dbpmda(1) — Linux manual page


DBPMDA(1)                  General Commands Manual                 DBPMDA(1)

NAME         top

       dbpmda - debugger for Performance Co-Pilot PMDAs

SYNOPSIS         top

       dbpmda [-efi?]  [-n pmnsfile] [-q timeout] [-U username]

DESCRIPTION         top

       dbpmda is an interactive interface to the interactions between a
       Performance Metric Domain Agent (PMDA(3)) and the Performance Metric
       Collector Daemon (pmcd(1)).  This allows PMDAs to be attached,
       initialized and exercised to test for correctness.

       dbpmda interactively prompts the user for commands, many of which
       emulate the Protocol Data Units (PDUs) that may be sent by a pmcd(1)
       process.  After running dbpmda, enter the command help to get a list
       of the available commands.  The example section below illustrates a
       session using dbpmda to test a PMDA.

       To simplify repetitive testing of a PMDA, the file .dbpmdarc in the
       current working directory can contain a list of commands that will be
       executed by dbpmda on startup, before the user is prompted to enter
       further commands interactively.  While processing the .dbpmdarc file,
       interactive mode and command echoing are enabled and then reset at
       the end of the .dbpmdarc file (see the -i and -e command line options

       The -f command line option prevents startup processing of a .dbpmdarc
       file (if it exists).

       If the system supports readline(3) then this will be used to read
       commands when input is from a tty device, so history and command line
       editing are available.

       As there are no timeout constraints on a PMDA while using dbpmda (as
       compared to pmcd(1)), another debugger like gdb(1) can be used on the
       PMDA process once it has been attached to dbpmda.

OPTIONS         top

       The available command line options are:

       -e, --echo-input
            Echo the input to stdout.  This is useful when the input is
            redirected from a file.

       -f, --norc
            Do not process the .dbpmdarc file.

       -i, --interactive
            Emulate interactive behavior and prompt for new commands, even
            if standard input is not a tty device.

       -n pmnsfile, --namespace=pmnsfile
            Load an alternative Performance Metrics Name Space (PMNS(5))
            from the file pmnsfile.

       -q timeout, --creds-timeout=timeout
            The pmcd to agent version exchange protocol (new in PCP 2.0 -
            introduced to provide backward compatibility) uses this timeout
            to specify how long dbpmda should wait before assuming that no
            version response is coming from an agent.  If this timeout is
            reached, the agent is assumed to be an agent which does not
            understand the PCP 2.0 protocol.  The default timeout interval
            is three seconds, but the -q option allows an alternative
            timeout interval (which must be greater than zero) to be
            specified.  The unit of time is seconds.

       -U username, --username=username
            User account under which to run dbpmda.

       -?, --help
            Display usage message and exit.

EXAMPLES         top

       Below is a dbpmda session using the simple PMDA.  A .dbpmdarc file is
       used to set the debugging option, open the PMDA and display the
       current status of the debugger:

            $ cat .dbpmdarc
            debug libpmda
            open dso pmda_simple.so simple_init 253

       When dbpmda is run, the commands in the .dbpmdarc file are executed

            $ dbpmda
            .dbpmdarc> debug libpmda
            .dbpmdarc> open dso pmda_simple.so simple_init 253
            [Fri Sep 19 10:19:55] dbpmda(11651) Debug: pmdaInit: PMDA simple DSO: Metric 0.0.1(1) matched to indom 253.0(0)
            [Fri Sep 19 10:19:55] dbpmda(11651) Debug: pmdaInit: PMDA simple DSO: help file $PCP_PMDAS_DIR/simple/help opened
            [Fri Sep 19 10:19:55] dbpmda(11651) Info: name        = simple DSO
            [Fri Sep 19 10:19:55] dbpmda(11651) Info: domain      = 253
            [Fri Sep 19 10:19:55] dbpmda(11651) Info: num metrics = 4
            [Fri Sep 19 10:19:55] dbpmda(11651) Info: num indom   = 1
            [Fri Sep 19 10:19:55] dbpmda(11651) Info: direct map  = 1
            .dbpmdarc> status

            Namespace:              (default)
            PMDA:                   ./pmda_simple.so
            Connection:             dso
            DSO Interface Version:  2
            PMDA PMAPI Version:     2
            pmDebug:                32768 ( libpmda )
            Timer:                  off
            Getdesc:                off

            Dump Instance Profile state=INCLUDE, 0 profiles


       To examine the metric and instance descriptors, the desc and instance
       commands can be used.  Metrics may be identified either by name, or
       using the ``dotted'' notation to specify the domain, cluster and item
       fields of a PMID.  Instance domains must be identified using a
       ``dotted'' notation to specify the domain and serial fields.  The
       syntax for most commands will be displayed if the command is given
       without any arguments:

            dbpmda> desc 253.0.0
            PMID: 253.0.0
                Data Type: 32-bit unsigned int  InDom: PM_INDOM_NULL 0xffffffff
                Semantics: instant  Units: none
            dbpmda> instance
            instance indom# [ number | name | "name" ]
            dbpmda> instance 253.0
            pmInDom: 253.0
            [  0] inst: 0 name: "red"
            [  1] inst: 1 name: "green"
            [  2] inst: 2 name: "blue"

       To test the most important component of a PMDA, the fetch, it is
       often useful to determine the time it takes the PMDA to respond.  The
       timer may be turned on before giving a fetch:

            dbpmda> timer on
            dbpmda> fetch simple.numfetch 253.0.1
            PMID(s): 253.0.0 253.0.1
            pmResult dump from 0x100078e0 timestamp: 0.000000 11:00:00.000 numpmid: 2
              253.0.0 (simple.numfetch): numval: 1 valfmt: 0 vlist[]:
               value 1 1.4012985e-45 0x1
              253.0.1 (simple.color): numval: 3 valfmt: 0 vlist[]:
                inst [0 or ???] value 1 1 1.4012985e-45 0x1
                inst [1 or ???] value 101 1.4153114e-43 0x65
                inst [2 or ???] value 201 2.8166099e-43 0xc9
            Timer: 0.003921 seconds
            dbpmda> timer off

       The integer, floating point and hex translations of the values in the
       pmResult structure are dumped if getdesc is set to off (the default).
       Setting getdesc to on would result in only integer values being
       dumped in the above fetch as the descriptor describes the metrics of
       32-bit unsigned integers.

       The simple PMDA also supports the store operation which can be tested
       with subsequent fetch commands:

            dbpmda> store simple.numfetch "42"
            PMID: 253.0.0
            Getting description...
            Getting Result Structure...
            253.0.0: 2 -> 42
            dbpmda> fetch simple.numfetch
            PMID(s): 253.0.0
            pmResult dump from 0x100078e0 timestamp: 0.000000 11:00:00.000 numpmid: 1
              253.0.0 (simple.numfetch): numval: 1 valfmt: 0 vlist[]:
               value 43

       The value argument in the store command must be a string, which is
       enclosed in either single quotes (') or double quotes (").

       A profile can be specified for each instance domain which includes
       all, some or no instances:

            dbpmda> help profile

            profile indom# [ all | none ]
            profile indom# [ add | delete ] number

            For the instance domain specified, the profile may be changed to
            include 'all' instances, no instances, add an instance or delete
            an instance.

            dbpmda> profile 253.0 none
            dbpmda> getdesc on
            dbpmda> fetch 253.0.1
            PMID(s): 253.0.1
            pmResult dump from 0x100078e0 timestamp: 0.000000 11:00:00.000 numpmid: 1
              253.0.1 (simple.color): No values returned!
            dbpmda> profile 253.0 add 2
            dbpmda> fetch 253.0.1
            PMID(s): 253.0.1
            pmResult dump from 0x100078e0 timestamp: 0.000000 11:00:00.000 numpmid: 1
              253.0.1 (simple.color): numval: 1 valfmt: 0 vlist[]:
               value 202
            dbpmda> profile 253.0 add 0
            dbpmda> fetch 253.0.1
            PMID(s): 253.0.1
            pmResult dump from 0x100078e0 timestamp: 0.000000 11:00:00.000 numpmid: 1
              253.0.1 (simple.color): numval: 2 valfmt: 0 vlist[]:
                inst [0 or ???] value 2
                inst [2 or ???] value 203
            dbpmda> status

            PMDA       = pmda_simple.so
            Connection = dso
            pmDebug    = 32768 ( libpmda )
            Timer      = off

            Dump Instance Profile state=INCLUDE, 1 profiles
                    Profile [0] indom=1061158913 [253.0] state=EXCLUDE 2 instances
                            Instances: [2] [0]
            dbpmda> quit

       The watch command (usage: watch filename ) opens an xterm window
       which tails the specified log file.  This window must be closed by
       the user when no longer required.

       The wait command is equivalent to sleep(1) and takes a single integer

       The introduction of dynamic subtrees in the PMNS and PMDA_INTERFACE_4
       in libpcp_pmda has led to additional commands being supported in
       dbpmda to exercise the associated dynamic PMNS services.  The
       examples below are based on the sample PMDA.

            $ dbpmda
            dbpmda> open pipe /var/lib/pcp/pmdas/sample/pmdasample -d 29
            Start pmdasample PMDA: /var/lib/pcp/pmdas/sample/pmdasample -d 29
            dbpmda> children sample.secret
            Metric: sample.secret
               non-leaf foo
                   leaf bar
            dbpmda> traverse sample.secret.foo
            Metric: sample.secret.foo
            dbpmda> pmid sample.secret.foo.bar.four
            Metric: sample.secret.foo.bar.four
            dbpmda> name 29.0.1006
            PMID: 29.0.1006

       The children command returns the next name component for all the
       direct descendants of a node within a dynamic subtree of the PMNS.
       The related traverse command returns the full metric names for all
       leaf nodes in the PMNS below the specified non-leaf node in a dynamic
       subtree of the PMNS.

       The name and pmid commands exercise the translation of metric names
       to PMIDs (and vice versa) for metrics within a dynamic subtree of the

       If the commands children, traverse, pmid or name are used with a PMDA
       that is not using PMDA_INTERFACE_4 or with performance metric names
       that are not part of a dynamic subtree of the PMNS, then the PMDA
       would be expected to return errors (PM_ERR_NAME or PM_ERR_PMID) to
       reflect the fact that the operation is in error (outside a dynamic
       subtree of the PMNS it is pmcd(1) and not the PMDA that is
       responsible for implementing these functions).

       Client authentication mechanisms have been incorporated into the
       PMCS, providing per-user (and per-connection) information that is
       available to PMDAs.  A PMDA using PMDA_INTERFACE_6 or later in
       libpcp_pmda is able to make use of the "attribute" method to gain
       visibility into these authenticated connections, with access to
       information including user and group identifiers, user name, and so
       on.  The need to exercise and debug this interface has led to a new
       dbpmda command.  The following example is based on the sample PMDA.

            $ dbpmda
            dbpmda> open pipe pmdasample -D AUTH -l logfile
            Start pmdasample PMDA: pmdasample -D AUTH -l logfile
            dbpmda> attr "username" "tanya"
            Attribute: username=tanya
            dbpmda> attr 11 "0"
            Attribute: userid=0

       The attr command passes connection attributes (PCP_ATTR keys) and
       their values into a PMDA in much the same way that PMCD would for a
       client connection.  dbpmda always passes a client context identifier
       of zero, and while no validity checking on values is performed only
       recognised attributes can be set.

       In the example above the AUTH debugging option is set for the PMDA,
       which uses this in its attribute callback and records each attribute
       and value pair sent to it in its logfile.

       Note that authentication checks have already been performed by PMCD
       by the time a PMDA is presented with these attributes, so no further
       verification is necessary by the PMDA.

CAVEATS         top

       A value cannot be stored into metrics of type PM_TYPE_AGGREGATE or

       dbpmda uses fork(2) and exec(2) to attach to daemon PMDAs.  dbpmda
       makes no attempt to detect the termination of the daemon PMDA
       process, so it is possible for a PMDA to exit unexpectedly without
       any notification.  However, any further communication attempts with
       the PMDA will result in errors which will indicate that the PMDA is
       no longer responding.

FILES         top

            List of commands to do on startup.


       Environment variables with the prefix PCP_ are used to parameterize
       the file and directory names used by PCP.  On each installation, the
       file /etc/pcp.conf contains the local values for these variables.
       The $PCP_CONF variable may be used to specify an alternative
       configuration file, as described in pcp.conf(5).

       For environment variables affecting PCP tools, see pmGetOptions(3).

SEE ALSO         top

       gdb(1), pmcd(1), pmdbg(1), exec(2), fork(2), PMAPI(3), PMDA(3),
       pcp.conf(5), pcp.env(5) and PMNS(5).

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.
       Information about the project can be found at ⟨http://www.pcp.io/⟩.
       If you have a bug report for this manual page, send it to
       pcp@groups.io.  This page was obtained from the project's upstream
       Git repository ⟨https://github.com/performancecopilot/pcp.git⟩ on
       2020-08-13.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-08-11.)  If you discover any
       rendering problems in this HTML version of the page, or you believe
       there is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

Performance Co-Pilot                 PCP                           DBPMDA(1)

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