Cluster health API in Elasticsearch - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this cluster health API call?

Given the following Elasticsearch cluster health API request, what is the value of the status field in the response?

Elasticsearch

GET /_cluster/health

Response example:
{
  "cluster_name": "my_cluster",
  "status": "green",
  "timed_out": false,
  "number_of_nodes": 3,
  "number_of_data_nodes": 2,
  "active_primary_shards": 10,
  "active_shards": 20,
  "relocating_shards": 0,
  "initializing_shards": 0,
  "unassigned_shards": 0
}

A "blue"

B "yellow"

C "red"

D "green"

💡 Hint

Look at the status field in the JSON response.

The status field in the cluster health API response indicates the health of the cluster. Here, it is "green", meaning all primary and replica shards are allocated.

🧠 Conceptual

intermediate

What does the unassigned_shards field indicate in cluster health?

In the Elasticsearch cluster health API response, what does the unassigned_shards field represent?

A The number of nodes that are down

B The number of shards that are not allocated to any node

C The total number of shards in the cluster

D The number of shards currently relocating between nodes

💡 Hint

Think about shards that are missing or waiting to be assigned.

The unassigned_shards field shows how many shards are not currently allocated to any node, which can indicate problems in the cluster.

❓ Predict Output

advanced

What is the output of this filtered cluster health API call?

Given this request to get cluster health only for the index logs-2023, what will be the value of active_shards in the response?

Elasticsearch

GET /_cluster/health/logs-2023

Response example:
{
  "cluster_name": "my_cluster",
  "status": "yellow",
  "timed_out": false,
  "number_of_nodes": 3,
  "number_of_data_nodes": 2,
  "active_primary_shards": 5,
  "active_shards": 7,
  "relocating_shards": 1,
  "initializing_shards": 0,
  "unassigned_shards": 2
}

A 7

B 5

C 2

D 0

💡 Hint

Check the active_shards field in the response.

The active_shards field shows the total number of shards (primary and replica) that are active for the specified index.

❓ Predict Output

advanced

What error does this invalid cluster health API request produce?

What error will this request produce? GET /_cluster/health?level=invalid_level

Elasticsearch

GET /_cluster/health?level=invalid_level

A 404 Not Found error

B 200 OK with default cluster health response

C 400 Bad Request with error about invalid level parameter

D 500 Internal Server Error

💡 Hint

The level parameter accepts only specific values like cluster, indices, or shards.

Using an invalid value for the level parameter causes Elasticsearch to return a 400 Bad Request error explaining the invalid parameter.

🧠 Conceptual

expert

How does the cluster health API determine the overall cluster status?

Which of the following best describes how Elasticsearch determines the overall status field in the cluster health API response?

A It is green if all primary and replica shards are allocated, yellow if all primary shards are allocated but some replicas are unassigned, and red if any primary shard is unassigned

B It is green if all nodes are up, yellow if any node is down, and red if the master node is down

C It is green if the cluster has no unassigned shards, yellow if there are relocating shards, and red if there are initializing shards

D It is green if the cluster has less than 5 nodes, yellow if between 5 and 10 nodes, and red if more than 10 nodes

💡 Hint

Think about shard allocation and its impact on cluster health colors.

The cluster health status is green when all primary and replica shards are allocated, yellow when all primary shards are allocated but some replicas are missing, and red when any primary shard is unassigned.