Service resources triggers¶

Introduction¶

Triggers are scripts or commands executed before or after a resource action.

Syntax¶

In a service resource configuration section, triggers can be defined using a keyword formatted as

[blocking_]<when>_<action>[@<scope>] = <command>

Blocking¶

If the blocking_ prefix is set, a non-zero command return code causes the service action to abort on error.

If the blocking_ prefix is not set, a non-zero command return code causes an error log, but the service action continues.

When¶

Supported values:

pre The command is executed before the normal resource driver action.
post The command is executed after the normal resource driver action.

Action¶

Supported values:

start
stop
run
provision
unprovision
sync_nodes
sync_drp
sync_resync
sync_update

Command¶

The command value supports shell expressions, like &&, ||, ...

Warning

; is interpreted as a comment begin marker if preceded by a whitespace. To use this character as a separator between commands, be sure to not insert a whitespace before. Example: post_start = echo hey; echo ya is valid but post_start = echo hey ; echo ya is not.

Use cases¶

Inter-service dependencies

Using a pre_start trigger to implement a wait loop for a tiers service expected state. A blocking_pre_start trigger can be combined with a wait loop timeout to abort the service startup if the required tiers service does not reach the expected state in time.
Service provisioning

Using a post_provision trigger to create directories, files, run configuration management, deploy app, ... just after the filesystems are provisioned and started.
Extra start checks

Using a blocking_pre_start on the first started resource to verify extra conditions to allow service instance startup.