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This page discusses the usage of PPSS on a single host. Examples show how PPSS is used.
= Overview of modes and options =
The following output is displayed by PPSS when executed without any options:
{{{
istributed Parallel Processing Shell Script
Version: 2.0
PPSS is a Bash shell script that executes commands in parallel on a set
of items, such as files, or lines in a file.
Usage: ./ppss.sh MODE [ options ]
or
Usage: ./ppss.sh MODE -c <config file>
Modes are:
standalone For execution of PPSS on a single host.
node For execution of PPSS on a node, that is part of a 'cluster'.
config Generate a config file based on the supplied option parameters.
deploy Deploy PPSS and related files on the specified nodes.
erase Erase PPSS and related files from the specified nodes.
start Starting PPSS on nodes.
pause Pausing PPSS on all nodes.
stop Stopping PPSS on all nodes.
Options are:
--command | -c Command to execute. Syntax: '<command> ' including the single quotes.
Example: -c 'ls -alh '. It is also possible to specify where an item
must be inserted: 'cp "$ITEM" /somedir'.
--sourcedir | -d Directory that contains files that must be processed. Individual files
are fed as an argument to the command that has been specified with -c.
--sourcefile | -f Each single line of the supplied file will be fed as an item to the
command that has been specified with -c.
--config | -c If the mode is config, a config file with the specified name will be
generated based on all the options specified. In the other modes.
this option will result in PPSS reading the config file and start
processing items based on the settings of this file.
--enable-ht | -j Enable hyperthreading. Is disabled by default.
--log | -l Sets the name of the log file. The default is ppss-log.txt.
--processes | -p Start the specified number of processes. Ignore the number of available
CPU's.
The following options are used for distributed execution of PPSS.
--server | -s Specifies the SSH server that is used for communication between nodes.
Using SSH, file locks are created, informing other nodes that an item
is locked. Also, often items, such as files, reside on this host. SCP
is used to transfer files from this host to nodes for local procesing.
--node | -n File containig a list of nodes that act as PPSS clients. One IP / DNS
name per line.
--key | -k The SSH key that a node uses to connect to the server.
--user | -u The SSH user name that is used when logging in into the master SSH
server.
--script | -s Specifies the script/program that must be copied to the nodes for
execution through PPSS. Only used in the deploy mode.
This option should be specified if necessary when generating a config.
--transfer | -t This option specifies that an item will be downloaded by the node
from the server or share to the local node for processing.
--no-scp | -b Do not use scp for downloading items. Use cp instead. Assumes that a
network file system (NFS/SMB) is mounted under a local mountpoint.
--outputdir | -o Directory on server where processed files are put. If the result of
encoding a wav file is an mp3 file, the mp3 file is put in the
directory specified with this option.
Example: encoding some wav files to mp3 using lame:
./ppss.sh standalone -c 'lame ' -d /path/to/wavfiles -j
Running PPSS based on a configuration file.
./ppss.sh node -C config.cfg
Running PPSS on a client as part of a cluster.
./ppss.sh node -d /somedir -c 'cp /some/destination' -s 10.0.0.50 -u ppss -t -k ppss-key.key
}}
A detailed explanation based on examples will follow.
= How to use PPSS =
PPSS allows a user to execute commands, scripts or programs in parallel. That's it. It's sole purpose is to turn a batch job into a parallel batch job. This is relevant, since modern day processors are almost always multi-core and are designed to process jobs in parallel, so why not use it?
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If you tailor your command the right way, or create a (small) script, it is very easy to determine which items have not been processed correctly. A simple grep on 'error' might already give a clue.
*Important:* If a log file exists for an item, within the job_log directory, and PPSS is run again, that item will be skipped. This allows you to interrupt PPSS and continue where you left off. If you want to process all items again, just remove the job_log directory.
*Important:* If a log file exists for an item, within the job_log directory, and PPSS is run again, that item will be skipped. This allows you to interrupt PPSS and continue where you left off. If you want to process all items again, just remove the job_log directory.