Exploring an Elasticsearch-Cluster

Our service Jobpushy is heavily based on the great Elasticsearch product. We want to give something back. Therefore we would publish some good stuff about Elasticsearch from time to time. Today we start with the most usable commands for exploring (an existing) cluster.
If you have the task to examine an Elasticseach installation, the following commands are the ones you need to use most of the time:

Command	Description
Versions and Cluster/Node-Names GET /	The first thing you need to do. Check what kind of Elasticsearch is running your cluster!
Cluster Health GET /_cat/health?v	Is your cluster running smoothly? Are all nodes and (replica-)shards running? Check if status==green! ES-doc
Cluster Statistics & Count GET /_cluster/stats?human	Get detailed statistics all in one: Doc-Count, Shard-Count, Size/Storage, Nodes, Operation System, free Memory, Java-Versions, Plugins ..... ES-doc
Indices - Status & Size GET /_cat/indices?v&s=store.size:desc	List all indices sorted by size. Shows their status. Particularly if the health status above is yellow you can break down which index isn't green. (Common case for a yellow-status: You have just one node but replicas defined for a specific index). Shows also doc-count and index-size! ES-doc
Shards - Check status / replication GET /_cat/shards?v	List all shards and shows the status. Useful if your cluster is in health status yellow or red. You can check which shards are running, which are replicated and which index has missing shards. ES-doc
Aliases Overview GET /_cat/aliases?v	Are there any aliases defined which should be used to access an index? Do the aliases include filters or routing-configuration? ES-doc
Nodes Overview GET /_cat/nodes?v	If you are running Elasticsearch with more than one instance (server) you can list all your nodes with this command. ES-doc
Plugins for each Node GET /_cat/plugins?v	Check if there are any plugins installed. If so, do they run on all nodes? ES-doc
Index Templates GET /_cat/templates?v GET _template/<template-name>	Are there any Index-Templates defined? Second command shows the specific settings and mapping-configs of a template (or all with *) that gets applied at index creation time. ES-doc
Settings GET /<index-pattern>/_settings/	Shows the settings of a specific index (including analysis-stuff, names, shard-configuration and more....). ES-doc
Types & Mappings GET /<index-pattern>/_mapping/<?type>	Shows the mapping-configuration for all types of a specific index. Optional you can specify a type for restricting mapping-information. (Tip: If you just wanna view types and if you use Kibana use GET /<index>/_mapping/, click in the result window, press Ctrl-Alt-0 and expand....) ES-doc
Doc-Count per Type GET /<index-pattern>/_search { "size": 0, "aggs": { "countType": { "terms": { "field": "_type" } } } }	Counts the available documents for each document-type. (Note: Types without any docs are not found and therefore not shown in the result.) ES-doc
Search some documents GET /<index-pattern>/<?type>/_search?size=3&_source=<field-name>,<field-name>&q=<field-name>:<searchterm>	Show some (random) documents. Good to see some example docs or search for a specific one. Use "size" and "_source" to restrict output. Use parameter "q" to search for something specific. (<?type>/-path and any parameter can be omitted!) ES-doc
Get document GET /<index-name>/_all/<doc-id>	If you need a concrete document and you know the index-name and the doc-id ("_id") this is the fasted way to go. ES-doc
Analyzing indexed text GET /<index_name>/_analyze { "analyzer":"<analyzer-name>", "text":"<your text>" }	Check how text-analyzing works for your index. First check for analyzer-names with the _settings command above. Use "standard" as analyzer-name if you would like to test with the Elasticsearch standard-analyzer. Remove the "analyzer"-parameter to check the "default"-analyzer behavior. <your text> is analyzed and you see the resulting tokens (used for indexing and search-queries). ES-doc
Validate & explain query GET <index_name>/_all/_validate/query?rewrite=true&explain=true { "query": { <your-query> } }	Get insides into your query. Using the "rewrite" parameter the actual Lucene query that will be executed is shown. The "explain" parameter gives you more detailed information about why a query failed. ES-doc

All commands above can be found on a text-only page, that can be used to execute the commands with Curl or a REST-Client like the Kibana-Console:
Page with all commands for easy copy&paste
Alternative you can open the commands above directly in your Kibana-Console. Click: