hashing algorithm for keys use MD5. The value can be set to either \fBMEMCACHED_HASH_DEFAULT\fP, \fBMEMCACHED_HASH_MD5\fP, \fBMEMCACHED_HASH_CRC\fP, \fBMEMCACHED_HASH_FNV1_64\fP, \fBMEMCACHED_HASH_FNV1A_64\fP, \fBMEMCACHED_HASH_FNV1_32\fP, \fBMEMCACHED_HASH_FNV1A_32\fP, \fBMEMCACHED_HASH_JENKINS\fP, \fBMEMCACHED_HASH_HSIEH\fP, and \fBMEMCACHED_HASH_MURMUR\fP.
 114 .sp
 115 Each hash has it\(aqs advantages and it\(aqs weaknesses. If you don\(aqt know or don\(aqt
 116 care, just go with the default.
 117 .sp
 118 Support for \fBMEMCACHED_HASH_HSIEH\fP 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.
 119 .INDENT 0.0
 120 .TP
 121 .B MEMCACHED_BEHAVIOR_DISTRIBUTION
 122 .UNINDENT
 123 .sp
 124 Using this you can enable different means of distributing values to servers.
 125 .sp
 126 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.
 127 .INDENT 0.0
 128 .TP
 129 .B MEMCACHED_BEHAVIOR_CACHE_LOOKUPS
 130 .UNINDENT
 131 .sp
 132 Deprecated since version 0.46(?): DNS lookups are now always cached until an error occurs with the server.
 133 .sp
 134 Memcached can cache named lookups so that DNS lookups are made only once.
 135
 136 .INDENT 0.0
 137 .TP
 138 .B MEMCACHED_BEHAVIOR_SUPPORT_CAS
 139 .UNINDENT
 140 .sp
 141 Support CAS operations (this is not enabled by default at this point in the server since it imposes a slight performance penalty).
 142 .INDENT 0.0
 143 .TP
 144 .B MEMCACHED_BEHAVIOR_KETAMA
 145 .UNINDENT
 146 .sp
 147 Sets the default distribution to MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA and the hash to MEMCACHED_HASH_MD5.
 148 .INDENT 0.0
 149 .TP
 150 .B MEMCACHED_BEHAVIOR_KETAMA_WEIGHTED
 151 .
 152 Sets the default distribution to MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA with the weighted tests.  and the hash to MEMCACHED_HASH_MD5.
 153 .UNINDENT
 154 .INDENT 0.0
 155 .TP
 156 .B MEMCACHED_BEHAVIOR_KETAMA_HASH
 157 .UNINDENT
 158 .sp
 159 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.
 160 .INDENT 0.0
 161 .TP
 162 .B MEMCACHED_BEHAVIOR_KETAMA_COMPAT
 163 .UNINDENT
 164 .sp
 165 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.
 166 .INDENT 0.0
 167 .TP
 168 .B MEMCACHED_BEHAVIOR_POLL_TIMEOUT
 169 .UNINDENT
 170 .sp
 171 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.
 172 .INDENT 0.0
 173 .TP
 174 .B MEMCACHED_BEHAVIOR_USER_DATA
 175 .UNINDENT
 176 .sp
 177 Deprecated since version <: 0.30
 178 .INDENT 0.0
 179 .TP
 180 .B MEMCACHED_BEHAVIOR_BUFFER_REQUESTS
 181 .UNINDENT
 182 .sp
 183 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.
 184 .INDENT 0.0
 185 .TP
 186 .B MEMCACHED_BEHAVIOR_VERIFY_KEY
 187 .UNINDENT
 188 .sp
 189 Enabling this will cause \fIlibmemcached(3)\fP to test all keys to verify that they are valid keys.
 190 .INDENT 0.0
 191 .TP
 192 .B MEMCACHED_BEHAVIOR_SORT_HOSTS
 193 .UNINDENT
 194 .sp
 195 Enabling this will cause hosts that are added to be placed in the host list in sorted order. This will defeat consisten hashing.
 196 .INDENT 0.0
 197 .TP
 198 .B MEMCACHED_BEHAVIOR_CONNECT_TIMEOUT
 199 .UNINDENT
 200 .sp
 201 In non\-blocking mode this changes the value of the timeout during socket connection.
 202 .INDENT 0.0
 203 .TP
 204 .B MEMCACHED_BEHAVIOR_BINARY_PROTOCOL
 205 .UNINDENT
 206 .sp
 207 Enable the use of the binary protocol. Please note that you cannot toggle this flag on an open connection.
 208 .INDENT 0.0
 209 .TP
 210 .B MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT
 211 .UNINDENT
 212 .sp
 213 Set this value to enable the server be removed after continuous MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT times connection failure.
 214 .INDENT 0.0
 215 .TP
 216 .B MEMCACHED_BEHAVIOR_IO_MSG_WATERMARK
 217 .UNINDENT
 218 .sp
 219 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).
 220 .INDENT 0.0
 221 .TP
 222 .B MEMCACHED_BEHAVIOR_IO_BYTES_WATERMARK
 223 .UNINDENT
 224 .sp
 225 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).
 226 .INDENT 0.0
 227 .TP
 228 .B MEMCACHED_BEHAVIOR_IO_KEY_PREFETCH
 229 .UNINDENT
 230 .sp
 231 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.
 232 .INDENT 0.0
 233 .TP
 234 .B MEMCACHED_BEHAVIOR_NOREPLY
 235 .UNINDENT
 236 .sp
 237 Set this value to specify that you really don\(aqt care about the result from your storage commands (set, add, replace, append, prepend).
 238 .INDENT 0.0
 239 .TP
 240 .B MEMCACHED_BEHAVIOR_NUMBER_OF_REPLICAS
 241 .UNINDENT
 242 .sp
 243 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 \(aqn\(aq next servers specified in your server list).
 244 .INDENT 0.0
 245 .TP
 246 .B MEMCACHED_BEHAVIOR_RANDOMIZE_REPLICA_READ
 247 .UNINDENT
 248 .sp
 249 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 \(aqn\(aq 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.
 250 .INDENT 0.0
 251 .TP
 252 .B MEMCACHED_BEHAVIOR_CORK
 253 .UNINDENT
 254 .sp
 255 This open has been deprecated with the behavior now built and used appropriately on selected platforms.
 256 .INDENT 0.0
 257 .TP
 258 .B MEMCACHED_BEHAVIOR_KEEPALIVE
 259 .UNINDENT
 260 .sp
 261 Enable TCP_KEEPALIVE behavior.
 262 .INDENT 0.0
 263 .TP
 264 .B MEMCACHED_BEHAVIOR_KEEPALIVE_IDLE
 265 .UNINDENT
 266 .sp
 267 Specify time, in seconds, to mark a connection as idle. This is only available as an option Linux.
 268 .INDENT 0.0
 269 .TP
 270 .B MEMCACHED_BEHAVIOR_SOCKET_SEND_SIZE
 271 .UNINDENT
 272 .sp
 273 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.
 274 .INDENT 0.0
 275 .TP
 276 .B MEMCACHED_BEHAVIOR_SOCKET_RECV_SIZE
 277 .UNINDENT
 278 .sp
 279 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.
 280 .INDENT 0.0
 281 .TP
 282 .B MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT
 283 .UNINDENT
 284 .sp
 285 Deprecated since version 0.48: See \fI\%MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS\fP
 286 .sp
 287 This number of times a host can have an error before it is disabled.
 288
 289 .INDENT 0.0
 290 .TP
 291 .B MEMCACHED_BEHAVIOR_AUTO_EJECT_HOSTS
 292 .UNINDENT
 293 .sp
 294 Deprecated since version 0.48: See \fI\%MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS\fP
 295 .sp
 296 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.
 297
 298 .INDENT 0.0
 299 .TP
 300 .B MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS
 301 .
 302 If enabled any hosts which have been flagged as disabled will be removed from the list of servers in the memcached_st structure.
 303 .UNINDENT
 304 .INDENT 0.0
 305 .TP
 306 .B MEMCACHED_BEHAVIOR_RETRY_TIMEOUT
 307 .UNINDENT
 308 .sp
 309 When enabled a host which is problematic will only be checked for usage based on the amount of time set by this behavior. The value is in seconds.
 310 .INDENT 0.0
 311 .TP
 312 .B MEMCACHED_BEHAVIOR_HASH_WITH_PREFIX_KEY
 313 .UNINDENT
 314 .sp
 315 When enabled the prefix key will be added to the key when determining server
 316 by hash. See \fBMEMCACHED_CALLBACK_NAMESPACE\fP for additional
 317 information.
 318 .SH RETURN
 319 .sp
 320 memcached_behavior_get() returns either the current value of the get, or 0
 321 or 1 on simple flag behaviors (1 being enabled). memcached_behavior_set()
 322 returns failure or success.
 323 .SH NOTES
 324 .sp
 325 memcached_behavior_set() in version .17 was changed from taking a pointer
 326 to data value, to taking a uin64_t.
 327 .SH HOME
 328 .sp
 329 To find out more information please check:
 330 \fI\%http://libmemcached.org/\fP
 331 .SH SEE ALSO
 332 .sp
 333 \fImemcached(1)\fP \fIlibmemcached(3)\fP \fImemcached_strerror(3)\fP
 334 .SH AUTHOR
 335 Brian Aker
 336 .SH COPYRIGHT
 337 2011, Brian Aker DataDifferential, http://datadifferential.com/
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