To monitor and troubleshoot Elasticsearch, you can use various curl commands to retrieve information about the cluster's status, settings, and potential issues. Here's a summary of some essential commands:

Node Information:

curl -X GET "elasticsearch:9200/_nodes?pretty"

Retrieve detailed information about all nodes in the cluster.

Index Listing:

curl -X GET "elasticsearch:9200/_cat/indices?v"

Display a list of all indexes in the cluster.

Cluster Settings:

curl -X GET "elasticsearch:9200/_cluster/settings?pretty"

View the cluster's configuration settings.

Task Information:

curl -X GET "elasticsearch:9200/_cat/tasks?v"

Display running cluster tasks.

Allocation Information:

curl -X GET "elasticsearch:9200/_cat/allocation?v"

Show shard allocation information for each node.

Elasticsearch Logs:

You can directly check Elasticsearch logs to obtain error messages, warnings, and other crucial information. If Elasticsearch is running in a Docker container, you can view the container's logs using the following command:

docker logs [container_id_or_name]

Elasticsearch Tools:

Elasticsearch provides tools like elasticsearch-node and elasticsearch-setup-passwords to collect diagnostic information and manage settings. These tools are available within the directory where Elasticsearch binaries are installed.

By using these methods, endpoints, and tools, you can efficiently monitor the state, configuration, and potential issues of your Elasticsearch cluster.

Remember that Elasticsearch's health and status information can be pivotal for maintaining a healthy and performant cluster.