@growit-io/google-cloud-storage-function v0.2.4

Google Cloud Storage Function

Background Function that handles object change events from a Cloud Storage bucket, and runs predefined actions for events matching a configurable set of rules.

Prerequisites

• Access to an existing Google Cloud project.
• A Cloud Storage bucket to monitor in your project.
• An idea of some actions you want to perform when events are emitted by the bucket.

Initial Setup

Check out the examples and copy one of them as a starting point for your own Cloud Function. Each example comes with complete setup instructions.

Basic Usage

/**
 * Background Cloud Function triggered by Cloud Storage events
 * @param {object} event The Cloud Storage event
 * @return {Promise}
 */
exports.monitor = require('@growit-io/google-cloud-storage-function')({
  // See Configuration, below
  loadConfigFromBucket: false,
  loadConfigFromSource: false,
  directories: {
    source: 'content',
    target: 'cache'
  },
  rules: [{
    events: ['add','update'],
    actions: ['copy']
  },{
    events: ['delete'],
    actions: ['deleteAll']
  }]
})

Configuration

The default configuration is in config.js. This default configuration will be merged at runtime with your own deployment configuration in config.json, the configuration supplied to the constructor of this Background Function, and with /config.json from the bucket, if it exists and loadConfigFromBucket is true.

Function

The top-level configuration options below affect the Background Function's mode of operation, and how it generates its runtime configuration.

Logging

The verbosity of the Background Function logs can be controlled with the logger.level option. Leave this at a reasonable low setting to avoid log spam if your bucket receives a lot of changes.

Directories

The Background Function will only evaluate rules for objects within directories.source, and modify objects only in directories.target. This restriction has a dual-purpose: to avoid event loops, and to encourage a distinction between original content and generated content in your bucket. If this is too restrictive for your scenario, set both options to "" to evaluate rules on all events, and to let actions modify objects anywhere in the bucket.

File Types

The only file type that has special significance is image; other file types may be defined to simplify your rules. The optiimise function in file.js detects whether a file is an image based on the configured image file type.

Example:

{
  "filetypes": {
    "image": {
      "match": "\\.(png|jpg|gif)$"
    },
    "json": {
      "match": "\\.json$"
    }
  }
}

Actions

Predefined actions can be referenced in the Rules section by name. By default, all exported functions in the file module are available to rules as actions. All other actions have to be defined in the configuration before they can be referenced in a rule.

Rules

Rules are evaluated sequentially for each change event emitted by the Cloud Storage bucket that relates to a file object within directories.source. Events for directories and file objects outside of the source directory are ignored. If a rule matches, then its actions are run in sequence and the rule evaluation stops, unless the rule has continue set to true.

Development

npm install --dev
mkdir -p content
npm run watch

Changelog

See CHANGELOG.md.

License

See the LICENSE file.