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

   1 .TH "MEMCACHED_BEHAVIOR" "3" "April 11, 2011" "0.47" "libmemcached"
   2 .SH NAME
   3 memcached_behavior \- libmemcached Documentation
   4 .
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  32 .
  33 .sp
  34 Manipulate behavior
  35 .SH LIBRARY
  36 .sp
  37 C Client Library for memcached (libmemcached, \-lmemcached)
  38 .SH SYNOPSIS
  39 .sp
  40 #include <libmemcached/memcached.h>
  41 .INDENT 0.0
  42 .TP
  43 .B uint64_t memcached_behavior_get (memcached_st *ptr, memcached_behavior flag);
  44 .UNINDENT
  45 .INDENT 0.0
  46 .TP
  47 .B memcached_return_t memcached_behavior_set (memcached_st *ptr, memcached_behavior flag, uint64_t data);
  48 .UNINDENT
  49 .SH DESCRIPTION
  50 .sp
  51 \fIlibmemcached(3)\fP behavior can be modified by use memcached_behavior_set().
  52 Default behavior is the library strives to be quick and accurate. Some
  53 behavior, while being faster, can also result in not entirely accurate
  54 behavior (for instance, memcached_set() will always respond with
  55 \fBMEMCACHED_SUCCESS\fP).
  56 .sp
  57 memcached_behavior_get() takes a behavior flag and returns whether or not
  58 that behavior is currently enabled in the client.
  59 .sp
  60 memcached_behavior_set() changes the value of a particular option of the
  61 client. It takes both a flag (listed below) and a value. For simple on or
  62 off options you just need to pass in a value of 1. Calls to
  63 memcached_behavior_set() will flush and reset all connections.
  64 .INDENT 0.0
  65 .TP
  66 .B MEMCACHED_BEHAVIOR_USE_UDP
  67 .UNINDENT
  68 .sp
  69 Causes \fIlibmemcached(3)\fP to use the UDP transport when communicating
  70 with a memcached server. Not all I/O operations are testsed
  71 when this behavior is enababled. The following operations will return
  72 \fBMEMCACHED_NOT_SUPPORTED\fP when executed with the MEMCACHED_BEHAVIOR_USE_UDP
  73 enabled: memcached_version(), memcached_stat(), memcached_get(),
  74 memcached_get_by_key(), memcached_mget(), memcached_mget_by_key(),
  75 memcached_fetch(), memcached_fetch_result(), memcached_value_fetch().
  76 .sp
  77 All other operations are testsed but are executed in a \(aqfire\-and\-forget\(aq
  78 mode, in which once the client has executed the operation, no attempt
  79 will be made to ensure the operation has been received and acted on by the
  80 server.
  81 .sp
  82 \fIlibmemcached(3)\fP does not allow TCP and UDP servers to be shared within
  83 the same libmemached(3) client \(aqinstance\(aq. An attempt to add a TCP server
  84 when this behavior is enabled will result in a \fBMEMCACHED_INVALID_HOST_PROTOCOL\fP,
  85 as will attempting to add a UDP server when this behavior has not been enabled.
  86 .INDENT 0.0
  87 .TP
  88 .B MEMCACHED_BEHAVIOR_NO_BLOCK
  89 .UNINDENT
  90 .sp
  91 Causes \fIlibmemcached(3)\fP to use asychronous IO. This is the fastest transport
  92 available for storage functions.
  93 .INDENT 0.0
  94 .TP
  95 .B MEMCACHED_BEHAVIOR_SND_TIMEOUT
  96 .UNINDENT
  97 .sp
  98 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.
  99 .INDENT 0.0
 100 .TP
 101 .B MEMCACHED_BEHAVIOR_RCV_TIMEOUT
 102 .UNINDENT
 103 .sp
 104 This sets the microsecond behavior of the socket against the SO_RCVTIMEO flag.
 105 .sp
 106 In cases where you cannot use non\-blocking IO this will allow you to still have timeouts on the reading of data.
 107 .INDENT 0.0
 108 .TP
 109 .B MEMCACHED_BEHAVIOR_TCP_NODELAY
 110 .UNINDENT
 111 .sp
 112 Turns on the no\-delay feature for connecting sockets (may be faster in some
 113 environments).
 114 .INDENT 0.0
 115 .TP
 116 .B MEMCACHED_BEHAVIOR_HASH
 117 .UNINDENT
 118 .sp
 119 Makes the default hashing algorithm for keys use MD5. 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, MEMCACHED_HASH_FNV1A_32, MEMCACHED_HASH_JENKINS, MEMCACHED_HASH_HSIEH, and MEMCACHED_HASH_MURMUR.
 120 .sp
 121 Each hash has it\(aqs advantages and it\(aqs weaknesses. If you don\(aqt know or don\(aqt care, just go with the default.
 122 .sp
 123 Support for 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.
 124 .INDENT 0.0
 125 .TP
 126 .B MEMCACHED_BEHAVIOR_DISTRIBUTION
 127 .UNINDENT
 128 .sp
 129 Using this you can enable different means of distributing values to servers.
 130 .sp
 131 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.
 132 .INDENT 0.0
 133 .TP
 134 .B MEMCACHED_BEHAVIOR_CACHE_LOOKUPS
 135 .UNINDENT
 136 .sp
 137 DEPRECATED. Memcached can cache named lookups so that DNS lookups are made only once.
 138 .INDENT 0.0
 139 .TP
 140 .B MEMCACHED_BEHAVIOR_SUPPORT_CAS
 141 .UNINDENT
 142 .sp
 143 Support CAS operations (this is not enabled by default at this point in the server since it imposes a slight performance penalty).
 144 .INDENT 0.0
 145 .TP
 146 .B MEMCACHED_BEHAVIOR_KETAMA
 147 .UNINDENT
 148 .sp
 149 Sets the default distribution to MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA and the hash to MEMCACHED_HASH_MD5.
 150 .INDENT 0.0
 151 .TP
 152 .B MEMCACHED_BEHAVIOR_KETAMA_WEIGHTED
 153 .UNINDENT
 154 .sp
 155 Sets the default distribution to MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA with the weighted tests.  and the hash to MEMCACHED_HASH_MD5.
 156 .INDENT 0.0
 157 .TP
 158 .B MEMCACHED_BEHAVIOR_KETAMA_HASH
 159 .UNINDENT
 160 .sp
 161 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.
 162 .INDENT 0.0
 163 .TP
 164 .B MEMCACHED_BEHAVIOR_KETAMA_COMPAT
 165 .UNINDENT
 166 .sp
 167 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.
 168 .INDENT 0.0
 169 .TP
 170 .B MEMCACHED_BEHAVIOR_POLL_TIMEOUT
 171 .UNINDENT
 172 .sp
 173 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.
 174 .INDENT 0.0
 175 .TP
 176 .B MEMCACHED_BEHAVIOR_USER_DATA
 177 .UNINDENT
 178 .sp
 179 DEPRECATED
 180 .INDENT 0.0
 181 .TP
 182 .B MEMCACHED_BEHAVIOR_BUFFER_REQUESTS
 183 .UNINDENT
 184 .sp
 185 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.
 186 .INDENT 0.0
 187 .TP
 188 .B MEMCACHED_BEHAVIOR_VERIFY_KEY
 189 .UNINDENT
 190 .sp
 191 Enabling this will cause \fIlibmemcached(3)\fP to test all keys to verify that they are valid keys.
 192 .INDENT 0.0
 193 .TP
 194 .B MEMCACHED_BEHAVIOR_SORT_HOSTS
 195 .UNINDENT
 196 .sp
 197 Enabling this will cause hosts that are added to be placed in the host list in sorted order. This will defeat consisten hashing.
 198 .INDENT 0.0
 199 .TP
 200 .B MEMCACHED_BEHAVIOR_CONNECT_TIMEOUT
 201 .UNINDENT
 202 .sp
 203 In non\-blocking mode this changes the value of the timeout during socket connection.
 204 .INDENT 0.0
 205 .TP
 206 .B MEMCACHED_BEHAVIOR_BINARY_PROTOCOL
 207 .UNINDENT
 208 .sp
 209 Enable the use of the binary protocol. Please note that you cannot toggle this flag on an open connection.
 210 .INDENT 0.0
 211 .TP
 212 .B MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT
 213 .UNINDENT
 214 .sp
 215 Set this value to enable the server be removed after continuous MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT times connection failure.
 216 .INDENT 0.0
 217 .TP
 218 .B MEMCACHED_BEHAVIOR_IO_MSG_WATERMARK
 219 .UNINDENT
 220 .sp
 221 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).
 222 .INDENT 0.0
 223 .TP
 224 .B MEMCACHED_BEHAVIOR_IO_BYTES_WATERMARK
 225 .UNINDENT
 226 .sp
 227 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).
 228 .INDENT 0.0
 229 .TP
 230 .B MEMCACHED_BEHAVIOR_IO_KEY_PREFETCH
 231 .UNINDENT
 232 .sp
 233 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.
 234 .INDENT 0.0
 235 .TP
 236 .B MEMCACHED_BEHAVIOR_NOREPLY
 237 .UNINDENT
 238 .sp
 239 Set this value to specify that you really don\(aqt care about the result from your storage commands (set, add, replace, append, prepend).
 240 .INDENT 0.0
 241 .TP
 242 .B MEMCACHED_BEHAVIOR_NUMBER_OF_REPLICAS
 243 .UNINDENT
 244 .sp
 245 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).
 246 .INDENT 0.0
 247 .TP
 248 .B MEMCACHED_BEHAVIOR_RANDOMIZE_REPLICA_READ
 249 .UNINDENT
 250 .sp
 251 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.
 252 .INDENT 0.0
 253 .TP
 254 .B MEMCACHED_BEHAVIOR_CORK
 255 .UNINDENT
 256 .sp
 257 This open has been deprecated with the behavior now built and used appropriately on selected platforms.
 258 .INDENT 0.0
 259 .TP
 260 .B MEMCACHED_BEHAVIOR_KEEPALIVE
 261 .UNINDENT
 262 .sp
 263 Enable TCP_KEEPALIVE behavior.
 264 .INDENT 0.0
 265 .TP
 266 .B MEMCACHED_BEHAVIOR_KEEPALIVE_IDLE
 267 .UNINDENT
 268 .sp
 269 Specify time, in seconds, to mark a connection as idle. This is only available as an option Linux.
 270 .INDENT 0.0
 271 .TP
 272 .B MEMCACHED_BEHAVIOR_SOCKET_SEND_SIZE
 273 .UNINDENT
 274 .sp
 275 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.
 276 .INDENT 0.0
 277 .TP
 278 .B MEMCACHED_BEHAVIOR_SOCKET_RECV_SIZE
 279 .UNINDENT
 280 .sp
 281 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.
 282 .INDENT 0.0
 283 .TP
 284 .B MEMCACHED_BEHAVIOR_SERVER_FAILURE_LIMIT
 285 .UNINDENT
 286 .sp
 287 DEPRECATED, please see MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS. This number of times a host can have an error before it is disabled.
 288 .INDENT 0.0
 289 .TP
 290 .B MEMCACHED_BEHAVIOR_AUTO_EJECT_HOSTS
 291 .UNINDENT
 292 .sp
 293 DEPRECATED, please see MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS. 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.
 294 .INDENT 0.0
 295 .TP
 296 .B MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS
 297 .UNINDENT
 298 .sp
 299 If enabled any hosts which have been flagged as disabled will be removed from the list of servers in the memcached_st structure.
 300 .INDENT 0.0
 301 .TP
 302 .B MEMCACHED_BEHAVIOR_RETRY_TIMEOUT
 303 .UNINDENT
 304 .sp
 305 When enabled a host which is problematic will only be checked for usage based on the amount of time set by this behavior.
 306 .INDENT 0.0
 307 .TP
 308 .B MEMCACHED_BEHAVIOR_HASH_WITH_PREFIX_KEY
 309 .UNINDENT
 310 .sp
 311 When enabled the prefix key will be added to the key when determining server by hash.
 312 .SH RETURN
 313 .sp
 314 memcached_behavior_get() returns either the current value of the get, or 0
 315 or 1 on simple flag behaviors (1 being enabled). memcached_behavior_set()
 316 returns failure or success.
 317 .SH NOTES
 318 .sp
 319 memcached_behavior_set() in version .17 was changed from taking a pointer
 320 to data value, to taking a uin64_t.
 321 .SH HOME
 322 .sp
 323 To find out more information please check:
 324 \fI\%https://launchpad.net/libmemcached\fP
 325 .SH SEE ALSO
 326 .sp
 327 \fImemcached(1)\fP \fIlibmemcached(3)\fP \fImemcached_strerror(3)\fP
 328 .SH AUTHOR
 329 Brian Aker
 330 .SH COPYRIGHT
 331 2011, Brian Aker DataDifferential, http://datadifferential.com/
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