Status parameters of Stream nodes

The Stream service enables asynchronous flow of data between processes in Pega Platform. The Stream service is a multi-node component that is based on Apache Kafka. Use the following reference information to better understand the status parameters of Stream nodes.

Node ID: The identification number of the node in the cluster.

Disk

Disk usage: The disk space used by the Stream service on this node.
Free disk space: The remaining disk space that is allocated to this node.

Partition

Total: The number of partitions created in the Stream service.
Under-replicated: The number of partitions that are not synchronized with the leader node. For example, under-replication can occur when a Stream node fails.
Note: When you notice under-replicated partitions, check the status of your Stream nodes and troubleshoot them.
Offline: The number of partitions that do not have a leader. Partitions without a leader can happen when all brokers hosting replicas for this partition are down or no synchronized replica can take leadership due to message count issues. When a partition is offline, the Stream service does not process messages for that partition.
Note: When you notice offline partitions, check the status of your Stream nodes and troubleshoot them.
Leaders: The number of leaders that handle all of the read and write requests across all partitions. A single partition can only have one leader. For more information, see the Apache Kafka documentation.

Incoming byte rate

This section displays the amount of incoming traffic processed by the Stream service over specified periods of time and the overall mean value.

Outgoing byte rate

This section displays the amount of outgoing traffic processed by the Stream service over specified periods of time and the overall mean value.

Incoming message rate

This section displays the number of incoming records over specified periods of time and the overall mean value.

Processors

Network processors idle time: The average fraction of time that the network processor is idle.
Request handler threads idle time: The average fraction of time that the request handler threads are idle.

Note: The idle time value can be between 0 and 1, where 0 means that the processor is 100% busy, and 1 means that the processor is 100% free.

When the idle time is lower than 0.3, meaning that the processor is 70% busy, a warning is displayed in the Stream tab of the Services landing page. Verify what is causing the high demand on the processor and consider adding additional Stream nodes. For more information, see Configuring the Stream service and Assigning node types to nodes for on-premises environments.

Metrics

Replication max lag: The amount of elapsed time the replica is allowed before it is considered to be out of synchronization. This can happen if the replica does not contact the leader for more messages.
Is controller: When the value is equal to 1, the node is the active controller in this cluster. There can be only one active controller in the cluster.

For more information about the node metrics, see the Apache Kafka documentation.