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:
The replicator service is starting up and reading the replicator properties configuration file.
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.
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.
The replicator is currently reading provisioning information from
the Source database before entering the
ONLINE state.
The replicator is preparing to go online and is currently restoring data from a backup.
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 an Applier has been switched online after maintenance, or in the event of a temporary network error where the Applier has reconnected to the Extractor.
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.
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.
This status will be seen on an Extractor replicator and is indicative of the replicator loosing connectivity to
the Source Database that it is extracting from. The replicator will still continue to extract entries from
the binary log that have not yet been processed. After extracting all log entries, the replicator will
proceed to the ONLINE:DEGRADED-BINLOG-FULLY-READ state.
ONLINE:DEGRADED-BINLOG-FULLY-READ
This status will be seen on an Extractor replicator following the
ONLINE:DEGRADED state
and indicates that the replicator has completed reading all binglog entries. In a clustering
environment, it indicates to the cluster that failover can now proceed.
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.