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dbpmda

NAME

dbpmda - debugger for Performance Co-Pilot PMDAs

SYNOPSIS

$PCP_BINADM_DIR/dbpmda [-ei] [-n pmnsfile] [-q timeout]

DESCRIPTION

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 arguments below).

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.

dbpmda accepts the following command line arguments:

-e

Echo the input to stdout. This is useful when the input is redirected from a file.

-i

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

-n pmnsfile

Normally dbpmda operates on the distributed Performance Metrics Name Space (PMNS), however if the -n option is specified an alternative local PMNS is loaded from the file pmnsfile.

-q 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 five 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.

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

EXAMPLE

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

 $ cat .dbpmdarc
 debug libpmda
 open dso mips_o32.pmda_simple.so simple_init 253
 status
 

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

 $ dbpmda
 .dbpmdarc> debug libpmda
 .dbpmdarc> open dso mips_o32.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:                   ./mips_o32.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
 
 .dbpmdarc>
 

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
 

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       = mips_o32.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 xwsh 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 argument.

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
 dbpmda> 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
    sample.secret.foo.bar.max.redirect
    sample.secret.foo.one
    sample.secret.foo.two
    sample.secret.foo.bar.three
    sample.secret.foo.bar.four
    sample.secret.foo.bar.grunt.five
    sample.secret.foo.bar.grunt.snort.six
    sample.secret.foo.bar.grunt.snort.huff.puff.seven
 dbpmda> pmid sample.secret.foo.bar.four
 Metric: sample.secret.foo.bar.four
    29.0.1004
 dbpmda> name 29.0.1006
 PMID: 29.0.1006
    sample.secret.foo.bar.grunt.snort.six
 

The children command returns the next name component for all the direct descendents 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 PMNS.

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).

CAVEATS

A value cannot be stored into a metric of type PM_TYPE_AGGREGATE.

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.

Only DSO PMDAs with the same simabi (Subprogram Interface Model ABI) as the running kernel may be attached to dbpmda. ie. a machine running a 64-bit kernel will have a 64-bit version of dbpmda which may only be attached to 64-bit DSO PMDAs. As daemon PMDAs are separate processes, there are no simabi restrictions between dbpmda and daemon PMDAs.

FILES

./.dbpmdarc

List of commands to do on startup.

PCP ENVIRONMENT

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(4).

SEE ALSO

pmcd(1), pmdbg(1), exec(2), fork(2), PMAPI(3), PMDA(3), pcp.conf(4) and pcp.env(4).