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Manage Oplog Storage

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Throughout the lifecycle of a backup, MongoDB Agent with Backup enabled tails the oplog of each replica set and sends new oplog entries to Ops Manager. The Agent sends the oplog entries in compressed bundles of approximately 10 MB in size called oplog slices. These oplog slices are stored in one or more MongoDB databases called oplog stores. Every Ops Manager deployment needs at least one oplog store.

When you enable backups, Ops Manager prompts you to create your first oplog store. This can be a local oplog store or an S3 oplog store. Once you create the first oplog store, you manage it separately from your snapshot stores. You can create additional oplog stores.

This tutorial covers creating additional Oplog Stores to store oplog entries. Like any MongoDB instance, Oplog Stores can exist on any host running MongoDB that the Ops Manager application can access.

Prerequisites

Before creating any Oplog Stores:

Procedures

The format of the Username and Password depend upon the authentication mechanism. Select one of the following tabs:

Add One Oplog Store

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2

Click Create New Oplog Store.

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Provide the Oplog Store details.

Field Necessity Action
Name Required Type the label for the Oplog Store.
Datastore Type Required Select Standalone, Replica Set or Sharded Cluster.
MongoDB Host List Conditional

Type a comma-separated list of mongod instances (for a Replica Set) or mongos instances (for a Sharded Cluster) in the <hostname:port> format that comprise the Oplog Store database.

Example

host1.example.com:27017, host2.example.com:27017, host2.example.com:27018

This field displays only if you set Datastore Type to Replica Set or Sharded Cluster.

MongoDB Hostname Conditional

Type the hostname of the standalone MongoDB instance.

This field displays only if you set Datastore Type to Standalone.

MongoDB Port Conditional

Type the port number of the standalone MongoDB instance.

This field displays only if you set Datastore Type to Standalone.

Username Optional

If you set this value:

Type the name of the user authorized to access the this database.

See also

SCRAM

Type the RFC 2253-formatted subject from the client certificate of the user authorized to access this database.

See also

x.509

Type the UPN of the user authorized to access this database.

See also

Kerberos

Type the name of the LDAP user authorized to access this database.

See also

LDAP

Password Optional

If you set this value:

Type the password associated with the username that can access this database.

See also

SCRAM

Leave it blank.

See also

x.509

Kerberos retrieves the password from its keytab file. Don’t type a password into this field.

See also

Kerberos

Type the password of the LDAP user authorized to access this database.

See also

LDAP

Warning

If you did not use the credentialstool to encrypt this password, it is stored as plaintext in the database.

Connection Options Optional

Type any additional connection string options for the MongoDB instance. This field supports unescaped values only.

For proper syntax, see Connection String URI Format in the MongoDB manual.

Encrypted Credentials Optional Select if the credentials for the database were encrypted using the credentialstool. The credentials include the Username, Password, AWS Access Key ID and AWS Secret Key.
Use TLS/SSL Optional

Select if the Oplog Store database only accepts connection encrypted using TLS.

Beyond this checkbox, to connect this oplog store using TLS, you must enable TLS on the oplog store database.

New Assignment Enabled Optional Select if you want to enable this Oplog Store after creating it. This is selected by default so the Oplog Store can be assigned backup jobs. If you clear this checkbox, the Oplog Store is created but you cannot assign backups to this Oplog Store.
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Click Create.

Edit One Existing Oplog Store

Ops Manager lists Oplog Stores in a table on the Oplog Storage page. Each row contains the settings for each local and S3 oplog store.

1

Navigate to the Oplog Storage page.

  1. Click the Admin link.
  2. Click the Backup tab.
  3. (Optional) If you have not previously set the head directory, set it in the Head Directory box.
  4. Click the Oplog Storage page.
2

Go to the row for the Oplog Store you want to edit.

3

Update any values that need to be changed.

In the MongoDB Connection column, update any values that need to be changed in the following fields:

Field Action
<hostname>:<port>

Type in one or more hosts that comprise the Oplog Store database in the <hostname:port> format.

Important

If these hosts are changed, the Oplog Store database they host must have the same data as the original Oplog Store database. Changing the host to a new Oplog Store database results in data loss.

  • If the Oplog Store database is a Replica Set or Sharded Cluster, type a comma-separated list of mongod instances (for a Replica Set) or mongos instances (for a Sharded Cluster).

    Example

    host1.example.com:27017, host2.example.com:27017, host2.example.com:27018

  • If the Oplog Store database is a standalone MongoDB instance, type the hostname:port of the instance.

MongoDB Auth Username

If you set this value:

Type the name of the user authorized to access the this database.

See also

SCRAM

Type the RFC 2253-formatted subject from the client certificate of the user authorized to access this database.

See also

x.509

Type the UPN of the user authorized to access this database.

See also

Kerberos

Type the name of the LDAP user authorized to access this database.

See also

LDAP

MongoDB Auth Password

If you set this value:

Type the password associated with the username that can access this database.

See also

SCRAM

Leave it blank.

See also

x.509

Kerberos retrieves the password from its keytab file. Don’t type a password into this field.

See also

Kerberos

Type the password of the LDAP user authorized to access this database.

See also

LDAP

Warning

If you did not use the credentialstool to encrypt this password, it is stored as plaintext in the database.

Note

Ops Manager doesn’t display the existing MongoDB Auth Password.

Encrypted Credentials Select if the credentials for the database were encrypted using the credentialstool. The credentials include the Username, Password, AWS Access Key ID and AWS Secret Key.
Use TLS/SSL

Select if the Oplog Store database only accepts connection encrypted using TLS.

Beyond this checkbox, to connect this oplog store using TLS, you must enable TLS on the oplog store database.

Connection Options Type any additional connection string options for the MongoDB instance. This field supports unescaped values only.
Assignment Labels Type a comma-separated list of labels to assign the Oplog Stores to specific projects.
Write Concern

Select your preferred Write Concern:

Default
Deployment Type Default Write Concern
Standalone Journaled
Replica sets or sharded clusters W2
Journaled A primary or standalone MongoDB instance acknowledged the write and wrote that write to their on-disk journals.
Acknowledged A primary or standalone acknowledged the write.
W2 More than one of the cluster members acknowledged the write.
Majority A majority of the replica set members acknowledged the write.
4

Select the checkbox in the Assignment Enabled column.

Select if you want to enable this Oplog Store after creating it. This is selected by default so the Oplog Store can be assigned backup jobs. If you clear this checkbox, the Oplog Store is created but you cannot assign backups to this Oplog Store.

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Click Save.

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Optional: Restart Ops Manager instances if needed.

If you change any connection string values or the Write Concern, restart all the Ops Manager instances including those running Backup Daemons.

Warning

Modifying the connection string values or the Write Concern for an existing blockstore requires you to restart all Ops Manager components, including those only running the Backup Daemon to apply those changes. Connection parameters include:

  • <hostname>:<port>
  • MongoDB Auth Username
  • MongoDB Auth Password
  • Encrypted Credentials
  • Use TLS/SSL
  • Connection Options
  • Write Concern

If you change to another Oplog Store host, the data on the existing Oplog Store is not copied automatically to the other Oplog Store.

See also

For more details on the MongoDB connection string URI, see Connection String URI Format in the MongoDB Manual.

Delete One Oplog Store

1

Navigate to the Oplog Storage page.

  1. Click the Admin link.
  2. Click the Backup tab.
  3. (Optional) If you have not previously set the head directory, set it in the Head Directory box.
  4. Click the Oplog Storage page.
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