Support external batch-mode tools within Node.js.
Many command line tools, like ExifTool and GraphicsMagick, support running in a "batch mode" that accept a series of discrete commands provided through stdin and results through stdout. As these tools can be fairly large, spinning them up can be expensive (especially on Windows).
This module expedites these commands, or "Tasks," by managing a cluster of these "batch" processes and queue of pending tasks, feeding processes pending tasks when they are idle. Tasks are monitored for errors and have timeouts, which cause the host process to be recycled. Batch processes are also recycled after processing N tasks or running for N seconds, in an effort to minimize the impact of memory leaks.
As of version 4, retry logic for tasks is a separate concern from this module.
This package powers exiftool-vendored, whose source you can examine as an example consumer.
Depending on your yarn/npm preference:
$ yarn add batch-cluster # or $ npm install --save batch-cluster
The child process must use
stdout for control/response.
BatchCluster will ensure a given process is only given one task at a time.
Create a singleton instance of BatchCluster.
Note the constructor options takes a union type of
Implement the Parser class to parse results from your child process.
See src/test.ts for an example child process. Note that the script is designed to be flaky on order to test BatchCluster's retry and error handling code.