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Web UIs

Apache Ozone provides lightweight, read-only Web UIs for core services to support operational observability and troubleshooting. The primary service UIs are Storage Container Manager (SCM) and Ozone Manager (OM).

SCM Web UI​

SCM Web UI

The SCM Web UI exposes the runtime state and health of the storage layer managed by SCM. At a high level, it provides:

  • Service overview: SCM identity, version, JVM runtime, and cluster identifiers
  • Cluster summaries: Aggregate statistics for Datanode usage, capacity, pipelines, and containers
  • Datanode visibility: Per-node operational state, capacity usage, and heartbeat status
  • Safemode and HA status: Safemode rule evaluation and readiness information in HA deployments

The SCM Web UI also includes RPC metrics, showing operation counts, average latency, and success/failure statistics for SCM RPC calls.

OM Web UI​

OM Web UI

The Ozone Manager (OM) Web UI focuses on the metadata and namespace management layer. It provides:

  • Service overview: OM identity, namespace, version, JVM runtime, and startup information
  • HA and leadership status: Current role (leader/follower), election details, and group identifiers
  • Metadata storage information: Ratis log and RocksDB directory locations

In addition to standard RPC metrics, the OM Web UI exposes OM-specific metrics related to metadata operations and namespace activity, enabling operators to observe OM behavior beyond raw RPC performance.

Common Metrics and Diagnostic Servlets​

Both SCM and OM expose a common set of diagnostic endpoints and servlets:

  • RPC Metrics – Number of operations, average latency, and success/failure counts
  • JMX – JVM and service metrics via JMX
  • Config – Effective runtime configuration of the service
  • Stacks – Thread dump of the running process
  • Log Level – View and dynamically adjust logging levels

These endpoints are primarily intended for debugging, diagnostics, and integration with external monitoring systems.