Replication best practices

This section covers the best practices for replication based on our observations in production environments.

Purging obsolete replicas

About this task

By default, the PingDirectory server retains replicas for every server that has been part of a given topology. Over time, this can lead to an accumulation of obsolete replicas in your topology, which can increase the complexity of replication and negatively impact reliability.

To purge these obsolete replicas by default, you can set the replication-purge-obsolete-replicas global configuration property to true.

If you set replication-purge-obsolete-replicas to true, you must make this change on all servers, including new servers as they are added. Failure to do so could cause replicated servers to communicate an inconsistent state across the topology. An inconsistent state can lead to a replication-missing-changes alert and a server lockdown because of the missing replication changes.

Steps

To set replication-purge-obsolete-replicas to true, run dsconfig set-global-configuration-prop, as in the following example:

Example:
```
bin/dsconfig set-global-configuration-prop \
    --set replication-purge-obsolete-replicas:true
```

About the `dsreplication` command-line utility

The following points involve some security practices that apply to replication. For specific questions, contact your authorized support provider.

Developing Scripts

The dsreplication utility maintains the history of executed dsreplication commands with the full command-line arguments in the logs/tools/dsreplication.history file. Use the recorded commands to develop scripts to set up and configure replication.

Scripts invoking the dsreplication utility in non-interactive mode check the return code from the dsreplication process. A non-zero return code indicates a failure.

To exclude output messages from the dsreplication utility, use the --quiet option to suppress them.

By default, the utility fails if one or more warnings are issued during the command execution. To suppress warnings, use the --ignoreWarnings option.

This option is required when using dsreplication with non-fully-qualified host names, such as localhost. Otherwise dsreplication fails. However, you should avoiding using this flag in production environments.

Concurrent Use

With the exception of using the dsreplication utility with the status subcommand, the dsreplication subcommands cannot execute concurrently. The command-line utility locks the replication topology at one or more servers to prevent accidental configuration changes caused by multiple dsreplication subcommands running at the same time. For best practices, avoid making concurrent configuration changes.

Status

Using the dsreplication utility with the status subcommand requires the Replication Servers to provide monitoring information. This can lead to a delay before the output of dsreplication status displays. By default, dsreplication displays the status for all replicated domains with the exception of the special domains of the schema and the server registry.

Select a particular base distinguished name (DN) for dsreplication status if multiple base DNs are configured for replication.

Avoid invoking dsreplication status too often, such as more than once every 15 seconds or from multiple locations at the same time. Some of the information displayed by dsreplication status is based on monitor information that does not refresh every time the monitor is queried.

Do not use the status subcommand for collecting performance metrics. It is best to use the Periodic Stats Logger plugin for replication-related information.

Topology Tasks

The dsreplication tool allows specifying more than one server in a topology to act as the host for other servers for the enable and initialize actions. Use the --topologyFilePath option to specify a file with a series of hosts and ports in the topology.

For example, when the hosts file is used for an enable or initialize action, the servers in the file are tried sequentially until the new server is successfully enabled or added. The rest of the servers in the file are ignored. This ensures that a host server is always available. This file generates with the manage-topology export command.

Replication subcommand logs

To preserve important troubleshooting and support information, PingDirectory Server logs dsreplication subcommand executions, grouped by name, in the logs/tools directory. By default, the server retains the output from the last 10 executions for each subcommand (such as status, enable, and initialize). You can use these logs to review or troubleshoot the execution of a specific subcommand within the retention window.

The retention policy for these logs is not configurable.

If a dsreplication subcommand returns a non-standard result code, such as in the event of an error, the server generates a special log file:

Published to the logs/tools directory
Named according to the result code and timestamp of the execution
Compressed and retained indefinitely

Check these logs first to more quickly and effectively determine a root cause.

These non-standard logs should be created by the server infrequently and contain valuable information for support technicians. Don’t delete these files unless necessary. When you run the collect-support-data tool, it generates a support package that includes all non-standard logs and the six most recent logs for each subcommand.

PingDirectory