@mapbox/watchbot-progress

watchbot-progress a series of tracking tools available on reduce-enabled Watchbot stacks to track the progress of distributed map-reduce operations. See the included examples.md for some basic worker recipes.

Installation

npm install watchbot-progress

Using the CLI command

A CLI command is available to report progress to Watchbot, and is accessible by default on reduce-enabled Watchbot stacks.

$ watchbot-progress --help

  Tracks the progress of a distributed map-reduce operation

  USAGE: watchbot-progress <command> <job-id> [options]

  Environment variable $ProgressTable must be set as the ARN for the DynamoDB
  table that is used to track progress.

  COMMANDS:
    - status: check the status of a job
    - set-total: set the total number of parts in a job
    - set-metadata: set arbitrary metadata on the job record
    - complete-part: complete a single part
    - fail-job: mark a job as a failure

  OPTIONS:
    -t, --total     (for set-total) the total number of parts in a job
    -p, --part      (for complete-part) the part number to mark as complete
    -m, --metadata  (for set-metadata) the JSON metadata object to store
    -r, --reason    (for fail-job) a description of why the job failed

Note that by default, workers in reduce-enabled Watchbot stacks will have the $ProgressTable environment variable set automatically.

Creating a progress table

A JavaScript module is available to create a DynamoDB table. You will need to provide any CloudFormation permissions.

var table = require('watchbot-progress').table;

This function requires 2 parameters:

• name: DynamoDB table name
• throughout: Object that contains user specification for progress table read and write capacity units:

- throughput.readCapacityUnits: Approximate number of reads per second from progress table - throughput.writeCapacityUnits: Approximate number of writes per second to progress table

Reporting progress in JavaScript

A JavaScript module is also available as a mechanism for progress reporting.

var progress = require('watchbot-progress').progress;

• progress.setTotal(jobId, total, callback): Set the total number of parts for a particular map-reduce operation.
• progress.completePart(jobId, part, callback): Mark a single part as complete. The response will be a boolean

value indicating whether or not the operation is completed.

• progress.setMetadata(jobId, metadata, callback): Associate arbitrary metadata with a particular map-reduce

operation.

• progress.status(jobId, callback): Read the status of a particular map-reduce operation.
• progress.failJob(jobId, reason, callback): Mark an operation as a failure, providing a description of what went

wrong.