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Health Reports

How to Get Reports

In general, there are two channels to retrieve the health reports:

ceph (CLI)

The ceph CLI command sends the health Monitor command for retrieving the health status of the cluster.

Manager module

A Manager module calls the mgr.get('health') method for the same report in the form of a JSON encoded string.

The following diagrams outline the involved parties and how they interact when the clients query for the reports:

Where are the Reports Generated

Monitor: Aggregator of Aggregators

Monitor aggregates health reports from multiple Paxos services:

• AuthMonitor

• HealthMonitor

• MDSMonitor

• MgrMonitor

• MgrStatMonitor

• MonmapMonitor

• OSDMonitor

When each of the Paxos services persist the pending changes in their own domain, health-related issues are identified and stored into monstore with the prefix health using the same transaction. For instance:

• OSDMonitor checks a pending osdmap for possible issues such as down OSDs and a missing scrub flag in a pool and then stores the encoded form of the health reports along with the new osdmap. These reports are later loaded and decoded, so they can be collected on demand.

• MDSMonitor persists the health metrics contained in the beacon sent by the MDS daemons and prepares health reports when storing the pending changes.

To add a new warning related to CephFS, for example, a good place to start is MDSMonitor::encode_pending(), where health reports are collected from the latest FSMap and the health metrics reported by MDS daemons.

It is noteworthy that MgrStatMonitor does not prepare health reports. It receives aggregated reports from the Manager and then persists them to monstore.

Manager: a Delegate Aggregator

Monitor establishes consensus information including osdmap, mdsmap and monmap which is critical for cluster functioning. Aggregated statistics of the cluster are crucial for the administrator to understand the status of the cluster but they are not critical for cluster functioning. For scalability reasons they are offloaded to Manager which collects and aggregates the metrics.

Manager receives and processes MPGStats messages from OSDs. Daemons also report metrics and status periodically to Manager using MMgrReport. An aggregated report is then sent periodically to the Monitor MgrStatMonitor service which persists the data to monstore.

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