Watching the status of an Elasticsearch cluster
editWatching the status of an Elasticsearch cluster
editYou can easily configure a basic watch to monitor the health of your Elasticsearch cluster:
- Schedule the watch and define an input that gets the cluster health status.
- Add a condition that evaluates the health status to determine if action is required.
- Take action if the cluster is RED.
Schedule the watch and add an input
editA watch schedule controls how often a watch is triggered. The watch input gets the data that you want to evaluate.
The simplest way to define a schedule is to specify an interval. For example, the following schedule runs every 10 seconds:
Schedules are typically configured to run less frequently. This example sets the interval to 10 seconds to you can easily see the watches being triggered. Since this watch runs so frequently, don’t forget to delete the watch when you’re done experimenting. |
To get the status of your cluster, you can call the Elasticsearch cluster health API:
response = client.cluster.health( pretty: true ) puts response
GET _cluster/health?pretty
To load the health status into your watch, you simply add an HTTP input that calls the cluster health API:
PUT _watcher/watch/cluster_health_watch { "trigger" : { "schedule" : { "interval" : "10s" } }, "input" : { "http" : { "request" : { "host" : "localhost", "port" : 9200, "path" : "/_cluster/health" } } } }
If you’re using Security, then you’ll also need to supply some authentication credentials as part of the watch configuration:
PUT _watcher/watch/cluster_health_watch { "trigger" : { "schedule" : { "interval" : "10s" } }, "input" : { "http" : { "request" : { "host" : "localhost", "port" : 9200, "path" : "/_cluster/health", "auth": { "basic": { "username": "elastic", "password": "x-pack-test-password" } } } } } }
It would be a good idea to create a user with the minimum privileges required for use with such a watch configuration.
Depending on how your cluster is configured, there may be additional settings required before the watch can access your cluster such as keystores, truststores, or certificates. For more information, see Watcher settings.
If you check the watch history, you’ll see that the cluster status is recorded
as part of the watch_record
each time the watch executes.
For example, the following request retrieves the last ten watch records from the watch history:
response = client.search( index: '.watcher-history*', body: { sort: [ { "result.execution_time": 'desc' } ] } ) puts response
GET .watcher-history*/_search { "sort" : [ { "result.execution_time" : "desc" } ] }
Add a condition
editA condition evaluates the data you’ve loaded into the watch and determines if any action is required. Since you’ve defined an input that loads the cluster status into the watch, you can define a condition that checks that status.
For example, you could add a condition to check to see if the status is RED.
PUT _watcher/watch/cluster_health_watch { "trigger" : { "schedule" : { "interval" : "10s" } }, "input" : { "http" : { "request" : { "host" : "localhost", "port" : 9200, "path" : "/_cluster/health" } } }, "condition" : { "compare" : { "ctx.payload.status" : { "eq" : "red" } } } }
Schedules are typically configured to run less frequently. This example sets the interval to 10 seconds to you can easily see the watches being triggered. |
If you check the watch history, you’ll see that the condition result is recorded
as part of the watch_record
each time the watch executes.
To check to see if the condition was met, you can run the following query.
response = client.search( index: '.watcher-history*', pretty: true, body: { query: { match: { "result.condition.met": true } } } ) puts response
GET .watcher-history*/_search?pretty { "query" : { "match" : { "result.condition.met" : true } } }
Take action
editRecording watch_records
in the watch history is nice, but the real power of
Watcher is being able to do something in response to an alert. A watch’s
actions define what to do when the watch condition is true—you
can send emails, call third-party webhooks, or write documents to an
Elasticsearch index or log when the watch condition is met.
For example, you could add an action to index the cluster status information when the status is RED.
PUT _watcher/watch/cluster_health_watch { "trigger" : { "schedule" : { "interval" : "10s" } }, "input" : { "http" : { "request" : { "host" : "localhost", "port" : 9200, "path" : "/_cluster/health" } } }, "condition" : { "compare" : { "ctx.payload.status" : { "eq" : "red" } } }, "actions" : { "send_email" : { "email" : { "to" : "username@example.org", "subject" : "Cluster Status Warning", "body" : "Cluster status is RED" } } } }
For Watcher to send email, you must configure an email account in your
elasticsearch.yml
configuration file and restart Elasticsearch. To add an email
account, set the xpack.notification.email.account
property.
For example, the following snippet configures a single Gmail account named work
:
xpack.notification.email.account: work: profile: gmail email_defaults: from: <email> smtp: auth: true starttls.enable: true host: smtp.gmail.com port: 587 user: <username> password: <password>
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If you have advanced security options enabled for your email account, you need to take additional steps to send email from Watcher. For more information, see Configuring email accounts.
You can check the watch history or the status_index
to see that the action was
performed.
response = client.search( index: '.watcher-history*', pretty: true, body: { query: { match: { "result.condition.met": true } } } ) puts response
GET .watcher-history*/_search?pretty { "query" : { "match" : { "result.condition.met" : true } } }
Delete the watch
editSince the cluster_health_watch
is configured to run every 10 seconds, make
sure you delete it when you’re done experimenting. Otherwise, you’ll spam yourself
indefinitely.
To remove the watch, use the delete watch API:
response = client.watcher.delete_watch( id: 'cluster_health_watch' ) puts response
DELETE _watcher/watch/cluster_health_watch