RRDCACHED(1)                        rrdtool                       RRDCACHED(1)



NNAAMMEE
       rrdcached - Data caching daemon for rrdtool

SSYYNNOOPPSSIISS
       rrrrddccaacchheedd [--PP _p_e_r_m_i_s_s_i_o_n_s] [--ll _a_d_d_r_e_s_s] [--ss _g_r_o_u_p] [--ww _t_i_m_e_o_u_t]
       [--zz _d_e_l_a_y] [--ff _t_i_m_e_o_u_t] [--pp _p_i_d___f_i_l_e] [--tt _w_r_i_t_e___t_h_r_e_a_d_s]
       [--jj _j_o_u_r_n_a_l___d_i_r] [-F] [-g] [--bb _b_a_s_e___d_i_r [--BB]]

DDEESSCCRRIIPPTTIIOONN
       rrrrddccaacchheedd is a daemon that receives updates to existing RRD files,
       accumulates them and, if enough have been received or a defined time
       has passed, writes the updates to the RRD file. A _f_l_u_s_h command may be
       used to force writing of values to disk, so that graphing facilities
       and similar can work with up-to-date data.

       The daemon was written with big setups in mind. Those setups usually
       run into IO related problems sooner or later for reasons that are
       beyond the scope of this document. Check the wiki at the RRDtool
       homepage for details. Also check "SECURITY CONSIDERATIONS" below before
       using this daemon! A detailed description of how the daemon operates
       can be found in the "HOW IT WORKS" section below.

OOPPTTIIOONNSS
       --ll _a_d_d_r_e_s_s
           Tells the daemon to bind to _a_d_d_r_e_s_s and accept incoming connections
           on that socket. If _a_d_d_r_e_s_s begins with "unix:", everything
           following that prefix is interpreted as the path to a UNIX domain
           socket. Otherwise the address or node name are resolved using
           "getaddrinfo()".

           For network sockets, a port may be specified by using the form
           "[[_a_d_d_r_e_s_s]]::_p_o_r_t_". If the address is an IPv4 address or a fully
           qualified domain name (i. e. the address contains at least one dot
           (".")), the square brackets can be omitted, resulting in the
           (simpler) "_a_d_d_r_e_s_s::_p_o_r_t_" pattern. The default port is 4422221177//ttccpp. If
           you specify a network socket, it is mandatory to read the "SECURITY
           CONSIDERATIONS" section.

           The following formats are accepted. Please note that the address of
           the UNIX domain socket mmuusstt start with a slash in the second case!

              unix:</path/to/unix.sock>
              /<path/to/unix.sock>
              <hostname-or-ip>
              [<hostname-or-ip>]:<port>
              <hostname-or-ipv4>:<port>

           If the --ll option is not specified the default address,
           "unix:/tmp/rrdcached.sock", will be used.

       --ss _g_r_o_u_p___n_a_m_e|_g_i_d
           Set the group permissions of a UNIX domain socket. The option
           accepts either a numeric group id or group name. That group will
           then have both read and write permissions (the socket will have
           file permissions 0750) for the socket and, therefore, is able to
           send commands to the daemon. This may be useful in cases where you
           cannot easily run all RRD processes with the same user privileges
           (e.g. graph generating CGI scripts that typically run in the
           permission context of the web server).

           This option affects the _f_o_l_l_o_w_i_n_g UNIX socket addresses (the
           following --ll options) or the default socket (if no --ll options have
           been specified), i.e., you may specify different settings for
           different sockets.

           The default is not to change ownership or permissions of the socket
           and, thus, use the system default.

       --mm _m_o_d_e
           Set the file permissions of a UNIX domain socket. The option
           accepts an octal number representing the bit pattern for the mode
           (see _c_h_m_o_d(1) for details).

           Please note that not all systems honor this setting. On Linux,
           read/write permissions are required to connect to a UNIX socket.
           However, many BSD-derived systems ignore permissions for UNIX
           sockets. See _u_n_i_x(7) for details.

           This option affects the _f_o_l_l_o_w_i_n_g UNIX socket addresses (the
           following --ll options) or the default socket (if no --ll options have
           been specified), i.e., you may specify different settings for
           different sockets.

           The default is not to change ownership or permissions of the socket
           and, thus, use the system default.

       --PP _c_o_m_m_a_n_d[,_c_o_m_m_a_n_d[,...]]
           Specifies the commands accepted via a network socket. This allows
           administrators of _R_R_D_C_a_c_h_e_D to control the actions accepted from
           various sources.

           The arguments given to the --PP option is a comma separated list of
           commands.  For example, to allow the "FLUSH" and "PENDING" commands
           one could specify:

             rrdcached -P FLUSH,PENDING $MORE_ARGUMENTS

           The --PP option affects the _f_o_l_l_o_w_i_n_g socket addresses (the following
           --ll options) or the default socket (if no --ll options have been
           specified). In the following example, only the IPv4 network socket
           (address 10.0.0.1) will be restricted to the "FLUSH" and "PENDING"
           commands:

             rrdcached -l unix:/some/path -P FLUSH,PENDING -l 10.0.0.1

           A complete list of available commands can be found in the section
           "Valid Commands" below. There are two minor special exceptions:

           +o   The "HELP" and "QUIT" commands are always allowed.

           +o   If the "BATCH" command is accepted, the .. command will
               automatically be accepted, too.

           Please also read "SECURITY CONSIDERATIONS" below.

       --ww _t_i_m_e_o_u_t
           Data is written to disk every _t_i_m_e_o_u_t seconds. If this option is
           not specified the default interval of 300 seconds will be used.

       --zz _d_e_l_a_y
           If specified, rrdcached will delay writing of each RRD for a random
           number of seconds in the range [0,_d_e_l_a_y).  This will avoid too many
           writes being queued simultaneously.  This value should be no
           greater than the value specified in --ww.  By default, there is no
           delay.

       --ff _t_i_m_e_o_u_t
           Every _t_i_m_e_o_u_t seconds the entire cache is searched for old values
           which are written to disk. This only concerns files to which
           updates have stopped, so setting this to a high value, such as
           3600 seconds, is acceptable in most cases. This timeout defaults to
           3600 seconds.

       --pp _f_i_l_e
           Sets the name and location of the PID-file. If not specified, the
           default, "_$_l_o_c_a_l_s_t_s_t_e_d_i_r_/_r_u_n_/_r_r_d_c_a_c_h_e_d_._p_i_d_" will be used.

       --tt _w_r_i_t_e___t_h_r_e_a_d_s
           Specifies the number of threads used for writing RRD files.  The
           default is 4.  Increasing this number will allow rrdcached to have
           more simultaneous I/O requests into the kernel.  This may allow the
           kernel to re-order disk writes, resulting in better disk
           throughput.

       --jj _d_i_r
           Write updates to a journal in _d_i_r.  In the event of a program or
           system crash, this will allow the daemon to write any updates that
           were pending at the time of the crash.

           On startup, the daemon will check for journal files in this
           directory.  If found, all updates therein will be read into memory
           before the daemon starts accepting new connections.

           The journal will be rotated with the same frequency as the flush
           timer given by --ff.

           When journaling is enabled, the daemon will use a fast shutdown
           procedure.  Rather than flushing all files to disk, it will make
           sure the journal is properly written and exit immediately.
           Although the RRD data files are not fully up-to-date, no
           information is lost; all pending updates will be replayed from the
           journal next time the daemon starts up.

           To disable fast shutdown, use the --FF option.

       --FF  ALWAYS flush all updates to the RRD data files when the daemon is
           shut down, regardless of journal setting.

       --gg  Run in the foreground.  The daemon will not _f_o_r_k_(_).

       --bb _d_i_r
           The daemon will change into a specific directory at startup. All
           files passed to the daemon, that are specified by a rreellaattiivvee path,
           will be interpreted to be relative to this directory. If not given
           the default, "/tmp", will be used.

             +------------------------+------------------------+
             ! Command line           ! File updated           !
             +------------------------+------------------------+
             ! foo.rrd                ! /tmp/foo.rrd           !
             ! foo/bar.rrd            ! /tmp/foo/bar.rrd       !
             ! /var/lib/rrd/foo.rrd   ! /var/lib/rrd/foo.rrd   !
             +------------------------+------------------------+
             Paths given on the command  line and paths actually
             updated by the daemon,  assuming the base directory
             "/tmp".

           WWAARRNNIINNGG:: The paths up to and including the base directory MMUUSSTT NNOOTT
           BBEE symbolic links.  In other words, if the base directory is
           specified as:

               -b /base/dir/somewhere

           ... then NNOONNEE of the following should be symbolic links:

               /base
               /base/dir
               /base/dir/somewhere

       --BB  Only permit writes into the base directory specified in --bb (and any
           sub-directories).  This does NNOOTT detect symbolic links.  Paths
           containing "../" will also be blocked.

AAFFFFEECCTTEEDD RRRRDDTTOOOOLL CCOOMMMMAANNDDSS
       The following commands may be made aware of the rrrrddccaacchheedd using the
       command line argument ----ddaaeemmoonn or the environment variable
       RRRRDDCCAACCHHEEDD__AADDDDRREESSSS:

       +o   dump

       +o   fetch

       +o   flush

       +o   graph

       +o   graphv

       +o   info

       +o   last

       +o   lastupdate

       +o   update

       +o   xport

       The uuppddaattee command can send values to the daemon instead of writing
       them to the disk itself. All other commands can send a FFLLUUSSHH command
       (see below) to the daemon before accessing the files, so they work with
       up-to-date data even if the cache timeout is large.

EERRRROORR RREEPPOORRTTIINNGG
       The daemon reports errors in one of two ways: During startup, error
       messages are printed to "STDERR". One of the steps when starting up is
       to fork to the background and closing "STDERR" - after this writing
       directly to the user is no longer possible. Once this has happened, the
       daemon will send log messages to the system logging daemon using
       _s_y_s_l_o_g(3). The facility used is "LOG_DAEMON".

HHOOWW IITT WWOORRKKSS
       When receiving an update, rrrrddccaacchheedd does not write to disk but looks
       for an entry for that file in its internal tree. If not found, an entry
       is created including the current time (called "First" in the diagram
       below). This time is nnoott the time specified on the command line but the
       time the operating system considers to be "now". The value and time of
       the value (called "Time" in the diagram below) are appended to the tree
       node.

       When appending a value to a tree node, it is checked whether it's time
       to write the values to disk. Values are written to disk if
       "now() - First >= timeout", where "timeout" is the timeout specified
       using the --ww option, see "OPTIONS". If the values are "old enough" they
       will be enqueued in the "update queue", i. e. they will be appended to
       the linked list shown below.  Because the tree nodes and the elements
       of the linked list are the same data structures in memory, any update
       to a file that has already been enqueued will be written with the next
       write to the RRD file, too.

       A separate "update thread" constantly dequeues the first element in the
       update queue and writes all its values to the appropriate file. So as
       long as the update queue is not empty files are written at the highest
       possible rate.

       Since the timeout of files is checked only when new values are added to
       the file, "dead" files, i. e. files that are not updated anymore, would
       never be written to disk. Therefore, every now and then, controlled by
       the --ff option, the entire tree is walked and all "old" values are
       enqueued. Since this only affects "dead" files and walking the tree is
       relatively expensive, you should set the "flush interval" to a
       reasonably high value. The default is 3600 seconds (one hour).

       The downside of caching values is that they won't show up in graphs
       generated from the RRD files. To get around this, the daemon provides
       the "flush command" to flush specific files. This means that the file
       is inserted at the hheeaadd of the update queue or moved there if it is
       already enqueued. The flush command will return only after the file's
       pending updates have been written to disk.

        +------+   +------+                               +------+
        ! head !   ! root !                               ! tail !
        +---+--+   +---+--+                               +---+--+
            !         /\                                      !
            !        /  \                                     !
            !       /\  /\                                    !
            !      /\/\ \ `----------------- ... --------,    !
            V     /      `-------,                       !    V
        +---+----+---+    +------+-----+             +---+----+---+
        ! File:  foo !    ! File:  bar !             ! File:  qux !
        ! First: 101 !    ! First: 119 !             ! First: 180 !
        ! Next:&bar -+--->! Next:&... -+---> ... --->! Next:NULL  !
        | Prev:NULL  !<---+-Prev:&foo  !<--- ... ----+-Prev: &... !
        +============+    +============+             +============+
        ! Time:  100 !    ! Time:  120 !             ! Time:  180 !
        ! Value:  10 !    ! Value: 0.1 !             ! Value: 2,2 !
        +------------+    +------------+             +------------+
        ! Time:  110 !    ! Time:  130 !             ! Time:  190 !
        ! Value:  26 !    ! Value: 0.1 !             ! Value: 7,3 !
        +------------+    +------------+             +------------+
        :            :    :            :             :            :
        +------------+    +------------+             +------------+
        ! Time:  230 !    ! Time:  250 !             ! Time:  310 !
        ! Value:  42 !    ! Value: 0.2 !             ! Value: 1,2 !
        +------------+    +------------+             +------------+

       The above diagram demonstrates:

       +o   Files/values are stored in a (balanced) tree.

       +o   Tree nodes and entries in the update queue are the same data
           structure.

       +o   The local time ("First") and the time specified in updates ("Time")
           may differ.

       +o   Timed out values are inserted at the "tail".

       +o   Explicitly flushed values are inserted at the "head".

       +o   ASCII art rocks.

SSEECCUURRIITTYY CCOONNSSIIDDEERRAATTIIOONNSS
   AAuutthheennttiiccaattiioonn
       If your rrdtool installation was built without libwrap there is no form
       of authentication for clients connecting to the rrdcache daemon!

       If your rrdtool installation was built with libwrap then you can use
       hosts_access to restrict client access to the rrdcache daemon
       (rrdcached).  For more information on how to use hosts_access to
       restrict access to the rrdcache daemon you should read the
       _h_o_s_t_s___a_c_c_e_s_s(5) man pages.

       It is still highly recommended to install a packet filter or similar
       mechanism to prevent unauthorized connections. Unless you have a
       dedicated VLAN or VPN for this, using network sockets is probably a bad
       idea!

   AAuutthhoorriizzaattiioonn
       There is minimal per-socket authorization.

       Authorization is currently done on a per-socket basis. That means each
       socket has a list of commands it will accept and it will accept. It
       will accept only those commands explicitly listed but it will
       (currently) accept these commands from anyone reaching the socket.

       If the networking sockets are to be used, it is necessary to restrict
       the accepted commands to those needed by external clients. If, for
       example, external clients want to draw graphs of the cached data, they
       should only be allowed to use the "FLUSH" command.

       Authorization does not work when rrcached is socket-activated by
       systemd.

   EEnnccrryyppttiioonn
       There is no encryption.

       Again, this may be added in the future, but for the time being it is
       your job to keep your private data private. Install a VPN or an
       encrypted tunnel if you statistics are confidential!

   SSaanniittyy cchheecckkiinngg
       There is no sanity checking.

       The daemon will blindly write to any file it gets told, so you really
       should create a separate user just for this daemon. Also it does not do
       any sanity checks, so if it gets told to write values for a time far in
       the future, your files will be messed up good!

   CCoonncclluussiioonn
       +o   Security is the job of the administrator.

       +o   We recommend to allow write access via UNIX domain sockets only.

       +o   You have been warned.

PPRROOTTOOCCOOLL
       The daemon communicates with clients using a line based ASCII protocol
       which is easy to read and easy to type. This makes it easy for scripts
       to implement the protocol and possible for users to use telnet to
       connect to the daemon and test stuff "by hand".

       The protocol is line based, this means that each record consists of one
       or more lines. A line is terminated by the line feed character 0x0A,
       commonly written as "\n". In the examples below, this character will be
       written as "<LF>" ("line feed").

       After the connection has been established, the client is expected to
       send a "command". A command consists of the command keyword, possibly
       some arguments, and a terminating newline character. For a list of
       commands, see "Valid Commands" below.

       Example:

         FLUSH /tmp/foo.rrd<LF>

       The daemon answers with a line consisting of a status code and a short
       status message, separated by one or more space characters. A negative
       status code signals an error, a positive status code or zero signal
       success. If the status code is greater than zero, it indicates the
       number of lines that follow the status line.

       Examples:

        0 Success<LF>

        2 Two lines follow<LF>
        This is the first line<LF>
        And this is the second line<LF>

   VVaalliidd CCoommmmaannddss
       The following commands are understood by the daemon:

       FFLLUUSSHH _f_i_l_e_n_a_m_e
           Causes the daemon to put _f_i_l_e_n_a_m_e to the hheeaadd of the update queue
           (possibly moving it there if the node is already enqueued). The
           answer will be sent aafftteerr the node has been dequeued.

       FFLLUUSSHHAALLLL
           Causes the daemon to start flushing ALL pending values to disk.
           This returns immediately, even though the writes may take a long
           time.

       PPEENNDDIINNGG _f_i_l_e_n_a_m_e
           Shows any "pending" updates for a file, in order.  The updates
           shown have not yet been written to the underlying RRD file.

       FFOORRGGEETT _f_i_l_e_n_a_m_e
           Removes _f_i_l_e_n_a_m_e from the cache.  Any pending updates WWIILLLL BBEE LLOOSSTT.

       QQUUEEUUEE
           Shows the files that are on the output queue.  Returns zero or more
           lines in the following format, where <num_vals> is the number of
           values to be written for the <file>:

               <num_vals> <file>

       HHEELLPP [_c_o_m_m_a_n_d]
           Returns a short usage message. If no command is given, or _c_o_m_m_a_n_d
           is HHEELLPP, a list of commands supported by the daemon is returned.
           Otherwise a short description, possibly containing a pointer to a
           manual page, is returned.  Obviously, this is meant for interactive
           usage and the format in which the commands and usage summaries are
           returned is not well defined.

       SSTTAATTSS
           Returns a list of metrics which can be used to measure the daemons
           performance and check its status. For a description of the values
           returned, see "Performance Values" below.

           The format in which the values are returned is similar to many
           other line based protocols: Each value is printed on a separate
           line, each consisting of the name of the value, a colon, one or
           more spaces and the actual value.

           Example:

            9 Statistics follow
            QueueLength: 0
            UpdatesReceived: 30
            FlushesReceived: 2
            UpdatesWritten: 13
            DataSetsWritten: 390
            TreeNodesNumber: 13
            TreeDepth: 4
            JournalBytes: 190
            JournalRotate: 0

       UUPPDDAATTEE _f_i_l_e_n_a_m_e _v_a_l_u_e_s [_v_a_l_u_e_s ...]
           Adds more data to a filename. This is tthhee operation the daemon was
           designed for, so describing the mechanism again is unnecessary.
           Read "HOW IT WORKS" above for a detailed explanation.

           Note that rrdcached only accepts absolute timestamps in the update
           values.  Updates strings like "N:1:2:3" are automatically converted
           to absolute time by the RRD client library before sending to
           rrdcached.

       WWRROOTTEE _f_i_l_e_n_a_m_e
           This command is written to the journal after a file is successfully
           written out to disk.  It is used during journal replay to determine
           which updates have already been applied.  It is _o_n_l_y valid in the
           journal; it is not accepted from the other command channels.

       BBAATTCCHH
           This command initiates the bulk load of multiple commands.  This is
           designed for installations with extremely high update rates, since
           it permits more than one command to be issued per _r_e_a_d_(_) and
           _w_r_i_t_e_(_).

           All commands are executed just as they would be if given
           individually, except for output to the user.  Messages indicating
           success are suppressed, and error messages are delayed until the
           client is finished.

           Command processing is finished when the client sends a dot (".") on
           its own line.  After the client has finished, the server responds
           with an error count and the list of error messages (if any).  Each
           error messages indicates the number of the command to which it
           corresponds, and the error message itself.  The first user command
           after BBAATTCCHH is command number one.

               client:  BATCH
               server:  0 Go ahead.  End with dot '.' on its own line.
               client:  UPDATE x.rrd 1223661439:1:2:3            <--- command #1
               client:  UPDATE y.rrd 1223661440:3:4:5            <--- command #2
               client:  and so on...
               client:  .
               server:  2 Errors
               server:  1 message for command 1
               server:  12 message for command 12

       QQUUIITT
           Disconnect from rrdcached.

   PPeerrffoorrmmaannccee VVaalluueess
       The following counters are returned by the SSTTAATTSS command:

       QQuueeuueeLLeennggtthh _(_u_n_s_i_g_n_e_d _6_4_b_i_t _i_n_t_e_g_e_r_)
           Number of nodes currently enqueued in the update queue.

       UUppddaatteessRReecceeiivveedd _(_u_n_s_i_g_n_e_d _6_4_b_i_t _i_n_t_e_g_e_r_)
           Number of UPDATE commands received.

       FFlluusshheessRReecceeiivveedd _(_u_n_s_i_g_n_e_d _6_4_b_i_t _i_n_t_e_g_e_r_)
           Number of FLUSH commands received.

       UUppddaatteessWWrriitttteenn _(_u_n_s_i_g_n_e_d _6_4_b_i_t _i_n_t_e_g_e_r_)
           Total number of updates, i. e. calls to "rrd_update_r", since the
           daemon was started.

       DDaattaaSSeettssWWrriitttteenn _(_u_n_s_i_g_n_e_d _6_4_b_i_t _i_n_t_e_g_e_r_)
           Total number of "data sets" written to disk since the daemon was
           started. A data set is one or more values passed to the UUPPDDAATTEE
           command. For example: "1223661439:123:456" is one data set with two
           values. The term "data set" is used to prevent confusion whether
           individual values or groups of values are counted.

       TTrreeeeNNooddeessNNuummbbeerr _(_u_n_s_i_g_n_e_d _6_4_b_i_t _i_n_t_e_g_e_r_)
           Number of nodes in the cache.

       TTrreeeeDDeepptthh _(_u_n_s_i_g_n_e_d _6_4_b_i_t _i_n_t_e_g_e_r_)
           Depth of the tree used for fast key lookup.

       JJoouurrnnaallBByytteess _(_u_n_s_i_g_n_e_d _6_4_b_i_t _i_n_t_e_g_e_r_)
           Total number of bytes written to the journal since startup.

       JJoouurrnnaallRRoottaattee _(_u_n_s_i_g_n_e_d _6_4_b_i_t _i_n_t_e_g_e_r_)
           Number of times the journal has been rotated since startup.

SSIIGGNNAALLSS
       SIGINT and SIGTERM
           The daemon exits normally on receipt of either of these signals.
           Pending updates are handled in accordance with the --jj and --FF
           options.

       SIGUSR1
           The daemon exits AFTER flushing all updates out to disk.  This may
           take a while.

       SIGUSR2
           The daemon exits immediately, without flushing updates out to disk.
           Pending updates will be replayed from the journal when the daemon
           starts up again.  WWAARRNNIINNGG:: iiff jjoouurrnnaalliinngg ((--jj)) iiss NNOOTT eennaabblleedd,, aannyy
           ppeennddiinngg uuppddaatteess WWIILLLL BBEE LLOOSSTT.

BBUUGGSS
       No known bugs at the moment.

SSEEEE AALLSSOO
       rrdtool, rrdgraph

AAUUTTHHOORR
       Florian Forster <octo at verplant.org>

       Both rrrrddccaacchheedd and this manual page have been written by Florian.

CCOONNTTRRIIBBUUTTOORRSS
       kevin brintnall <kbrint@rufus.net>



1.4.8                             2014-01-08                      RRDCACHED(1)
