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Rotate Keys for Sharded Clusters

Sharded cluster members can use keyfiles to authenticate each other as memers of the same deployment.

Starting in version 4.2, a keyfile can contain multiple keys and membership authentication is established if at least one key is common across members. This allows for rolling upgrade of the keys without downtime.

The following tutorial steps through the process to update, without any downtime, the key for a sharded cluster. [1]

Warning

The example keys in this tutorial are for illustrative purposes only. Do NOT use for your deployement. Instead, generate a keyfile using any method you choose (e.g. openssl rand -base64 756, etc.).

Consider a sharded cluster where each member's keyfile contains the following key:

Image of current key to replace.

The following procedure updates the sharded cluster members to use a new key:

Image of new key.
[1] This tutorial is not applicable to the keyfile used for the MongoDB's encrypted storage engine local key management. That keyfile can only contain a single key.

Modify each member's keyfile to include both the old and new keys. You can specify multiple keys either as strings enclosed in quotes or as a sequence of keys.

Warning

The example keys in this tutorial are for illustrative purposes only. Do NOT use for your deployement. Instead, generate a keyfile using any method you choose (e.g. openssl rand -base64 756, etc.).

Once all the keyfiles contain both the old and new keys, restart each member one at a time.

For each secondary of the config server replica set (CSRS), connect a mongo shell to the member and:

  1. Use the db.shutdownServer() method to shut down the member:

    use admin
    db.shutdownServer()
  2. Restart the member.

For the primary, connect a mongo shell to the member and

  1. Use rs.stepDown() to step down the member:

    rs.stepDown()
  2. Use the db.shutdownServer() method to shut down the member:

    use admin
    db.shutdownServer()
  3. Restart the member.

For each secondary member of the shard replica sets, connect a mongo shell to the member and:

  1. Use the db.shutdownServer() method to shut down the member:

    use admin
    db.shutdownServer()
  2. Restart the member.

For the primary of each shard replica set, connect a mongo shell to the member and

  1. Use rs.stepDown() to step down the member:

    rs.stepDown()
  2. Use the db.shutdownServer() method to shut down the member:

    use admin
    db.shutdownServer()
  3. Restart the member.

For each mongos/router instance, connect a mongo shell to the mongos instance and:

  1. Use the db.shutdownServer() method to shut down the member:

    use admin
    db.shutdownServer()
  2. Restart the member.

Once all members have been restarted, the members now accept either the old or new key for membership authentication.

Warning

The example keys in this tutorial are for illustrative purposes only. Do NOT use for your deployement. Instead, generate a keyfile using any method you choose (e.g. openssl rand -base64 756, etc.).

Modify each member's keyfile to include only the new password.

Image of new key.

Once all the keyfiles contain the new key only, restart each member one at a time.

For each secondary of the config server replica set (CSRS), connect a mongo shell to the member and:

  1. Use the db.shutdownServer() method to shut down the member:

    use admin
    db.shutdownServer()
  2. Restart the member.

For the primary, connect a mongo shell to the member and

  1. Use rs.stepDown() to step down the member:

    rs.stepDown()
  2. Use the db.shutdownServer() method to shut down the member:

    use admin
    db.shutdownServer()
  3. Restart the member.

For each secondary member of the shard replica sets, connect a mongo shell to the member and:

  1. Use the db.shutdownServer() method to shut down the member:

    use admin
    db.shutdownServer()
  2. Restart the member.

For the primary of each shard replica set, connect a mongo shell to the member and

  1. Use rs.stepDown() to step down the member:

    rs.stepDown()
  2. Use the db.shutdownServer() method to shut down the member:

    use admin
    db.shutdownServer()
  3. Restart the member.

For each mongos/router instance, connect a mongo shell to the mongos instance and:

  1. Use the db.shutdownServer() method to shut down the member:

    use admin
    db.shutdownServer()
  2. Restart the member.

Once all members have been restarted, the members now accept only the new key for membership authentication.

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