[SOLR-7188] Run Data Import Handler processes in a SolrJ client

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Won't Fix
• Component/s: contrib - DataImportHandler
• Assignee: Unassigned
• Reporter: Ted Sullivan
• Created: 04/Mar/15 15:02
• Updated: 29/Aug/20 19:53
• Resolved: 29/Aug/20 19:53

Description

Adds a DataImportHandlerClient class that wraps an EmbeddedSolrServer and adds a DIHCloudWriter implementation of DIHWriter that sends documents to a remote SolrCloud cluster. This enables existing DIH processes to run outside of the Solr JVM which should enable better scalability.

The current architecture of DIH imposes several restrictions on scalability. First, the DIH runs in the same process space as Solr itself and competes for resources (CPU and memory) with normal Solr processes devoted to indexing and querying. Second, the DIH cannot be multi-threaded which means that parallelizing it requires splitting the processing amongst nodes in a SolrCloud cluster. Since the incoming data is sent through an UpdateRequestProcessor chain (via the SolrWriter implementation of DIHWriter), additional routing is done internally as the documents are forwarded to the current shard leader nodes once the ID hash is computed. This causes additional network traffic within the SolrCloud cluster. Scaling the DIH is limited by the number of nodes in the cluster and any heavy-duty processing due to entity processors or transformation elements shares the processing resources of Solr itself. This is known to be a source of bottlenecks in Solr installations (SolrCloud or Master-Slave) that use DIH.

The DataImportHandlerClient uses native DIH functionality - DataImporter, etc. but can be run externally to Solr. This means that as many processes as are needed to achieve necessary performance at scale can be added and the processing that occurs within the DataImportHandler is done outside of the Solr JVM. The same benefits that accrue with multiple SolrJ clients can now be realized with DIH without the necessity of porting code from DIH to a SolrJ client.

Issue Links

• duplicates: SOLR-853 Make DIH API friendly
• is related to: SOLR-4058 DIH should use the SolrCloudServer impl when running in SolrCloud mode.
• is related to: SOLR-9908 create SolrCloudDIHWriter to speedup DataImportHandler on SolrCloud
• is superceded by: SOLR-14783 Remove DIH from 9.0