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blue_colr, database-based process launcher¶ ↑
Overviewblue_colr allows you to easily launch processes using database as a queue. It consists of bluecolrd
, a deamon that executes whatever finds in a queue, and a DSL for enqueuing processes that enables you to easily describe the order and dependencies of processes.
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Installationgem install blue_colr
You may want to install log4r
gem as well, as it provides more powerful logging features than builtin Ruby’s Logger
.
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Examplerequire 'blue_colr' BlueColr.launch do run 'echo These processes' run 'echo will be ran sequentially.' parallel do run 'echo And these' sequential do run 'echo (but not' run 'echo these two)' end run 'echo in parallel.' end run 'echo These will execute' run 'echo after all above are finished.' end
Previous code will queue processes within the database, keeping them in dependency order. Those within sequential
block (and in root block, by default) will run each after the one before finishes. Those within parallel
block will run in parallel. The commands after parallel
block will be executed after all the commands in parallel
block are sucessfully finished.
Note: the code above will not start the processes by itself, but enqueue them to the database, by default. A separate process called bluecolrd
is used for that.
The following chart, generated by the same code above, is its execution sequence:
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Requirements and ConfigurationIn order to access the database, blue_colr requires sequel ORM library, if you don’t have it, its gem will be installed along with blue_colr.
Blue_colr uses a relational database to simulate a process queue so you will have to provide one. It relies on two tables, named process_items
and process_item_dependencies
to work. db/
directory contains Sequel migrations for creating these two:
sequel -m db/ sqlite://examples/test.db
Basic configuration is passed to blue_colr either by setting options from your code, or (if not set), blue_colr will parse your command line arguments and get the path to yaml configuration file, using -c
option.
bluecolrd
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Blue_colr daemon is constantly running, checking the database for newly enqueued processes, and executing them in a subshell, observing the order.
bcrun
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This script is used to launch arbitrary command through blue_colr. You might want to do that if you want to keep track of the stuff you launch (as everything goes through a database table).
bcrun -c path_to_config.yaml -x "command to execute"
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EnvironmentsAn environment is something like category which you assign to a set of processes when enqueuing them. Then you can have multiple daemons running, each one of them targeting specific environment. That allows easy distribution of your tasks across multiple machines, while keeping them synchronized, like the following scenario:
-
Start tasks
a
andb
on machineX
andc
on machineY
-
When all above are sucessfully done, start task
d
on machineZ
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ToDo-
More tests
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Better docs
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Examples