8.3.1. Understanding Replicator States

Each node within the cluster will have a specific state that indicates whether the node is up and running and servicing requests, or whether there is a fault or problem. Understanding these states will enable you to clearly identify the current operational status of your nodes and cluster as a whole.

A list of the possible states for the replicator includes:

  • START

    The replicator service is starting up and reading the replicator properties configuration file.

  • OFFLINE:NORMAL

    The node has been deliberately placed into the offline mode by an administrator. No replication events are processed, and reading or writing to the underlying database does not take place.

  • OFFLINE:ERROR

    The node has entered the offline state because of an error. No replication events are processed, and reading or writing to the underlying database does not take place.

  • GOING-ONLINE:PROVISIONING

    The replicator is currently reading provisioning information from the master database before entering the ONLINE state.

  • GOING-ONLINE:RESTORING

    The replicator is preparing to go online and is currently restoring data from a backup.

  • GOING-ONLINE:SYNCHRONIZING

    The replicator is preparing to go online and is currently preparing to process any outstanding events from the incoming event stream. This mode occurs when a slave has been switched online after maintenance, or in the event of a temporary network error where the slave has reconnected to the master.

  • ONLINE

    The node is currently online and processing events, reading incoming data and applying those changes to the database as required. In this mode the current status and position within the replication stream is recorded and can be monitored. Replication will continue until an error or administrative condition switches the node into the OFFLINE state.

  • GOING-OFFLINE

    The replicator is processing any outstanding events or transactions that were in progress when the node was switched offline. When these transactions are complete, and the resources in use (memory, network connections) have been closed down, the replicator will switch to the OFFLINE:NORMAL state. This state may also be seen in a node where auto-enable is disabled after a start or restart operation.

In general, the state of a node during operation will go through a natural progression within certain situations. In normal operation, assuming no failures or problems, and no management requested offline, a node will remain in the ONLINE state indefinitely.

Maintenance on Tungsten Replicator or the dataserver must be performed while in the OFFLINE state. In the OFFLINE state, write locks on the THL and other files are released, and reads or writes from the dataserver are stopped until the replicator is ONLINE again.