Explain Lifecycle API

Request

The Explain Lifecycle API allows you to retrieve information about the execution of a Lifecycle Policy with respect to one or more indices.

ExplainLifecycleRequest request =
    new ExplainLifecycleRequest("my_index-1", "other_index"); 

Requests an explanation of policy execution for my_index and other_index

Response

The returned ExplainLifecycleResponse contains a map of LifecyclePolicyMetadata, accessible by the name of the policy, which contains data about each policy, as well as the policy definition.

Map<String, IndexLifecycleExplainResponse> indices =
    response.getIndexResponses();
IndexLifecycleExplainResponse myIndex = indices.get("my_index-1");
String policyName = myIndex.getPolicyName(); 
boolean isManaged = myIndex.managedByILM(); 

String phase = myIndex.getPhase(); 
long phaseTime = myIndex.getPhaseTime(); 
String action = myIndex.getAction(); 
long actionTime = myIndex.getActionTime();
String step = myIndex.getStep(); 
long stepTime = myIndex.getStepTime();

String failedStep = myIndex.getFailedStep(); 

The name of the policy in use for this index, if any. Will be null if the index does not have an associated policy.

Indicates whether this index is being managed by Index Lifecycle Management.

The Phase (hot, warm, etc.) this index is currently in. Will be null if the index is not managed by Index Lifecycle Management.

The time this index entered this Phase of execution.

The Action (rollover, shrink, etc.) this index is currently in. Will be null if the index is not managed by Index Lifecycle Management.

The Step this index is currently in. Will be null if the index is not managed by Index Lifecycle Management.

If this index is in the ERROR Step, this will indicate which Step failed. Otherwise, it will be null.

Synchronous Execution

When executing a ExplainLifecycleRequest in the following manner, the client waits for the ExplainLifecycleResponse to be returned before continuing with code execution:

ExplainLifecycleResponse response = client.indexLifecycle()
    .explainLifecycle(request, RequestOptions.DEFAULT);

Synchronous calls may throw an IOException in case of either failing to parse the REST response in the high-level REST client, the request times out or similar cases where there is no response coming back from the server.

In cases where the server returns a 4xx or 5xx error code, the high-level client tries to parse the response body error details instead and then throws a generic ElasticsearchException and adds the original ResponseException as a suppressed exception to it.

Asynchronous Execution

Executing a ExplainLifecycleRequest can also be done in an asynchronous fashion so that the client can return directly. Users need to specify how the response or potential failures will be handled by passing the request and a listener to the asynchronous ilm-explain-lifecycle method:

client.indexLifecycle().explainLifecycleAsync(request,
    RequestOptions.DEFAULT, listener); 

The ExplainLifecycleRequest to execute and the ActionListener to use when the execution completes

The asynchronous method does not block and returns immediately. Once it is completed the ActionListener is called back using the onResponse method if the execution successfully completed or using the onFailure method if it failed. Failure scenarios and expected exceptions are the same as in the synchronous execution case.

A typical listener for ilm-explain-lifecycle looks like:

ActionListener<ExplainLifecycleResponse> listener =
    new ActionListener<ExplainLifecycleResponse>() {
        @Override
        public void onResponse(ExplainLifecycleResponse response)
        {
            Map<String, IndexLifecycleExplainResponse> indices =
                response.getIndexResponses(); 
        }

        @Override
        public void onFailure(Exception e) {
            
        }
    };

Called when the execution is successfully completed.

Called when the whole ExplainLifecycleRequest fails.