'\"macro stdmacro
.\"
.\" Copyright (c) 2012 Red Hat.
.\" Copyright (c) 2012 Nathan Scott.  All Rights Reserved.
.\" 
.\" This program is free software; you can redistribute it and/or modify it
.\" under the terms of the GNU General Public License as published by the
.\" Free Software Foundation; either version 2 of the License, or (at your
.\" option) any later version.
.\" 
.\" This program is distributed in the hope that it will be useful, but
.\" WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
.\" or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
.\" for more details.
.\" 
.\"
.TH PMDABASH 1 "PCP" "Performance Co-Pilot"
.SH NAME
\f3pmdabash\f1 \- Bourne-Again SHell trace performance metrics domain agent
.SH SYNOPSIS
\f3$PCP_PMDAS_DIR/bash/pmdabash\f1
[\f3\-C\f1]
[\f3\-d\f1 \f2domain\f1]
[\f3\-l\f1 \f2logfile\f1]
[\f3\-I\f1 \f2interval\f1]
[\f3\-t\f1 \f2timeout\f1]
[\f3\-U\f1 \f2username\f1]
\f2configfile\f1
.br
.SH DESCRIPTION
.B pmdabash
is an experimental Performance Metrics Domain Agent (PMDA) which
exports "xtrace" events from a traced
.BR bash (1)
process.
This includes the command execution information that would
usually be sent to standard error with the
.BR "set -x"
option to the shell.
.PP
Event metrics are exported showing each command executed, the
function name and line number in the script, and a timestamp.
Additionally, the process identifier for the shell and its parent
process are exported.
.PP
This requires
.B bash
version 4 or later.
.PP
A brief description of the
.B pmdabash
command line options follows:
.TP 5
.B \-d
It is absolutely crucial that the performance metrics
.I domain
number specified here is unique and consistent.
That is,
.I domain
should be different for every PMDA on the one host, and the same
.I domain
number should be used for the same PMDA on all hosts.
.TP 5
.B \-l
Location of the log file.  By default, a log file named
.I bash.log
is written in the current directory of
.BR pmcd (1)
when
.B pmdabash
is started, i.e.
.BR $PCP_LOG_DIR/pmcd .
If the log file cannot
be created or is not writable, output is written to the standard error instead.
.TP 5
.B \-s
Amount of time (in seconds) between subsequent evaluations of the shell
trace file descriptor(s).
The default is 2 seconds.
.PP
.TP 5
.B \-m
Maximum amount of memory to be allowed for each event queue (one per traced process).
The default is 2 megabytes.
.TP 5
.B \-U
User account under which to run the agent.
The default is the unprivileged "pcp" account in current versions of PCP,
but in older versions the superuser account ("root") was used by default.
.PP
.SH INSTALLATION
In order for a host to export the names, help text and values for the bash
performance metrics, do the following as root:
.PP
.ft CW
.nf
.in +0.5i
# cd $PCP_PMDAS_DIR/bash
# ./Install
.in
.fi
.ft 1
.PP
As soon as an instrumented shell script (see INSTRUMENTATION selection below) is
run, with tracing enabled, new metric values will appear - no further setup of the
agent is required.
.PP
If you want to undo the installation, do the following as root:
.PP
.ft CW
.nf
.in +0.5i
# cd $PCP_PMDAS_DIR/bash
# ./Remove
.in
.fi
.ft 1
.PP
.B pmdabash
is launched by
.BR pmcd (1)
and should never be executed directly.
The Install and Remove scripts notify
.BR pmcd (1)
when the agent is installed or removed.
.SH INSTRUMENTATION
In order to allow the flow of event data between a
.BR bash (1)
script and
.BR pmdabash ,
the script should take the following actions:
.PP
.ft CW
.nf
.in +0.5i
#!/bin/sh
source $PCP_DIR/etc/pcp.sh

pcp_trace on $@       # enable tracing
echo "awoke, $count"

pcp_trace off         # disable tracing
.in
.fi
.ft 1
.PP
The tracing can be enabled and disabled any number of times by the script.
On successful installation of the agent, several metrics will be available:
.PP
.ft CW
.nf
.in +0.5i
$ pminfo bash
bash.xtrace.numclients
bash.xtrace.maxmem
bash.xtrace.queuemem
bash.xtrace.count
bash.xtrace.records
bash.xtrace.parameters.pid
bash.xtrace.parameters.parent
bash.xtrace.parameters.lineno
bash.xtrace.parameters.function
bash.xtrace.parameters.command
.in
.fi
.ft 1
.PP
When an instrumented script is running, the generation of event records
can be verified using the
.BR pmevent (1)
command, as follows:
.PP
.ft CW
.nf
.in +0.5i
$ pmevent \-t 1 \-x '' bash.xtrace.records
host:      localhost
samples:   all
bash.xtrace.records["4538 ./test-trace.sh 1 2 3"]: 5 event records
  10:00:05.000 --- event record [0] flags 0x19 (point,id,parent) ---
    bash.xtrace.parameters.pid 4538
    bash.xtrace.parameters.parent 4432
    bash.xtrace.parameters.lineno 43
    bash.xtrace.parameters.command "true"
  10:00:05.000 --- event record [1] flags 0x19 (point,id,parent) ---
    bash.xtrace.parameters.pid 4538
    bash.xtrace.parameters.parent 4432
    bash.xtrace.parameters.lineno 45
    bash.xtrace.parameters.command "((  count++  ))"
  10:00:05.000 --- event record [2] flags 0x19 (point,id,parent) ---
    bash.xtrace.parameters.pid 4538
    bash.xtrace.parameters.parent 4432
    bash.xtrace.parameters.lineno 46
    bash.xtrace.parameters.command "echo 'awoke, 3'"
  10:00:05.000 --- event record [3] flags 0x19 (point,id,parent) ---
    bash.xtrace.parameters.pid 4538
    bash.xtrace.parameters.parent 4432
    bash.xtrace.parameters.lineno 47
    bash.xtrace.parameters.command "tired 2"
  10:00:05.000 --- event record [4] flags 0x19 (point,id,parent) ---
    bash.xtrace.parameters.pid 4538
    bash.xtrace.parameters.parent 4432
    bash.xtrace.parameters.lineno 38
    bash.xtrace.parameters.function "tired"
    bash.xtrace.parameters.command "sleep 2"
.in
.fi
.ft 1
.SH FILES
.PD 0
.TP 10
.B $PCP_PMCDCONF_PATH
command line options used to launch
.B pmdabash
.TP 10
.B $PCP_PMDAS_DIR/bash/help
default help text file for the bash metrics
.TP 10
.B $PCP_PMDAS_DIR/bash/Install
installation script for the
.B pmdabash
agent
.TP 10
.B $PCP_PMDAS_DIR/bash/Remove
undo installation script for
.B pmdabash
.TP 10
.B $PCP_LOG_DIR/pmcd/bash.log
default log file for error messages and other information from
.B pmdabash
.PD
.SH "PCP ENVIRONMENT"
Environment variables with the prefix
.B PCP_
are used to parameterize the file and directory names
used by PCP.
On each installation, the file
.B /etc/pcp.conf
contains the local values for these variables.
The
.B $PCP_CONF
variable may be used to specify an alternative
configuration file,
as described in
.BR pcp.conf (5).
.SH SEE ALSO
.BR bash (1),
.BR pmevent (1)
and
.BR pmcd (1).