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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.

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

Procedure

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

    # dsconf <supplier2_instance_name> replication enable --suffix "dc=example,dc=com" --role "supplier" --replica-id 1 --bind-dn "cn=replication manager,cn=config" --bind-passwd "password"
    Copy to Clipboard Toggle word wrap

    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 <supplier2_instance_name> 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
...
    Copy to Clipboard Toggle word wrap

    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.

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 <supplier1_instance_name> replication enable --suffix "dc=example,dc=com" --role "supplier" --replica-id 2 --bind-dn "cn=replication manager,cn=config" --bind-passwd "password"
    Copy to Clipboard Toggle word wrap

    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 <supplier1_instance_name> 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
    Copy to Clipboard Toggle word wrap

    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 <supplier1_instance_name> 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
...
    Copy to Clipboard Toggle word wrap

    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 <supplier1_instance_name> repl-agmt init-status --suffix "dc=example,dc=com" example-agreement-supplier1-to-supplier2
Agreement successfully initialized.
    Copy to Clipboard Toggle word wrap

  3. Display the replication status: 

    # dsconf <supplier1_instance_name> 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)
    Copy to Clipboard Toggle word wrap

    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 <supplier1_instance_name> config replace nsslapd-idletimeout=7200
    Copy to Clipboard Toggle word wrap

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

To prepare the new server supplier2.example.com as a supplier, use either of the following methods:

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

Do not initialize the existing supplier from the new server. Otherwise, the empty database from the new server overrides the database on the existing supplier.

Apply the following procedure on the existing supplier:

  • Create a replication agreement to the new server.
  • Initialize the new server.

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 to the existing instance: 

    # dsconf <supplier2_instance_name> 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 example-agreement-supplier2-to-supplier1
    Copy to Clipboard Toggle word wrap

  • Add the replication agreement to the new instance by using --init option: 

    # dsconf <supplier1_instance_name> 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
    Copy to Clipboard Toggle word wrap

Verification

  1. Display the agreement status: 

    # dsconf <supplier2_instance_name> repl-agmt init-status --suffix "dc=example,dc=com" example-agreement-supplier2-to-supplier1
Agreement successfully initialized.
    Copy to Clipboard Toggle word wrap

  2. Display the replication status: 

    # dsconf <supplier2_instance_name> 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
    Copy to Clipboard Toggle word wrap

    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 <supplier2_instance_name> config replace nsslapd-idletimeout=7200
    Copy to Clipboard Toggle word wrap

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

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