Cluster health API in Elasticsearch - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the Cluster Health API in Elasticsearch?

The Cluster Health API provides information about the health status of an Elasticsearch cluster, including the status of nodes, shards, and indices to help monitor cluster stability and performance.

beginner

What are the possible health status values returned by the Cluster Health API?

The health status can be green (all primary and replica shards are active), yellow (all primary shards are active but some replicas are not), or red (some primary shards are not active).

beginner

How do you request the cluster health status using the Elasticsearch REST API?

You send a GET request to /_cluster/health. For example: GET /_cluster/health returns the overall cluster health.

intermediate

What does the wait_for_status parameter do in the Cluster Health API?

It makes the API call wait until the cluster reaches the specified health status (green, yellow, or red) or until a timeout occurs, useful for monitoring or automation.

intermediate

What key information does the Cluster Health API response include?

The response includes cluster name, status, number of nodes, number of data nodes, active primary shards, active shards, relocating shards, initializing shards, unassigned shards, and timed_out flag.

Which HTTP method is used to check cluster health in Elasticsearch?

A DELETE

B GET

C PUT

D POST

The Cluster Health API uses the GET method to retrieve health information.

What does a 'yellow' status mean in cluster health?

A All primary shards are active but some replicas are not

B Some primary shards are not active

C All primary and replica shards are active

D Cluster is offline

Yellow means all primary shards are active but some replica shards are not.

Which parameter makes the Cluster Health API wait for a specific status?

A wait_for_nodes

B level

C timeout

D wait_for_status

The 'wait_for_status' parameter waits until the cluster reaches the specified health status.

What does the 'timed_out' field in the response indicate?

A The API call timed out before reaching the desired status

B The cluster is down

C The cluster is healthy

D The API call was successful

The 'timed_out' field shows if the API call timed out waiting for the cluster to reach the requested status.

Which endpoint is used to get health information for a specific index?

A /_cluster/health

B /index_name/_health

C /_cluster/health/index_name

D /_health/index_name

You append the index name to the cluster health endpoint to get health info for that index.

Explain how the Cluster Health API helps monitor an Elasticsearch cluster.

Think about what information you get and how it shows cluster stability.

Describe the meaning of green, yellow, and red statuses in the Cluster Health API.

Relate the colors to shard availability.