PMDABASH(1)PMDABASH(1)NAMEpmdabash - Bourne-Again SHell trace performance metrics domain agent
SYNOPSIS
$PCP_PMDAS_DIR/bash/pmdabash [-C] [-d domain] [-l logfile] [-I inter‐
val] [-t timeout] configfile
DESCRIPTIONpmdabash is an experimental Performance Metrics Domain Agent (PMDA)
which exports "xtrace" events from a traced bash(1) process. This
includes the command execution information that would usually be sent
to standard error with the set -x option to the shell.
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.
This requires bash version 4 or later.
A brief description of the pmdabash command line options follows:
-d It is absolutely crucial that the performance metrics domain num‐
ber specified here is unique and consistent. That is, domain
should be different for every PMDA on the one host, and the same
domain number should be used for the same PMDA on all hosts.
-l Location of the log file. By default, a log file named bash.log
is written in the current directory of pmcd(1) when pmdabash is
started, i.e. $PCP_LOG_DIR/pmcd. If the log file cannot be cre‐
ated or is not writable, output is written to the standard error
instead.
-s Amount of time (in seconds) between subsequent evaluations of the
shell trace file descriptor(s). The default is 2 seconds.
-m Maximum amount of memory to be allowed for each event queue (one
per traced process). The default is 2 megabytes.
INSTALLATION
In order for a host to export the names, help text and values for the
bash performance metrics, do the following as root:
# cd $PCP_PMDAS_DIR/bash
# ./Install
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.
If you want to undo the installation, do the following as root:
# cd $PCP_PMDAS_DIR/bash
# ./Remove
pmdabash is launched by pmcd(1) and should never be executed directly.
The Install and Remove scripts notify pmcd(1) when the agent is
installed or removed.
INSTRUMENTATION
In order to allow the flow of event data between a bash(1) script and
pmdabash, the script should take the following actions:
#!/bin/sh
source $PCP_DIR/etc/pcp.sh
pcp_trace on $@ # enable tracing
echo "awoke, $count"
pcp_trace off # disable tracing
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:
$ 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
When an instrumented script is running, the generation of event records
can be verified using the pmevent(1) command, as follows:
$ 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"
FILES
$PCP_PMCDCONF_PATH
command line options used to launch pmdabash
$PCP_PMDAS_DIR/bash/help
default help text file for the bash metrics
$PCP_PMDAS_DIR/bash/Install
installation script for the pmdabash agent
$PCP_PMDAS_DIR/bash/Remove
undo installation script for pmdabash
$PCP_LOG_DIR/pmcd/bash.log
default log file for error messages and other information
from pmdabashPCP ENVIRONMENT
Environment variables with the prefix PCP_ are used to parameterise 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 ALSObash(1), pmevent(1) and pmcd(1).
Performance Co-Pilot PCP PMDABASH(1)
