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Execution

What is executed upon a Moa run can either be defined by a plugin, or by a template. Most Moa commands (such as moa show are plugin defined). Only moa prepare, moa run and moa finish call code defined in a template.

Each Moa run goes through a number of processes during execution:

  • Main invocation
  • hook prepare_background
  • Step 1 - Background check
  • hook: post_background or background_exit
  • Step 2 - Recursive check
  • Step 3 - Execute

Main invocation

The complete Moa Invocation is embedded in a try / except.

On an error, Moa tries to executed a post_error hook and only then further raise the error

Upon keyboard interrupt, Moa executes the post_interrupt hook and exists with a return code of -2.

Step 1 - Background check

Is '--bg' defined on the command line? If so, fork, let the child thread continue and let parent thread exit.

Before continuation, the parent thread executes the background_exit hook. The child thread executes the post_background hook.

Step 2 - Recursive check

Moa can be executed recursively by defining -r on the command line. If -r is defined on the commandline, Moa will check what recursivity mode the command has, and proceed accordingly. If it concerns a template defined command - the recusivity mode is always global, plugins have more options.

global recursive mode (default)
Recursive operation is executed at the top level. This means that Moa starts walking through the directory structure (starting at cwd) and executes the command in each directory subsequently (proceeding with step 3). The approach is depth first. Directories are processed alphabetically and directories starting with '.' or '_' are ignored. This is the only option for template defined commands.
local recursive mode
Only for plugins - Recursive operation is executed by the plugin. From the top level this means that Moa proceeds as if -r has not been defined and expects the plugin callback to deal with recursivity.
none recursive mode
Only for plugins - recusive execution is not allowed - Moa should exit with an error message

Each Moa template can have three that are executed in successively:

  • Prepare
  • Run
  • Finish