f2091de9c0309936b43c3af8437be656f4b806a7
1 RRDCACHED(1) rrdtool RRDCACHED(1)
6 rrdcached - Data caching daemon for rrdtool
9 r\brr\brd\bdc\bca\bac\bch\bhe\bed\bd [-\b-P\bP _\bp_\be_\br_\bm_\bi_\bs_\bs_\bi_\bo_\bn_\bs] [-\b-l\bl _\ba_\bd_\bd_\br_\be_\bs_\bs] [-\b-s\bs _\bg_\br_\bo_\bu_\bp] [-\b-w\bw _\bt_\bi_\bm_\be_\bo_\bu_\bt]
10 [-\b-z\bz _\bd_\be_\bl_\ba_\by] [-\b-f\bf _\bt_\bi_\bm_\be_\bo_\bu_\bt] [-\b-p\bp _\bp_\bi_\bd_\b__\bf_\bi_\bl_\be] [-\b-t\bt _\bw_\br_\bi_\bt_\be_\b__\bt_\bh_\br_\be_\ba_\bd_\bs]
11 [-\b-j\bj _\bj_\bo_\bu_\br_\bn_\ba_\bl_\b__\bd_\bi_\br] [-F] [-g] [-\b-b\bb _\bb_\ba_\bs_\be_\b__\bd_\bi_\br [-\b-B\bB]]
15 accumulates them and, if enough have been received or a defined time
17 used to force writing of values to disk, so that graphing facilities
18 and similar can work with up-to-date data.
20 The daemon was written with big setups in mind. Those setups usually
21 run into IO related problems sooner or later for reasons that are
22 beyond the scope of this document. Check the wiki at the RRDtool
23 homepage for details. Also check "SECURITY CONSIDERATIONS" below before
24 using this daemon! A detailed description of how the daemon operates
25 can be found in the "HOW IT WORKS" section below.
31 following that prefix is interpreted as the path to a UNIX domain
32 socket. Otherwise the address or node name are resolved using
33 "getaddrinfo()".
35 For network sockets, a port may be specified by using the form
36 "[\b[_\ba_\bd_\bd_\br_\be_\bs_\bs]\b]:\b:_\bp_\bo_\br_\bt_\b". If the address is an IPv4 address or a fully
37 qualified domain name (i. e. the address contains at least one dot
38 (".")), the square brackets can be omitted, resulting in the
39 (simpler) "_\ba_\bd_\bd_\br_\be_\bs_\bs:\b:_\bp_\bo_\br_\bt_\b" pattern. The default port is 4\b42\b22\b21\b17\b7/\b/u\bud\bdp\bp. If
40 you specify a network socket, it is mandatory to read the "SECURITY
41 CONSIDERATIONS" section.
43 The following formats are accepted. Please note that the address of
46 unix:</path/to/unix.sock>
47 /<path/to/unix.sock>
48 <hostname-or-ip>
49 [<hostname-or-ip>]:<port>
50 <hostname-or-ipv4>:<port>
53 "unix:/tmp/rrdcached.sock", will be used.
56 Set the group permissions of a UNIX domain socket. The option
57 accepts either a numeric group id or group name. That group will
58 then have both read and write permissions (the socket will have
59 file permissions 0750) for the socket and, therefore, is able to
60 send commands to the daemon. This may be useful in cases where you
61 cannot easily run all RRD processes with the same user privileges
62 (e.g. graph generating CGI scripts that typically run in the
63 permission context of the web server).
67 different sockets.
69 The default is not to change ownership or permissions of the socket
70 and, thus, use the system default.
73 Set the file permissions of a UNIX domain socket. The option
74 accepts an octal number representing the bit pattern for the mode
77 Please note that not all systems honor this setting. On Linux,
78 read/write permissions are required to connect to a UNIX socket.
79 However, many BSD-derived systems ignore permissions for UNIX
84 different sockets.
86 The default is not to change ownership or permissions of the socket
87 and, thus, use the system default.
90 Specifies the commands accepted via a network socket. This allows
92 various sources.
95 commands. For example, to allow the "FLUSH" and "PENDING" commands
96 one could specify:
98 rrdcached -P FLUSH,PENDING $MORE_ARGUMENTS
100 The -\b-P\bP option affects the _\bf_\bo_\bl_\bl_\bo_\bw_\bi_\bn_\bg socket addresses (the following
102 (address 10.0.0.1) will be restricted to the "FLUSH" and "PENDING"
103 commands:
105 rrdcached -l unix:/some/path -P FLUSH,PENDING -l 10.0.0.1
107 A complete list of available commands can be found in the section
108 "Valid Commands" below. There are two minor special exceptions:
110 · The "HELP" and "QUIT" commands are always allowed.
112 · If the "BATCH" command is accepted, the .\b. command will
113 automatically be accepted, too.
115 Please also read "SECURITY CONSIDERATIONS" below.
119 not specified the default interval of 300 seconds will be used.
122 If specified, rrdcached will delay writing of each RRD for a random
124 writes being queued simultaneously. This value should be no
126 delay.
130 which are written to disk. This only concerns files to which
131 updates have stopped, so setting this to a high value, such as
132 3600 seconds, is acceptable in most cases. This timeout defaults to
133 3600 seconds.
136 Sets the name and location of the PID-file. If not specified, the
137 default, "_\b$_\bl_\bo_\bc_\ba_\bl_\bs_\bt_\bs_\bt_\be_\bd_\bi_\br_\b/_\br_\bu_\bn_\b/_\br_\br_\bd_\bc_\ba_\bc_\bh_\be_\bd_\b._\bp_\bi_\bd_\b" will be used.
140 Specifies the number of threads used for writing RRD files. The
141 default is 4. Increasing this number will allow rrdcached to have
142 more simultaneous I/O requests into the kernel. This may allow the
143 kernel to re-order disk writes, resulting in better disk
144 throughput.
148 system crash, this will allow the daemon to write any updates that
149 were pending at the time of the crash.
151 On startup, the daemon will check for journal files in this
152 directory. If found, all updates therein will be read into memory
153 before the daemon starts accepting new connections.
155 The journal will be rotated with the same frequency as the flush
158 When journaling is enabled, the daemon will use a fast shutdown
159 procedure. Rather than flushing all files to disk, it will make
160 sure the journal is properly written and exit immediately.
161 Although the RRD data files are not fully up-to-date, no
162 information is lost; all pending updates will be replayed from the
163 journal next time the daemon starts up.
168 shut down, regardless of journal setting.
173 The daemon will change into a specific directory at startup. All
175 will be interpreted to be relative to this directory. If not given
176 the default, "/tmp", will be used.
178 +------------------------+------------------------+
179 ! Command line ! File updated !
180 +------------------------+------------------------+
181 ! foo.rrd ! /tmp/foo.rrd !
182 ! foo/bar.rrd ! /tmp/foo/bar.rrd !
183 ! /var/lib/rrd/foo.rrd ! /var/lib/rrd/foo.rrd !
184 +------------------------+------------------------+
185 Paths given on the command line and paths actually
186 updated by the daemon, assuming the base directory
187 "/tmp".
189 W\bWA\bAR\bRN\bNI\bIN\bNG\bG:\b: The paths up to and including the base directory M\bMU\bUS\bST\bT N\bNO\bOT\bT
191 specified as:
193 -b /base/dir/somewhere
197 /base
198 /base/dir
199 /base/dir/somewhere
203 containing "../" will also be blocked.
210 · dump
212 · fetch
214 · flush
216 · graph
218 · graphv
220 · info
222 · last
224 · lastupdate
226 · update
228 · xport
232 (see below) to the daemon before accessing the files, so they work with
233 up-to-date data even if the cache timeout is large.
236 The daemon reports errors in one of two ways: During startup, error
237 messages are printed to "STDERR". One of the steps when starting up is
238 to fork to the background and closing "STDERR" - after this writing
239 directly to the user is no longer possible. Once this has happened, the
240 daemon will send log messages to the system logging daemon using
245 for an entry for that file in its internal tree. If not found, an entry
246 is created including the current time (called "First" in the diagram
248 time the operating system considers to be "now". The value and time of
249 the value (called "Time" in the diagram below) are appended to the tree
250 node.
252 When appending a value to a tree node, it is checked whether it's time
253 to write the values to disk. Values are written to disk if
254 "now() - First >= timeout", where "timeout" is the timeout specified
256 will be enqueued in the "update queue", i. e. they will be appended to
257 the linked list shown below. Because the tree nodes and the elements
258 of the linked list are the same data structures in memory, any update
259 to a file that has already been enqueued will be written with the next
260 write to the RRD file, too.
262 A separate "update thread" constantly dequeues the first element in the
263 update queue and writes all its values to the appropriate file. So as
264 long as the update queue is not empty files are written at the highest
265 possible rate.
267 Since the timeout of files is checked only when new values are added to
268 the file, "dead" files, i. e. files that are not updated anymore, would
269 never be written to disk. Therefore, every now and then, controlled by
271 enqueued. Since this only affects "dead" files and walking the tree is
272 relatively expensive, you should set the "flush interval" to a
273 reasonably high value. The default is 3600 seconds (one hour).
275 The downside of caching values is that they won't show up in graphs
276 generated from the RRD files. To get around this, the daemon provides
277 the "flush command" to flush specific files. This means that the file
279 already enqueued. The flush command will return only after the file's
280 pending updates have been written to disk.
282 +------+ +------+ +------+
283 ! head ! ! root ! ! tail !
284 +---+--+ +---+--+ +---+--+
285 ! /\ !
286 ! / \ !
287 ! /\ /\ !
288 ! /\/\ \ `----------------- ... --------, !
289 V / `-------, ! V
290 +---+----+---+ +------+-----+ +---+----+---+
291 ! File: foo ! ! File: bar ! ! File: qux !
292 ! First: 101 ! ! First: 119 ! ! First: 180 !
293 ! Next:&bar -+--->! Next:&... -+---> ... --->! Next:NULL !
294 | Prev:NULL !<---+-Prev:&foo !<--- ... ----+-Prev: &... !
295 +============+ +============+ +============+
296 ! Time: 100 ! ! Time: 120 ! ! Time: 180 !
297 ! Value: 10 ! ! Value: 0.1 ! ! Value: 2,2 !
298 +------------+ +------------+ +------------+
299 ! Time: 110 ! ! Time: 130 ! ! Time: 190 !
300 ! Value: 26 ! ! Value: 0.1 ! ! Value: 7,3 !
301 +------------+ +------------+ +------------+
302 : : : : : :
303 +------------+ +------------+ +------------+
304 ! Time: 230 ! ! Time: 250 ! ! Time: 310 !
305 ! Value: 42 ! ! Value: 0.2 ! ! Value: 1,2 !
306 +------------+ +------------+ +------------+
308 The above diagram demonstrates:
310 · Files/values are stored in a (balanced) tree.
312 · Tree nodes and entries in the update queue are the same data
313 structure.
315 · The local time ("First") and the time specified in updates ("Time")
316 may differ.
318 · Timed out values are inserted at the "tail".
320 · Explicitly flushed values are inserted at the "head".
322 · ASCII art rocks.
326 There is no authentication.
328 The client/server protocol does not yet have any authentication
329 mechanism. It is likely that authentication and encryption will be
330 added in a future version, but for the time being it is the
331 administrator's responsibility to secure the traffic from/to the
332 daemon!
334 It is highly recommended to install a packet filter or similar
335 mechanism to prevent unauthorized connections. Unless you have a
336 dedicated VLAN or VPN for this, using network sockets is probably a bad
337 idea!
340 There is minimal per-socket authorization.
342 Authorization is currently done on a per-socket basis. That means each
343 socket has a list of commands it will accept and it will accept. It
344 will accept only those commands explicitly listed but it will
345 (currently) accept these commands from anyone reaching the socket.
347 If the networking sockets are to be used, it is necessary to restrict
348 the accepted commands to those needed by external clients. If, for
349 example, external clients want to draw graphs of the cached data, they
350 should only be allowed to use the "FLUSH" command.
353 There is no encryption.
355 Again, this may be added in the future, but for the time being it is
356 your job to keep your private data private. Install a VPN or an
357 encrypted tunnel if you statistics are confidential!
360 There is no sanity checking.
362 The daemon will blindly write to any file it gets told, so you really
363 should create a separate user just for this daemon. Also it does not do
364 any sanity checks, so if it gets told to write values for a time far in
365 the future, your files will be messed up good!
368 · Security is the job of the administrator.
370 · We recommend to allow write access via UNIX domain sockets only.
372 · You have been warned.
375 The daemon communicates with clients using a line based ASCII protocol
376 which is easy to read and easy to type. This makes it easy for scripts
377 to implement the protocol and possible for users to use telnet to
378 connect to the daemon and test stuff "by hand".
380 The protocol is line based, this means that each record consists of one
381 or more lines. A line is terminated by the line feed character 0x0A,
382 commonly written as "\n". In the examples below, this character will be
383 written as "<LF>" ("line feed").
385 After the connection has been established, the client is expected to
386 send a "command". A command consists of the command keyword, possibly
387 some arguments, and a terminating newline character. For a list of
388 commands, see "Valid Commands" below.
390 Example:
392 FLUSH /tmp/foo.rrd<LF>
394 The daemon answers with a line consisting of a status code and a short
395 status message, separated by one or more space characters. A negative
396 status code signals an error, a positive status code or zero signal
397 success. If the status code is greater than zero, it indicates the
398 number of lines that follow the status line.
400 Examples:
402 0 Success<LF>
404 2 Two lines follow<LF>
405 This is the first line<LF>
406 And this is the second line<LF>
409 The following commands are understood by the daemon:
412 Causes the daemon to put _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be to the h\bhe\bea\bad\bd of the update queue
413 (possibly moving it there if the node is already enqueued). The
417 Causes the daemon to start flushing ALL pending values to disk.
418 This returns immediately, even though the writes may take a long
419 time.
422 Shows any "pending" updates for a file, in order. The updates
423 shown have not yet been written to the underlying RRD file.
426 Removes _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be from the cache. Any pending updates W\bWI\bIL\bLL\bL B\bBE\bE L\bLO\bOS\bST\bT.
429 Shows the files that are on the output queue. Returns zero or more
430 lines in the following format, where <num_vals> is the number of
431 values to be written for the <file>:
433 <num_vals> <file>
438 Otherwise a short description, possibly containing a pointer to a
439 manual page, is returned. Obviously, this is meant for interactive
440 usage and the format in which the commands and usage summaries are
441 returned is not well defined.
444 Returns a list of metrics which can be used to measure the daemons
445 performance and check its status. For a description of the values
446 returned, see "Performance Values" below.
448 The format in which the values are returned is similar to many
449 other line based protocols: Each value is printed on a separate
450 line, each consisting of the name of the value, a colon, one or
451 more spaces and the actual value.
453 Example:
455 9 Statistics follow
456 QueueLength: 0
457 UpdatesReceived: 30
458 FlushesReceived: 2
459 UpdatesWritten: 13
460 DataSetsWritten: 390
461 TreeNodesNumber: 13
462 TreeDepth: 4
463 JournalBytes: 190
464 JournalRotate: 0
466 U\bUP\bPD\bDA\bAT\bTE\bE _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be _\bv_\ba_\bl_\bu_\be_\bs [_\bv_\ba_\bl_\bu_\be_\bs ...]
468 designed for, so describing the mechanism again is unnecessary.
469 Read "HOW IT WORKS" above for a detailed explanation.
471 Note that rrdcached only accepts absolute timestamps in the update
472 values. Updates strings like "N:1:2:3" are automatically converted
473 to absolute time by the RRD client library before sending to
474 rrdcached.
477 This command is written to the journal after a file is successfully
478 written out to disk. It is used during journal replay to determine
480 journal; it is not accepted from the other command channels.
483 This command initiates the bulk load of multiple commands. This is
484 designed for installations with extremely high update rates, since
488 All commands are executed just as they would be if given
489 individually, except for output to the user. Messages indicating
490 success are suppressed, and error messages are delayed until the
491 client is finished.
493 Command processing is finished when the client sends a dot (".") on
494 its own line. After the client has finished, the server responds
495 with an error count and the list of error messages (if any). Each
496 error messages indicates the number of the command to which it
497 corresponds, and the error message itself. The first user command
500 client: BATCH
501 server: 0 Go ahead. End with dot '.' on its own line.
502 client: UPDATE x.rrd 1223661439:1:2:3 <--- command #1
503 client: UPDATE y.rrd 1223661440:3:4:5 <--- command #2
504 client: and so on...
505 client: .
506 server: 2 Errors
507 server: 1 message for command 1
508 server: 12 message for command 12
511 Disconnect from rrdcached.
516 Q\bQu\bue\beu\bue\beL\bLe\ben\bng\bgt\bth\bh _\b(_\bu_\bn_\bs_\bi_\bg_\bn_\be_\bd _\b6_\b4_\bb_\bi_\bt _\bi_\bn_\bt_\be_\bg_\be_\br_\b)
517 Number of nodes currently enqueued in the update queue.
519 U\bUp\bpd\bda\bat\bte\bes\bsR\bRe\bec\bce\bei\biv\bve\bed\bd _\b(_\bu_\bn_\bs_\bi_\bg_\bn_\be_\bd _\b6_\b4_\bb_\bi_\bt _\bi_\bn_\bt_\be_\bg_\be_\br_\b)
520 Number of UPDATE commands received.
522 F\bFl\blu\bus\bsh\bhe\bes\bsR\bRe\bec\bce\bei\biv\bve\bed\bd _\b(_\bu_\bn_\bs_\bi_\bg_\bn_\be_\bd _\b6_\b4_\bb_\bi_\bt _\bi_\bn_\bt_\be_\bg_\be_\br_\b)
523 Number of FLUSH commands received.
525 U\bUp\bpd\bda\bat\bte\bes\bsW\bWr\bri\bit\btt\bte\ben\bn _\b(_\bu_\bn_\bs_\bi_\bg_\bn_\be_\bd _\b6_\b4_\bb_\bi_\bt _\bi_\bn_\bt_\be_\bg_\be_\br_\b)
526 Total number of updates, i. e. calls to "rrd_update_r", since the
527 daemon was started.
529 D\bDa\bat\bta\baS\bSe\bet\bts\bsW\bWr\bri\bit\btt\bte\ben\bn _\b(_\bu_\bn_\bs_\bi_\bg_\bn_\be_\bd _\b6_\b4_\bb_\bi_\bt _\bi_\bn_\bt_\be_\bg_\be_\br_\b)
530 Total number of "data sets" written to disk since the daemon was
532 command. For example: "1223661439:123:456" is one data set with two
533 values. The term "data set" is used to prevent confusion whether
534 individual values or groups of values are counted.
536 T\bTr\bre\bee\beN\bNo\bod\bde\bes\bsN\bNu\bum\bmb\bbe\ber\br _\b(_\bu_\bn_\bs_\bi_\bg_\bn_\be_\bd _\b6_\b4_\bb_\bi_\bt _\bi_\bn_\bt_\be_\bg_\be_\br_\b)
537 Number of nodes in the cache.
539 T\bTr\bre\bee\beD\bDe\bep\bpt\bth\bh _\b(_\bu_\bn_\bs_\bi_\bg_\bn_\be_\bd _\b6_\b4_\bb_\bi_\bt _\bi_\bn_\bt_\be_\bg_\be_\br_\b)
540 Depth of the tree used for fast key lookup.
542 J\bJo\bou\bur\brn\bna\bal\blB\bBy\byt\bte\bes\bs _\b(_\bu_\bn_\bs_\bi_\bg_\bn_\be_\bd _\b6_\b4_\bb_\bi_\bt _\bi_\bn_\bt_\be_\bg_\be_\br_\b)
543 Total number of bytes written to the journal since startup.
545 J\bJo\bou\bur\brn\bna\bal\blR\bRo\bot\bta\bat\bte\be _\b(_\bu_\bn_\bs_\bi_\bg_\bn_\be_\bd _\b6_\b4_\bb_\bi_\bt _\bi_\bn_\bt_\be_\bg_\be_\br_\b)
546 Number of times the journal has been rotated since startup.
549 SIGINT and SIGTERM
550 The daemon exits normally on receipt of either of these signals.
552 options.
554 SIGUSR1
555 The daemon exits AFTER flushing all updates out to disk. This may
556 take a while.
558 SIGUSR2
559 The daemon exits immediately, without flushing updates out to disk.
560 Pending updates will be replayed from the journal when the daemon
561 starts up again. W\bWA\bAR\bRN\bNI\bIN\bNG\bG:\b: i\bif\bf j\bjo\bou\bur\brn\bna\bal\bli\bin\bng\bg (\b(-\b-j\bj)\b) i\bis\bs N\bNO\bOT\bT e\ben\bna\bab\bbl\ble\bed\bd,\b, a\ban\bny\by
562 p\bpe\ben\bnd\bdi\bin\bng\bg u\bup\bpd\bda\bat\bte\bes\bs W\bWI\bIL\bLL\bL B\bBE\bE L\bLO\bOS\bST\bT.
565 No known bugs at the moment.
568 rrdtool, rrdgraph
571 Florian Forster <octo at verplant.org>
576 kevin brintnall <kbrint@rufus.net>
580 1.4.3 2010-03-22 RRDCACHED(1)