Reindex API

Reindex Request

A ReindexRequest can be used to copy documents from one or more indexes into a destination index.

It requires an existing source index and a target index which may or may not exist pre-request. Reindex does not attempt to set up the destination index. It does not copy the settings of the source index. You should set up the destination index prior to running a _reindex action, including setting up mappings, shard counts, replicas, etc.

The simplest form of a ReindexRequest looks like follows:

ReindexRequest request = new ReindexRequest(); 
request.setSourceIndices("source1", "source2"); 
request.setDestIndex("dest");  

Creates the ReindexRequest

Adds a list of sources to copy from

Adds the destination index

The dest element can be configured like the index API to control optimistic concurrency control. Just leaving out versionType (as above) or setting it to internal will cause Elasticsearch to blindly dump documents into the target. Setting versionType to external will cause Elasticsearch to preserve the version from the source, create any documents that are missing, and update any documents that have an older version in the destination index than they do in the source index.

request.setDestVersionType(VersionType.EXTERNAL); 

Set the versionType to EXTERNAL

Setting opType to create will cause _reindex to only create missing documents in the target index. All existing documents will cause a version conflict. The default opType is index.

request.setDestOpType("create"); 

Set the opType to create

By default version conflicts abort the _reindex process but you can just count them by settings it to proceed in the request body

request.setConflicts("proceed"); 

Set proceed on version conflict

You can limit the documents by adding a type to the source or by adding a query.

request.setSourceDocTypes("doc"); 
request.setSourceQuery(new TermQueryBuilder("user", "kimchy")); 

Only copy doc type

Only copy documents which have field user set to kimchy

It’s also possible to limit the number of processed documents by setting size.

request.setSize(10); 

Only copy 10 documents

By default _reindex uses batches of 1000. You can change the batch size with sourceBatchSize.

request.setSourceBatchSize(100); 

Use batches of 100 documents

Reindex can also use the ingest feature by specifying a pipeline.

request.setDestPipeline("my_pipeline"); 

set pipeline to my_pipeline

If you want a particular set of documents from the source index you’ll need to use sort. If possible, prefer a more selective query to size and sort.

request.addSortField("field1", SortOrder.DESC); 
request.addSortField("field2", SortOrder.ASC); 

add descending sort to`field1`

add ascending sort to field2

ReindexRequest also supports a script that modifies the document. It allows you to also change the document’s metadata. The following example illustrates that.

request.setScript(
    new Script(
        ScriptType.INLINE, "painless",
        "if (ctx._source.user == 'kimchy') {ctx._source.likes++;}",
        Collections.emptyMap())); 

setScript to increment the likes field on all documents with user kimchy.

ReindexRequest supports reindexing from a remote Elasticsearch cluster. When using a remote cluster the query should be specified inside the RemoteInfo object and not using setSourceQuery. If both the remote info and the source query are set it results in a validation error during the request. The reason for this is that the remote Elasticsearch may not understand queries built by the modern query builders. The remote cluster support works all the way back to Elasticsearch 0.90 and the query language has changed since then. When reaching older versions, it is safer to write the query by hand in JSON.

request.setRemoteInfo(
    new RemoteInfo(
        "https", "localhost", 9002, null, new BytesArray(new MatchAllQueryBuilder().toString()),
        "user", "pass", Collections.emptyMap(), new TimeValue(100, TimeUnit.MILLISECONDS),
        new TimeValue(100, TimeUnit.SECONDS)
    )
); 

set remote elastic cluster

ReindexRequest also helps in automatically parallelizing using sliced-scroll to slice on _uid. Use setSlices to specify the number of slices to use.

request.setSlices(2); 

set number of slices to use

ReindexRequest uses the scroll parameter to control how long it keeps the "search context" alive.

request.setScroll(TimeValue.timeValueMinutes(10)); 

set scroll time

Optional arguments

In addition to the options above the following arguments can optionally be also provided:

request.setTimeout(TimeValue.timeValueMinutes(2)); 

Timeout to wait for the reindex request to be performed as a TimeValue

request.setRefresh(true); 

Refresh index after calling reindex

Synchronous Execution

BulkByScrollResponse bulkResponse = client.reindex(request, RequestOptions.DEFAULT);

Asynchronous Execution

The asynchronous execution of a reindex request requires both the ReindexRequest instance and an ActionListener instance to be passed to the asynchronous method:

client.reindexAsync(request, RequestOptions.DEFAULT, listener); 

The ReindexRequest 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.

A typical listener for BulkByScrollResponse looks like:

ActionListener<BulkByScrollResponse> listener = new ActionListener<BulkByScrollResponse>() {
    @Override
    public void onResponse(BulkByScrollResponse bulkResponse) {
        
    }

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

Called when the execution is successfully completed. The response is provided as an argument and contains a list of individual results for each operation that was executed. Note that one or more operations might have failed while the others have been successfully executed.

Called when the whole ReindexRequest fails. In this case the raised exception is provided as an argument and no operation has been executed.

Reindex Response

The returned BulkByScrollResponse contains information about the executed operations and allows to iterate over each result as follows:

TimeValue timeTaken = bulkResponse.getTook(); 
boolean timedOut = bulkResponse.isTimedOut(); 
long totalDocs = bulkResponse.getTotal(); 
long updatedDocs = bulkResponse.getUpdated(); 
long createdDocs = bulkResponse.getCreated(); 
long deletedDocs = bulkResponse.getDeleted(); 
long batches = bulkResponse.getBatches(); 
long noops = bulkResponse.getNoops(); 
long versionConflicts = bulkResponse.getVersionConflicts(); 
long bulkRetries = bulkResponse.getBulkRetries(); 
long searchRetries = bulkResponse.getSearchRetries(); 
TimeValue throttledMillis = bulkResponse.getStatus().getThrottled(); 
TimeValue throttledUntilMillis = bulkResponse.getStatus().getThrottledUntil(); 
List<ScrollableHitSource.SearchFailure> searchFailures = bulkResponse.getSearchFailures(); 
List<BulkItemResponse.Failure> bulkFailures = bulkResponse.getBulkFailures(); 

Get total time taken

Check if the request timed out

Get total number of docs processed

Number of docs that were updated

Number of docs that were created

Number of docs that were deleted

Number of batches that were executed

Number of skipped docs

Number of version conflicts

Number of times request had to retry bulk index operations

Number of times request had to retry search operations

The total time this request has throttled itself not including the current throttle time if it is currently sleeping

Remaining delay of any current throttle sleep or 0 if not sleeping

Failures during search phase

Failures during bulk index operation