moplog

A generic processor of a MongoDB oplog, routing registered transactions to the specified consumer. It handles operations of type insert, update, delete, and command.

Usage

var Moplog = require ('moplog');
 
// Initialize with the location of the nconf config file to use and the 
// directory to the consumers.
var moplog = new Moplog('./config.json', './consumers');
 
// Assuming that your config has valid MongoDB connection details as well as
// valid consumers configured, this will kick off the processing.
moplog.connect();

Configuration

Configure moplog through a configuration file which you pass in as the first argument. Here is an example:

{
    "source": {
        "host": "mongodb://localhost:27017",
        "db": "local",
        "collection": "oplog.$main",
        "user": "",
        "pass": ""
    },
    "collections": {
        "myDatabase.myCollection": "myConsumer"
    }, 
    "period": 5000,
    "lastTs": 1429559350001
}

• source : MongoDB server with oplog to process
  • host : server hostname with mongodb:// prepended protocol (default: "mongodb://localhost:27017")
  • db : database name containing the oplog (default: "local")
  • collection : oplog collection name (default: "oplog.$main")
  • user : specify when server uses authentication, user must have access to oplog (default: "", i.e., no authentication)
  • pass : specify when server uses authentication, user must have access to oplog (default: "", i.e., no authentication)
• collections : map of database.collection to consumer to route operations to (default: {}, i.e., no consumers)
• period : how frequently to query for new oplog entries (defaults: 5000, i.e., 5 seconds)
• lastTs : timestamp of last processed oplog document with ms resolution. This is updated after each additional document is processed. (default: 0, i.e., from the earliest operation available)

New consumers should be added to the app/consumers subdirectory. Refer to test/consumers/testConsumer as a reference of how to implement.

API

Moplog(configFile, consumerDir)

Constructor which takes two arguments to specify the config file and the base directory of the consumers. Return a moplog instance.

Moplog.connect()

Connects to the MongoDB referenced in the config, obtains a handle on the oplog collection, and kicks off processing.

Moplog.getConfig()

Returns the active configuration. Example response:

{
  "source": {
    "host": "mongodb://localhost:27017",
    "db": "local",
    "collection": "oplog.$main",
    "user": "",
    "pass": ""
  },
  "collections": {
    "source.content": "defaultConsumer"
  },
  "period": 5000,
  "lastTs": 1430017964001
}

Moplog.getLag()

Returns the estimated lag in minutes of processed records based on timestamp of last processed operation. Example response:

{
  "lagInMinutes": 1230
}

Logging

Moplog logs to a rolling log stored in the process' root directory as moplog.dat. It also supports Loggly by setting the following environment variables:

• LOGGLY_SUBDOMAIN
• LOGGLY_AUTH
• LOGGLY_INPUT_NAME
• LOGGLY_INPUT_TOKEN

Testing

All linting are configured in Gruntfile.js using both jshint and jscs.

grunt lint

All mocha unit tests are included in the test/ directory. These are run through the test grunt task:

grunt unit

To determine unit test coverage, run the cov grunt task. A terminal friendly coverage output will give percentages and highlight lines not covered by any test:

grunt cov