System Overview

mongo-connector creates a pipeline from a MongoDB cluster to one or more target systems, such as Solr, ElasticSearch, or another MongoDB cluster. By tailing the MongoDB oplog, it replicates operations from MongoDB to these systems in real-time. It has been tested with Python 2.6, 2.7, 3.3, and 3.4. Detailed documentation is available on the wiki.

Getting Started

Installation

The easiest way to install mongo-connector is with pip:

pip install mongo-connector

You can also install the development version of mongo-connector manually:

git clone https://github.com/10gen-labs/mongo-connector.git
cd mongo-connector
python setup.py install

You may have to run python setup.py install with sudo, depending on where you're installing mongo-connector and what privileges you have.

Using mongo-connector

mongo-connector replicates operations from the MongoDB oplog, so a replica set must be running before startup. For development purposes, you may find it convenient to run a one-node replica set (note that this is not recommended for production):

mongod --replSet myDevReplSet

To initialize your server as a replica set, run the following command in the mongo shell:

rs.initiate()

Once the replica set is running, you may start mongo-connector. The simplest invocation resembles the following:

mongo-connector -m <mongodb server hostname>:<replica set port> \
                -t <replication endpoint URL, e.g. http://localhost:8983/solr> \
                -d <path to DocManager, e.g. doc_managers/solr_doc_manager.py>

mongo-connector has many other options besides those demonstrated above. To get a full listing with descriptions, try mongo-connector --help.

Usage With Solr

There is an example Solr schema called schema.xml, which provides several field definitions on which mongo-connector relies, including:

• _id, the default unique key for documents in MongoDB (this may be changed with the --unique-key option)
• ns, the namespace from which the document came
• _ts, the timestamp from the oplog entry that last modified the document

The sample XML schema is designed to work with the tests. For a more complete guide to adding fields, review the Solr documentation.

You may also want to jump to the mongo-connector Solr wiki for more detailed information on using mongo-connector with Solr.

Troubleshooting

Installation

Some users have experienced trouble installing mongo-connector, noting error messages like the following:

Processing elasticsearch-0.4.4.tar.gz
Running elasticsearch-0.4.4/setup.py -q bdist_egg --dist-dir /tmp/easy_install-gg9U5p/elasticsearch-0.4.4/egg-dist-tmp-vajGnd
error: /tmp/easy_install-gg9U5p/elasticsearch-0.4.4/README.rst: No such file or directory

The workaround for this is making sure you have a recent version of setuptools installed. Any version after 0.6.26 should do the trick:

pip install --upgrade setuptools

Running mongo-connector after a long time

If you see a message like this from mongo-connector:

ERROR - OplogManager: Last entry no longer in oplog cannot recover! ...

then mongo-connector may have fallen behind in the oplog, and discrepencies must now be resolved between the contents of the target system and those in MongoDB. If you're just playing around with mongo-connector, however, then you may have stopped mongo-connector, made a bunch of requests to MongoDB or perhaps started a new replica set, then restarted mongo-connector, which will also cause this issue. In the latter case, all you need to do is use a new --oplog-ts file or erase the old one.