Clear Cache API

Clear Cache Request

A ClearIndicesCacheRequest can be applied to one or more indices, or even on _all the indices:

ClearIndicesCacheRequest request = new ClearIndicesCacheRequest("index1"); 
ClearIndicesCacheRequest requestMultiple = new ClearIndicesCacheRequest("index1", "index2"); 
ClearIndicesCacheRequest requestAll = new ClearIndicesCacheRequest(); 

Clears the cache of one index

Clears the cache of multiple indices

Clears the cache of all the indices

Optional arguments

request.indicesOptions(IndicesOptions.lenientExpandOpen()); 

Setting IndicesOptions controls how unavailable indices are resolved and how wildcard expressions are expanded

request.queryCache(true); 

Set the query flag to true

request.fieldDataCache(true); 

Set the fielddata flag to true

request.requestCache(true); 

Set the request flag to true

request.fields("field1", "field2", "field3"); 

Set the fields parameter

Synchronous Execution

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

ClearIndicesCacheResponse clearCacheResponse = client.indices().clearCache(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 ClearIndicesCacheRequest 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 clear-cache method:

client.indices().clearCacheAsync(request, RequestOptions.DEFAULT, listener); 

The ClearIndicesCacheRequest 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 clear-cache looks like:

ActionListener<ClearIndicesCacheResponse> listener = new ActionListener<ClearIndicesCacheResponse>() {
    @Override
    public void onResponse(ClearIndicesCacheResponse clearCacheResponse) {
        
    }

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

Called when the execution is successfully completed.

Called when the whole ClearIndicesCacheRequest fails.

Clear Cache Response

The returned ClearIndicesCacheResponse allows to retrieve information about the executed operation as follows:

int totalShards = clearCacheResponse.getTotalShards(); 
int successfulShards = clearCacheResponse.getSuccessfulShards(); 
int failedShards = clearCacheResponse.getFailedShards(); 
DefaultShardOperationFailedException[] failures = clearCacheResponse.getShardFailures(); 

Total number of shards hit by the clear cache request

Number of shards where the clear cache has succeeded

Number of shards where the clear cache has failed

A list of failures if the operation failed on one or more shards

By default, if the indices were not found, an ElasticsearchException will be thrown:

try {
    ClearIndicesCacheRequest request = new ClearIndicesCacheRequest("does_not_exist");
    client.indices().clearCache(request, RequestOptions.DEFAULT);
} catch (ElasticsearchException exception) {
    if (exception.status() == RestStatus.NOT_FOUND) {
        
    }
}

Do something if the indices to be cleared were not found