Percona ClusterSync for MongoDB

Percona ClusterSync for MongoDB (PCSM) is a tool for cloning and replicating data between MongoDB clusters. It supports both replica sets and sharded clusters, handling initial data cloning followed by continuous change replication.

For more information about PCSM and how to use it, see Percona ClusterSync for MongoDB documentation.

Percona ClusterSync for MongoDB includes the following Features:

• Clone data from source to target MongoDB cluster
• Real-time change replication via MongoDB Change Streams
• Support for both replica sets and sharded clusters
• Namespace filtering (include/exclude databases and collections)
• Automatic index management on target cluster
• CLI tool as well as HTTP API

Installation

You can install Percona ClusterSync for MongoDB in the following ways:

• from Percona repository (recommended)
• build from source code

Find the installation instructions in the official documentation.

API

PCSM is a CLI tool, but also exposes HTTP API as well.

For reference see PCSM commands and HTTP API docs.

Target data write concern

Clone inserts and replication data writes default to majority. To change their acknowledgment requirement for a run, pass --target-write-concern=1 to pcsm start (or set PCSM_TARGET_WRITE_CONCERN=1 for it), or send {"targetWriteConcern":"1"} to /start. Values are majority or a positive integer. Unacknowledged writes (0) are not supported. The server has no write concern setting, so a run started without one uses majority. The value is stored with the run and retained during checkpoint recovery and HA takeover. Start a new run to change it. Checkpoints, HA state, and catalog DDL always use majority write concern.

Using 1 can reduce stalls when target secondaries lag, but acknowledgment from the primary alone does not make data majority-durable. A target primary failure can roll back acknowledged data, and a majority checkpoint does not guarantee that earlier data writes on other shards are durable. Keep majority when automatic recovery must preserve that guarantee. Lower it only for a controlled migration that can tolerate restarting and validating the copy after a target failure. Retain the source and verify target consistency before cutover.

Submit Bug Report / Feature Request

If you find a bug in Percona ClusterSync for MongoDB, submit a report to the project's JIRA issue tracker.

As a general rule of thumb, please try to create bug reports that are:

• Reproducible. Include steps to reproduce the problem.
• Specific. Include as much detail as possible: which version, what environment, etc.
• Unique. Do not duplicate existing tickets.
• Scoped to a Single Bug. One bug per report.

When submitting a bug report or a feature, please attach the following information:

• The output of the pcsm status command
• The output of the pcsm logs command

Licensing

Percona is dedicated to keeping open source open. Whenever possible, we strive to include permissive licensing for both our software and documentation. For this project, we are using the Apache License 2.0 license.

How to get involved

We encourage contributions and are always looking for new members who are as dedicated to serving the community as we are.

The Contributing Guide contains the guidelines for contributing.

Contact

You can reach us:

• on Percona ClusterSync for MongoDB Community Forum
• or Contact Form