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/t\btc\bcp\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 been specified), i.e., you may specify different settings for
68 different sockets.
70 The default is not to change ownership or permissions of the socket
71 and, thus, use the system default.
74 Set the file permissions of a UNIX domain socket. The option
75 accepts an octal number representing the bit pattern for the mode
78 Please note that not all systems honor this setting. On Linux,
79 read/write permissions are required to connect to a UNIX socket.
80 However, many BSD-derived systems ignore permissions for UNIX
85 been specified), i.e., you may specify different settings for
86 different sockets.
88 The default is not to change ownership or permissions of the socket
89 and, thus, use the system default.
92 Specifies the commands accepted via a network socket. This allows
94 various sources.
97 commands. For example, to allow the "FLUSH" and "PENDING" commands
98 one could specify:
100 rrdcached -P FLUSH,PENDING $MORE_ARGUMENTS
102 The -\b-P\bP option affects the _\bf_\bo_\bl_\bl_\bo_\bw_\bi_\bn_\bg socket addresses (the following
104 specified). In the following example, only the IPv4 network socket
105 (address 10.0.0.1) will be restricted to the "FLUSH" and "PENDING"
106 commands:
108 rrdcached -l unix:/some/path -P FLUSH,PENDING -l 10.0.0.1
110 A complete list of available commands can be found in the section
111 "Valid Commands" below. There are two minor special exceptions:
113 · The "HELP" and "QUIT" commands are always allowed.
115 · If the "BATCH" command is accepted, the .\b. command will
116 automatically be accepted, too.
118 Please also read "SECURITY CONSIDERATIONS" below.
122 not specified the default interval of 300 seconds will be used.
125 If specified, rrdcached will delay writing of each RRD for a random
127 writes being queued simultaneously. This value should be no
129 delay.
133 which are written to disk. This only concerns files to which
134 updates have stopped, so setting this to a high value, such as
135 3600 seconds, is acceptable in most cases. This timeout defaults to
136 3600 seconds.
139 Sets the name and location of the PID-file. If not specified, the
140 default, "_\b$_\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.
143 Specifies the number of threads used for writing RRD files. The
144 default is 4. Increasing this number will allow rrdcached to have
145 more simultaneous I/O requests into the kernel. This may allow the
146 kernel to re-order disk writes, resulting in better disk
147 throughput.
151 system crash, this will allow the daemon to write any updates that
152 were pending at the time of the crash.
154 On startup, the daemon will check for journal files in this
155 directory. If found, all updates therein will be read into memory
156 before the daemon starts accepting new connections.
158 The journal will be rotated with the same frequency as the flush
161 When journaling is enabled, the daemon will use a fast shutdown
162 procedure. Rather than flushing all files to disk, it will make
163 sure the journal is properly written and exit immediately.
164 Although the RRD data files are not fully up-to-date, no
165 information is lost; all pending updates will be replayed from the
166 journal next time the daemon starts up.
171 shut down, regardless of journal setting.
176 The daemon will change into a specific directory at startup. All
178 will be interpreted to be relative to this directory. If not given
179 the default, "/tmp", will be used.
181 +------------------------+------------------------+
182 ! Command line ! File updated !
183 +------------------------+------------------------+
184 ! foo.rrd ! /tmp/foo.rrd !
185 ! foo/bar.rrd ! /tmp/foo/bar.rrd !
186 ! /var/lib/rrd/foo.rrd ! /var/lib/rrd/foo.rrd !
187 +------------------------+------------------------+
188 Paths given on the command line and paths actually
189 updated by the daemon, assuming the base directory
190 "/tmp".
192 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
194 specified as:
196 -b /base/dir/somewhere
200 /base
201 /base/dir
202 /base/dir/somewhere
206 containing "../" will also be blocked.
213 · dump
215 · fetch
217 · flush
219 · graph
221 · graphv
223 · info
225 · last
227 · lastupdate
229 · update
231 · xport
235 (see below) to the daemon before accessing the files, so they work with
236 up-to-date data even if the cache timeout is large.
239 The daemon reports errors in one of two ways: During startup, error
240 messages are printed to "STDERR". One of the steps when starting up is
241 to fork to the background and closing "STDERR" - after this writing
242 directly to the user is no longer possible. Once this has happened, the
243 daemon will send log messages to the system logging daemon using
248 for an entry for that file in its internal tree. If not found, an entry
249 is created including the current time (called "First" in the diagram
251 time the operating system considers to be "now". The value and time of
252 the value (called "Time" in the diagram below) are appended to the tree
253 node.
255 When appending a value to a tree node, it is checked whether it's time
256 to write the values to disk. Values are written to disk if
257 "now() - First >= timeout", where "timeout" is the timeout specified
259 will be enqueued in the "update queue", i. e. they will be appended to
260 the linked list shown below. Because the tree nodes and the elements
261 of the linked list are the same data structures in memory, any update
262 to a file that has already been enqueued will be written with the next
263 write to the RRD file, too.
265 A separate "update thread" constantly dequeues the first element in the
266 update queue and writes all its values to the appropriate file. So as
267 long as the update queue is not empty files are written at the highest
268 possible rate.
270 Since the timeout of files is checked only when new values are added to
271 the file, "dead" files, i. e. files that are not updated anymore, would
272 never be written to disk. Therefore, every now and then, controlled by
274 enqueued. Since this only affects "dead" files and walking the tree is
275 relatively expensive, you should set the "flush interval" to a
276 reasonably high value. The default is 3600 seconds (one hour).
278 The downside of caching values is that they won't show up in graphs
279 generated from the RRD files. To get around this, the daemon provides
280 the "flush command" to flush specific files. This means that the file
282 already enqueued. The flush command will return only after the file's
283 pending updates have been written to disk.
285 +------+ +------+ +------+
286 ! head ! ! root ! ! tail !
287 +---+--+ +---+--+ +---+--+
288 ! /\ !
289 ! / \ !
290 ! /\ /\ !
291 ! /\/\ \ `----------------- ... --------, !
292 V / `-------, ! V
293 +---+----+---+ +------+-----+ +---+----+---+
294 ! File: foo ! ! File: bar ! ! File: qux !
295 ! First: 101 ! ! First: 119 ! ! First: 180 !
296 ! Next:&bar -+--->! Next:&... -+---> ... --->! Next:NULL !
297 | Prev:NULL !<---+-Prev:&foo !<--- ... ----+-Prev: &... !
298 +============+ +============+ +============+
299 ! Time: 100 ! ! Time: 120 ! ! Time: 180 !
300 ! Value: 10 ! ! Value: 0.1 ! ! Value: 2,2 !
301 +------------+ +------------+ +------------+
302 ! Time: 110 ! ! Time: 130 ! ! Time: 190 !
303 ! Value: 26 ! ! Value: 0.1 ! ! Value: 7,3 !
304 +------------+ +------------+ +------------+
305 : : : : : :
306 +------------+ +------------+ +------------+
307 ! Time: 230 ! ! Time: 250 ! ! Time: 310 !
308 ! Value: 42 ! ! Value: 0.2 ! ! Value: 1,2 !
309 +------------+ +------------+ +------------+
311 The above diagram demonstrates:
313 · Files/values are stored in a (balanced) tree.
315 · Tree nodes and entries in the update queue are the same data
316 structure.
318 · The local time ("First") and the time specified in updates ("Time")
319 may differ.
321 · Timed out values are inserted at the "tail".
323 · Explicitly flushed values are inserted at the "head".
325 · ASCII art rocks.
329 If your rrdtool installation was built without libwrap there is no form
330 of authentication for clients connecting to the rrdcache daemon!
332 If your rrdtool installation was built with libwrap then you can use
333 hosts_access to restrict client access to the rrdcache daemon
334 (rrdcached). For more information on how to use hosts_access to
335 restrict access to the rrdcache daemon you should read the
338 It is still highly recommended to install a packet filter or similar
339 mechanism to prevent unauthorized connections. Unless you have a
340 dedicated VLAN or VPN for this, using network sockets is probably a bad
341 idea!
344 There is minimal per-socket authorization.
346 Authorization is currently done on a per-socket basis. That means each
347 socket has a list of commands it will accept and it will accept. It
348 will accept only those commands explicitly listed but it will
349 (currently) accept these commands from anyone reaching the socket.
351 If the networking sockets are to be used, it is necessary to restrict
352 the accepted commands to those needed by external clients. If, for
353 example, external clients want to draw graphs of the cached data, they
354 should only be allowed to use the "FLUSH" command.
357 There is no encryption.
359 Again, this may be added in the future, but for the time being it is
360 your job to keep your private data private. Install a VPN or an
361 encrypted tunnel if you statistics are confidential!
364 There is no sanity checking.
366 The daemon will blindly write to any file it gets told, so you really
367 should create a separate user just for this daemon. Also it does not do
368 any sanity checks, so if it gets told to write values for a time far in
369 the future, your files will be messed up good!
372 · Security is the job of the administrator.
374 · We recommend to allow write access via UNIX domain sockets only.
376 · You have been warned.
379 The daemon communicates with clients using a line based ASCII protocol
380 which is easy to read and easy to type. This makes it easy for scripts
381 to implement the protocol and possible for users to use telnet to
382 connect to the daemon and test stuff "by hand".
384 The protocol is line based, this means that each record consists of one
385 or more lines. A line is terminated by the line feed character 0x0A,
386 commonly written as "\n". In the examples below, this character will be
387 written as "<LF>" ("line feed").
389 After the connection has been established, the client is expected to
390 send a "command". A command consists of the command keyword, possibly
391 some arguments, and a terminating newline character. For a list of
392 commands, see "Valid Commands" below.
394 Example:
396 FLUSH /tmp/foo.rrd<LF>
398 The daemon answers with a line consisting of a status code and a short
399 status message, separated by one or more space characters. A negative
400 status code signals an error, a positive status code or zero signal
401 success. If the status code is greater than zero, it indicates the
402 number of lines that follow the status line.
404 Examples:
406 0 Success<LF>
408 2 Two lines follow<LF>
409 This is the first line<LF>
410 And this is the second line<LF>
413 The following commands are understood by the daemon:
416 Causes the daemon to put _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be to the h\bhe\bea\bad\bd of the update queue
417 (possibly moving it there if the node is already enqueued). The
421 Causes the daemon to start flushing ALL pending values to disk.
422 This returns immediately, even though the writes may take a long
423 time.
426 Shows any "pending" updates for a file, in order. The updates
427 shown have not yet been written to the underlying RRD file.
430 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.
433 Shows the files that are on the output queue. Returns zero or more
434 lines in the following format, where <num_vals> is the number of
435 values to be written for the <file>:
437 <num_vals> <file>
442 Otherwise a short description, possibly containing a pointer to a
443 manual page, is returned. Obviously, this is meant for interactive
444 usage and the format in which the commands and usage summaries are
445 returned is not well defined.
448 Returns a list of metrics which can be used to measure the daemons
449 performance and check its status. For a description of the values
450 returned, see "Performance Values" below.
452 The format in which the values are returned is similar to many
453 other line based protocols: Each value is printed on a separate
454 line, each consisting of the name of the value, a colon, one or
455 more spaces and the actual value.
457 Example:
459 9 Statistics follow
460 QueueLength: 0
461 UpdatesReceived: 30
462 FlushesReceived: 2
463 UpdatesWritten: 13
464 DataSetsWritten: 390
465 TreeNodesNumber: 13
466 TreeDepth: 4
467 JournalBytes: 190
468 JournalRotate: 0
470 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 ...]
472 designed for, so describing the mechanism again is unnecessary.
473 Read "HOW IT WORKS" above for a detailed explanation.
475 Note that rrdcached only accepts absolute timestamps in the update
476 values. Updates strings like "N:1:2:3" are automatically converted
477 to absolute time by the RRD client library before sending to
478 rrdcached.
481 This command is written to the journal after a file is successfully
482 written out to disk. It is used during journal replay to determine
484 journal; it is not accepted from the other command channels.
487 This command initiates the bulk load of multiple commands. This is
488 designed for installations with extremely high update rates, since
492 All commands are executed just as they would be if given
493 individually, except for output to the user. Messages indicating
494 success are suppressed, and error messages are delayed until the
495 client is finished.
497 Command processing is finished when the client sends a dot (".") on
498 its own line. After the client has finished, the server responds
499 with an error count and the list of error messages (if any). Each
500 error messages indicates the number of the command to which it
501 corresponds, and the error message itself. The first user command
504 client: BATCH
505 server: 0 Go ahead. End with dot '.' on its own line.
506 client: UPDATE x.rrd 1223661439:1:2:3 <--- command #1
507 client: UPDATE y.rrd 1223661440:3:4:5 <--- command #2
508 client: and so on...
509 client: .
510 server: 2 Errors
511 server: 1 message for command 1
512 server: 12 message for command 12
515 Disconnect from rrdcached.
520 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)
521 Number of nodes currently enqueued in the update queue.
523 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)
524 Number of UPDATE commands received.
526 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)
527 Number of FLUSH commands received.
529 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)
530 Total number of updates, i. e. calls to "rrd_update_r", since the
531 daemon was started.
533 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)
534 Total number of "data sets" written to disk since the daemon was
536 command. For example: "1223661439:123:456" is one data set with two
537 values. The term "data set" is used to prevent confusion whether
538 individual values or groups of values are counted.
540 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)
541 Number of nodes in the cache.
543 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)
544 Depth of the tree used for fast key lookup.
546 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)
547 Total number of bytes written to the journal since startup.
549 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)
550 Number of times the journal has been rotated since startup.
553 SIGINT and SIGTERM
554 The daemon exits normally on receipt of either of these signals.
556 options.
558 SIGUSR1
559 The daemon exits AFTER flushing all updates out to disk. This may
560 take a while.
562 SIGUSR2
563 The daemon exits immediately, without flushing updates out to disk.
564 Pending updates will be replayed from the journal when the daemon
565 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
566 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.
569 No known bugs at the moment.
572 rrdtool, rrdgraph
575 Florian Forster <octo at verplant.org>
580 kevin brintnall <kbrint@rufus.net>
584 1.4.7 2011-03-15 RRDCACHED(1)