(See Job Lifecycle for an explanation of when pre-start scripts run.)
This feature is available with bosh-release v206+ (1.3072.0) and only for releases deployed with 3125+ stemcells.
Releases that make use of pre-start scripts and are deployed on older stemcells or with an older Director may potentially deploy; however, pre-start script will not be called.
Release job can have a pre-start script that will run before the job is started. This script allows the job to prepare machine and/or persistent data before starting its operation. For example, when writing a release for Cassandra, each node will need to migrate format of SSTables. That procedure may be lengthy and should happen before the node can successfully start.
To add a pre-start script to a release job:
- Create a script with any name in the templates directory of a release job.
- In the
templatessection of the release job spec file, add the script name and the
bin/pre-startdirectory as a key value pair.
--- name: cassandra_node templates: pre-start.erb: bin/pre-start
Pre-start script is usually just a regular shell script. ERB tags may be used for templating. Since pre-start script is executed in a similar way as other release job scripts (start, stop, drain scripts) you can use job's package dependencies.
After templating, the pre-start script must have its shebang on the first line.
Pre-start script should be idempotent. It may be called multiple times before process is successfully started.
Unlike a drain script, a pre-start script uses an exit code to indicate its success (exit code 0) or failure (any other exit code).
Pre-start script is called every time before job is started (ctl script is called) by the Director, which means that pre-start script should perform its operations in an idempotent way.
monit start directly on a VM will not trigger pre-start scripts.
Pre-start scripts in a single deployment job (typically is composed of multiple release jobs) are executed in parallel.
You can find logs for each release job's pre-start script in the following locations:
- stdout in
- stderr in
Since pre-start script will be called multiple times, new output will be appended to the files above. Standard log rotation policy applies.