A ServiceControl Error instance:
- Monitors the central
errorqueue and stores the failed messages making them available for manual retries using ServicePulse or ServiceInsight. - Aggregates and forwards data from Audit instances for visualization in ServiceInsight.
- Collects and serves heartbeat and custom check data for presentation by ServicePulse
- Publishes integration events that can be handled by user built endpoints that can perform a custom action when those events occur.
- If configured, forwards failed messages to an error log queue for custom processing.
Persistence
Each ServiceControl Error instance stores message data in a RavenDB database. For instances deployed using the ServiceControl Management Utility or PowerShell this database is embedded with the ServiceControl Error instance. For ServiceControl Error instances deployed using containers the database resides in a separate container.
Failed message data is retained until 7 days after successful retry is detected or the failed message is manually archived. This retention period can be customized.
The ServiceControl RavenDB server and databases are used exclusively by ServiceControl and are not intended for external manipulation or modifications.
Notifications
Health monitoring
ServiceControl includes some basic self-monitoring implemented as custom checks. These checks are reported in ServicePulse along with other custom checks.
MSMQ transactional dead letter queue
A machine running MSMQ has a single transactional dead letter queue. Messages that cannot be delivered to queues located on remote machines are eventually moved to the transactional dead letter queue. ServiceControl monitors the transactional dead letter queue on the machine it is installed on. The presence of messages in this queue may indicate problems delivering messages for retries.
Azure Service Bus staging dead letter queue
Every Azure Service Bus queue has an associated dead letter queue. When ServiceControl sends a message for retry, it uses a staging queue. ServiceControl monitors the dead letter queue associated with the staging queue. The presence of messages in the dead letter queue indicates problems delivering messages for retries.
Failed imports
When ServiceControl is unable to ingest an audit or error message, an error is logged and the message is stored separately. ServiceControl monitors these messages. For more information, see re-importing failed messages.
Error message ingestion process
When ServiceControl has difficulty connecting to the configured transport, the error message ingestion process is shut down for sixty seconds. These shutdowns are monitored. The time to wait before restarting the error ingestion process is controlled by the ServiceControl/TimeToRestartErrorIngestionAfterFailure setting.
Message database storage space
ServiceControl stores messages in an embedded database. If the drive containing the database runs out of storage space, message ingestion fails and the ServiceControl instance stops. This may cause instability in the database, even after storage space is increased. The remaining storage space on the drive is monitored. The check reports a failure if the drive has less than 20% remaining of its total capacity. This threshold is controlled by the ServiceControl/DataSpaceRemainingThreshold setting.
Critical message database storage space
This is similar to the Message database storage space check. However, in this case, if the drive containing the database has less than 5% remaining of its total capacity, message ingestion on the ServiceControl instance is stopped to prevent data loss, and a failure is reported. This threshold is controlled by the ServiceControl/MinimumStorageLeftRequiredForIngestion (for the error instance) and ServiceControl.Audit/MinimumStorageLeftRequiredForIngestion (for the audit instance) settings.