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Chapter 3. Configuring multi-supplier replication using the command line

In a multi-supplier replication environment, two or more writable suppliers replicate data with each other. For example, set up multi-supplier replication to provide a fail-over environment and distribute the load over multiple servers. Clients can then perform read and write operations on any host that is a read-write replica.

This section assumes that you have an existing Directory Server instance running on a host named supplier1.example.com. The procedures describe how to add another read-write replica named supplier2.example.com to the topology, and how to configure multi-supplier replication for the dc=example,dc=com suffix.

3.1. Preparing the new supplier using the command line

To prepare the supplier2.example.com host, enable replication. This process:

  • Configures the role of this server in the replication topology
  • Defines the suffix that is replicated
  • Creates the replication manager account the supplier uses to connect to this host

Perform this procedure on the supplier that you want to add to the replication topology.

Prerequisites

  • You installed the Directory Server instance.
  • The database for the dc=example,dc=com suffix exists.

Procedure

  • Enable replication for the dc=example,dc=com suffix:

    # dsconf -D "cn=Directory Manager" ldap://supplier2.example.com replication enable --suffix "dc=example,dc=com" --role "supplier" --replica-id 1 --bind-dn "cn=replication manager,cn=config" --bind-passwd "password"

    This command configures the supplier2.example.com host as a supplier for the dc=example,dc=com suffix, and sets the replica ID of this entry to 1. Additionally, the command creates the cn=replication manager,cn=config user with the specified password and allows this account to replicate changes for the suffix to this host.

    Important

    The replica ID must be a unique integer between 1 and 65534 for a suffix across all suppliers in the topology.

Verification

  • Display the replication configuration:

    # dsconf -D "cn=Directory Manager" ldap://supplier2.example.com replication get --suffix "dc=example,dc=com"
    dn: cn=replica,cn=dc\3Dexample\2Cdc\3Dcom,cn=mapping tree,cn=config
    ...
    nsDS5ReplicaBindDN: cn=replication manager,cn=config
    nsDS5ReplicaRoot: dc=example,dc=com
    nsDS5ReplicaType: 3
    ...

    These parameters indicate:

    • nsDS5ReplicaBindDN specifies the replication manager account.
    • nsDS5ReplicaRoot sets the suffix that is replicated.
    • nsDS5ReplicaType set to 3 defines that this host is a supplier.

3.2. Configuring the existing server as a supplier to the new server using the command line

To prepare the existing server supplier1.example.com as a supplier, you need to:

  • Enable replication for the suffix.
  • Create a replication agreement to the new supplier.
  • Initialize the new supplier.

Perform this procedure on the existing supplier in the replication topology.

Prerequisites

  • You enabled replication for the dc=example,dc=com suffix on the supplier to join.

Procedure

  1. Enable replication for the dc=example,dc=com suffix:

    # dsconf -D "cn=Directory Manager" ldap://supplier1.example.com replication enable --suffix "dc=example,dc=com" --role "supplier" --replica-id 2 --bind-dn "cn=replication manager,cn=config" --bind-passwd "password"

    This command configures the supplier1.example.com host as a supplier for the dc=example,dc=com suffix, and sets the replica ID of this entry to 2. Additionally, the command creates the cn=replication manager,cn=config user with the specified password and allows this account to replicate changes for the suffix to this host.

    Important

    The replica ID must be a unique integer between 1 and 65534 for a suffix across all suppliers in the topology.

  2. Add the replication agreement and initialize the new server:

    # dsconf -D "cn=Directory Manager" ldap://supplier1.example.com repl-agmt create --suffix "dc=example,dc=com" --host "supplier2.example.com" --port 389 --conn-protocol LDAP --bind-dn "cn=replication manager,cn=config" --bind-passwd "password" --bind-method SIMPLE --init example-agreement-supplier1-to-supplier2

    This command creates a replication agreement named example-agreement-supplier1-to-supplier2. The replication agreement defines settings, such as the new supplier’s host name, protocol, and authentication information that the supplier uses when connecting and replicating data to the new supplier.

    After the agreement was created, Directory Server initializes supplier2.example.com. Depending on the amount of data to replicate, initialization can be time-consuming.

Verification

  1. Display the replication configuration:

    # dsconf -D "cn=Directory Manager" ldap://supplier1.example.com replication get --suffix "dc=example,dc=com"
    dn: cn=replica,cn=dc\3Dexample\2Cdc\3Dcom,cn=mapping tree,cn=config
    ...
    nsDS5ReplicaBindDN: cn=replication manager,cn=config
    nsDS5ReplicaRoot: dc=example,dc=com
    nsDS5ReplicaType: 3
    ...

    These parameters indicate:

    • nsDS5ReplicaBindDN specifies the replication manager account.
    • nsDS5ReplicaRoot sets the suffix that is replicated.
    • nsDS5ReplicaType set to 3 defines that this host is a supplier.
  2. Verify whether the initialization was successful:

    # dsconf -D "cn=Directory Manager" ldap://supplier1.example.com repl-agmt init-status --suffix "dc=example,dc=com" example-agreement-supplier1-to-supplier2
    Agreement successfully initialized.
  3. Display the replication status:

    # dsconf -D "cn=Directory Manager" ldap://supplier1.example.com repl-agmt status --suffix "dc=example,dc=com" example-agreement-supplier1-to-supplier2
    Status For Agreement: "example-agreement-supplier1-to-supplier2" (supplier2.example.com:389)
    Replica Enabled: on
    Update In Progress: FALSE
    Last Update Start: 20210331071545Z
    Last Update End: 20210331071546Z
    Number Of Changes Sent: 2:1/0
    Number Of Changes Skipped: None
    Last Update Status: Error (0) Replica acquired successfully: Incremental update succeeded
    Last Init Start: 20210331071541Z
    Last Init End: 20210331071544Z
    Last Init Status: Error (0) Total update succeeded
    Reap Active: 0
    Replication Status: Not in Synchronization: supplier (6064219e000100020000) consumer (Unavailable) State (green) Reason (error (0) replica acquired successfully: incremental update succeeded)

    Verify the Replication Status and Last Update Status fields.

Troubleshooting

  1. By default, the replication idle timeout for all agreements on a server is 1 hour. If the initialization of large databases fails due to timeouts, set the nsslapd-idletimeout parameter to a higher value. For example, to set the parameter to 7200 (2 hours), enter:

    # dsconf -D "cn=Directory Manager" ldap://supplier1.example.com config replace nsslapd-idletimeout=7200

    To set an unlimited period, set nsslapd-idletimeout to 0.

3.3. Configuring the new server as a supplier to the existing server using the command line

To prepare the new server supplier2.example.com as a supplier, you need to:

  • Enable replication for the suffix.
  • Create a replication agreement to the existing server.
  • Initialize the existing server.

Perform this procedure on the existing supplier in the replication topology.

Warning

Do not continue if you have not initialized the replication agreement on the existing server. Otherwise, the empty database from the new server overrides the database on the existing supplier.

Prerequisites

  • You enabled replication for the dc=example,dc=com suffix on the new server.
  • You enabled replication for the dc=example,dc=com suffix on the existing server.
  • The new server to join is successfully initialized.

Procedure

  • Add the replication agreement and initialize the existing server:

    # dsconf -D "cn=Directory Manager" ldap://supplier2.example.com repl-agmt create --suffix "dc=example,dc=com" --host "supplier1.example.com" --port 389 --conn-protocol LDAP --bind-dn "cn=replication manager,cn=config" --bind-passwd "password" --bind-method SIMPLE --init example-agreement-supplier2-to-supplier1

Verification

  1. Verify whether the initialization was successful:

    # dsconf -D "cn=Directory Manager" ldap://supplier2.example.com repl-agmt init-status --suffix "dc=example,dc=com" example-agreement-supplier2-to-supplier1
    Agreement successfully initialized.
  2. Display the replication status:

    # dsconf -D "cn=Directory Manager" ldap://supplier2.example.com repl-agmt status --suffix "dc=example,dc=com" example-agreement-supplier2-to-supplier1
    Status For Agreement: ""example-agreement-supplier2-to-supplier1 (supplier1.example.com:389)
    Replica Enabled: on
    Update In Progress: FALSE
    Last Update Start: 20210331073540Z
    Last Update End: 20210331073540Z
    Number Of Changes Sent: 7:1/0
    Number Of Changes Skipped: None
    Last Update Status: Error (0) Replica acquired successfully: Incremental update succeeded
    Last Init Start: 20210331073535Z
    Last Init End: 20210331073539Z
    Last Init Status: Error (0) Total update succeeded
    Reap Active: 0
    Replication Status: Not in Synchronization: supplier (60642649000000070000) consumer (Unavailable) State (green) Reason (error (0) replica acquired successfully: incremental update succeeded)
    Replication Lag Time: Unavailable

    Verify the Replication Status and Last Update Status fields.

Troubleshooting

  1. By default, the replication idle timeout for all agreements on a server is 1 hour. If the initialization of large databases fails due to timeouts, set the nsslapd-idletimeout parameter to a higher value. For example, to set the parameter to 7200 (2 hours), enter:

    # dsconf -D "cn=Directory Manager" ldap://supplier2.example.com config replace nsslapd-idletimeout=7200

    To set an unlimited period, set nsslapd-idletimeout to 0.