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Battle of the Giants Apache Solr 4.0 vs ElasticSearch 0.20 Rafał Kuć – Sematext International @kucrafal @sematext sematext.com
Who Am I • „Solr 3.1 Cookbook" author (4.0 inc) • Sematext consultant & engineer • Solr.pl co-founder • Father and husband Copyright 2012 Sematext Int’l. All rights reserved
What Will I Talk About ? Copyright 2012 Sematext Int’l. All rights reserved
Under the Hood • ElasticSearch 0.20 – Apache Lucene 3.6.1 • Apache Solr 4.0 – Apache Lucene 4.0 Copyright 2012 Sematext Int’l. All rights reserved
Architecture • What we expect – Scalability – Fault toleranance – High availablity – Features • What we are also looking for – Manageability – Installation ease – Tools Copyright 2012 Sematext Int’l. All rights reserved
ElasticSearch Cluster Architecture • Distributed • Fault tolerant • Only ElasticSearch nodes • Single leader • Automatic leader election Copyright 2012 Sematext Int’l. All rights reserved
SolrCloud Cluster Architecture • Distributed • Fault tolerant • Apache Solr + ZooKeeper ensemble • Leader per shard • Automatic leader election Copyright 2012 Sematext Int’l. All rights reserved
Collection vs Index • Collection – Solr main logical index • Index – ElasticSearch main logic structure • Collections and Indices can be spread among different nodes in the cluster Copyright 2012 Sematext Int’l. All rights reserved
Multiple Document Types in Index • ElasticSearch - multiple document types in a single index • Apache Solr - multiple document types in a single collection – shared schema.xml Copyright 2012 Sematext Int’l. All rights reserved
Shards and Replicas • Index / Collection can have many shards • Each shard can have 0 or more replicas • Replicas are automatically updated • Replicas can be promoted to leaders when a leader shard goes off-line Copyright 2012 Sematext Int’l. All rights reserved
Index and Query Routing • Control where documents are going • Control where queries are going • Manual data distribution Copyright 2012 Sematext Int’l. All rights reserved
Querying Without Routing Shard 1 Shard 2 Shard 3 Shard 4 Shard 5 Shard 6 Shard 7 Shard 8 Collection / Index Application Copyright 2012 Sematext Int’l. All rights reserved
Query With Routing Shard 1 Shard 2 Shard 3 Shard 4 Shard 5 Shard 6 Shard 7 Shard 8 Collection / Index Application Copyright 2012 Sematext Int’l. All rights reserved
Routing Docs and Queries in Solr • Requires some effort • Defaults to hash based on document identifiers • Can be turned off using solr.NoOpDistributingUpdateProcessorFactory <updateRequestProcessorChain> <processor class="solr.LogUpdateProcessorFactory" /> <processor class="solr.RunUpdateProcessorFactory" /> <processor class="solr.NoOpDistributingUpdateProcessorFactory" /> </updateRequestProcessorChain> Copyright 2012 Sematext Int’l. All rights reserved
Routing Docs and Queries - ElasticSearch • routing parameter controls target shard which document/query will be forwarded to • defaults to document identifiers • can be changed to any value curl -XPUT localhost:9200/sematext/test/1?routing=1234 -d '{ "title" : "Test routing document" }' curl –XGET localhost:9200/sematext/test/_search/?q=*&routing=1234 Copyright 2012 Sematext Int’l. All rights reserved
Apache Solr Index Structure • Field types defined in schema.xml file • Fields defined in schema.xml file • Allows automatic value copying • Allows dynamic fields • Allows custom similarity definition Copyright 2012 Sematext Int’l. All rights reserved
ElasticSearch Index Structure • Schema - less • Analyzers and filters defined with HTTP API • Fields defined with an HTTP request • Multi – field support • Allows nested documents • Allows parent – child relationship • Allows structured data Copyright 2012 Sematext Int’l. All rights reserved
Index Structure Manipulation • Possible to some extent in Solr as well as ElasticSearch • ElasticSearch allows dynamic mappings update (not always) Copyright 2012 Sematext Int’l. All rights reserved
Aliasing • Solr – Allows core aliasing • ElasticSearch – Allows index aliasing – We can add filter to alias – We can add index routing – We can add search routing Copyright 2012 Sematext Int’l. All rights reserved
Server Configuration • Solr • ElasticSearch – Static in solrconfig.xml – Static in elasticsearch.yml – Can be reloaded – Properties can be during runtime with changed during runtime collection/core reload (although not all) without reloading Copyright 2012 Sematext Int’l. All rights reserved
ElasticSearch Gateway Module • Your data time machine • Stores indices and meta data • Currently available: – Local – Shared FS – Hadoop – S3 Copyright 2012 Sematext Int’l. All rights reserved
Discovery • Apache Solr uses ZooKeeper • ElasticSearch uses Zen Discovery Copyright 2012 Sematext Int’l. All rights reserved
ElasticSearch Zen Discovery • Allows automatic node discovery • Provides multicast and unicast discovery methods • Automatic master detection • Two - way failure detection Copyright 2012 Sematext Int’l. All rights reserved
Apache Solr & Apache ZooKeeper • Requires additional software • ZooKeeper ensemble with 1+ ZooKeeper instances • Prevents split – brain situations • Holds collections configurations • Solr needs to know address of one of the ZooKeeper instances Copyright 2012 Sematext Int’l. All rights reserved
API • HTTP REST API in ElasticSearch or Query String for simple queries • HTTP with Query String in Apache Solr • Both provide specialized Java API – SolrJ for Apache Solr and CloudSolrServer – ElasticSearch with TransportClient for remote connections Copyright 2012 Sematext Int’l. All rights reserved
Apache Solr and Query String • Queries are built of request parameters • Some degree of structuring allowed (local params) curl 'http://localhost:8983/solr/select?q=text:weird&sort=date+desc' Copyright 2012 Sematext Int’l. All rights reserved
ElasticSearch REST End-Points • Simple queries built of request parameters • Stuctured queries built as JSON objects curl –XGET 'localhost:9200/sematext/test/_search/?q=_all:weird&sort=date:desc' curl -XGET 'localhost:9200/sematext/test_search' -d '{ "query" : { "term" : { "_all" : "weird" }, "sort" : { "date" : { "order" : "desc" } } }' Copyright 2012 Sematext Int’l. All rights reserved
Data Handling • Solr – Multiple formats allowed as input – Can return results in multiple formats • ElasticSearch – JSON in / JSON out Copyright 2012 Sematext Int’l. All rights reserved
Single or Batch • Solr • ElasticSearch – Single or multiple – Single document with a documents per standard indexing call request – _bulk end – point exposed for batch indexing – _bulk UDP end – point can be exposed for low latency batch indexing Copyright 2012 Sematext Int’l. All rights reserved
Partial Document Updates • Not based on LUCENE-3837 proposed by Andrzej Białecki • Document reindexing on the side of search server • Both servers use versioning to prevent changes being overwritten • Can lead to decreased network traffic in some cases Copyright 2012 Sematext Int’l. All rights reserved
ElasticSearch Partial Doc Update • Special end – point exposed - _update • Supports parameters like routing, parent, replication, percolate, etc (similar to Index API) • Uses scripts to perform document updates curl -XPOST 'localhost:9200/sematext/test/12345/_update' -d '{ "script" : "ctx._source.enabled = enabled", "params" : { "enabled" : true } }' Copyright 2012 Sematext Int’l. All rights reserved
Apache Solr Partial Doc Update • Sent to the standard update handler • Requires _version_ field to be present curl 'localhost:8983/solr/update?commit=true' -H 'Content- type:application/json' -d '[ { "id" : "12345", "enabled" : { "set" : true } } ]' Copyright 2012 Sematext Int’l. All rights reserved
Solr Collections API • Built on top of Core Admin • Allows: – Collection creation – Collection reload – Collection deletion Copyright 2012 Sematext Int’l. All rights reserved
ElasticSearch Indices REST API • Allows: – Index creation – Index deletion – Index closing and opening – Index refreshing – Existence checking Copyright 2012 Sematext Int’l. All rights reserved
Analysis Chain Definition • Solr • ElasticSearch – Static in schema.xml – Static in elasticsearch.yml – Can be reloaded – Defined during index/type during runtime with creation with REST call collection/core reload – Possible to change with update mapping call (not all changes allowed) Copyright 2012 Sematext Int’l. All rights reserved
Multilingual Data Handling • Both ElasticSearch and Apache Solr built on top of Apache Lucene • Solr – analyzers defined per field in schema.xml file • ElasticSearch – analyzer defined in mappings, but can be set during query or specified on the basis of field values Copyright 2012 Sematext Int’l. All rights reserved
Results Grouping • Available in Apache Solr only • Allows for results grouping based on: – Field value – Query – Function query (not available during distributed searching) Copyright 2012 Sematext Int’l. All rights reserved
Prospective Search • Allows for checking if a document matches a stored query • Not available in Apache Solr • Available in ElasticSearch under the name of Percolator Copyright 2012 Sematext Int’l. All rights reserved
Spellchecker • Allows to check and correct spelling mistakes • Not available in ElasticSearch currently • Multiple implementations available in Apache Solr – IndexBasedSpellChecker – WordBreakSolrSpellChecker – DirectSolrSpellChecker Copyright 2012 Sematext Int’l. All rights reserved
Full Text Search Capabilities • Variety of queries • Ability to control score calculation • Different query parsers available • Advanced Lucene queries (like SpanQueries) exposed Copyright 2012 Sematext Int’l. All rights reserved
Score Calculation • Leverage Lucene scoring capabilities • Control over document importance • Control over query importance • Control over term and phrase importance Copyright 2012 Sematext Int’l. All rights reserved
Apache Solr and Score Influence • Index time – Document boosts – Field boosts • Query time – Term boosts – Field boosts – Phrases boost – Function queries Copyright 2012 Sematext Int’l. All rights reserved
ElasticSearch and Score Influence • Index time – Document and field boosts • Query time – Different queries provide different boost controls – Can calculate distributed term frequencies – Negative and Positive boosting queries – Custom score filters • Scripts – Control scoring with scripts Copyright 2012 Sematext Int’l. All rights reserved
Nested Objects • Possible only in ElasticSearch • Indexed as separate documents • Stored in the same part of the index as the root document • Hidden from standard queries and filters • Need appropriate queries and filters (nested) Copyright 2012 Sematext Int’l. All rights reserved
More Like This • Lets us find similar documents • Solr – More Like This Component • ElasticSearch – More Like This Query – More Like This Field Query – _mlt REST end – point Copyright 2012 Sematext Int’l. All rights reserved
Solr Parent – Child Relationship • Used at query time • Multi core joins possible http://localhost:8983/solr/select?q={!join from=parent to=id}color:Yellow Copyright 2012 Sematext Int’l. All rights reserved
ElasticSearch Parent – Child Handling • Proper indexing required • Indexed as separate documents • Standard queries don’t return child documents • In order to retrieve parent docs one should use appropriate queries and filters (has_child, has_parent, top_children) Copyright 2012 Sematext Int’l. All rights reserved
Filters • Used to narrown down query results • Good candidates for caching and reuse • Supported by ElasticSearch and Apache Solr • Should be used for repeatable query elements Copyright 2012 Sematext Int’l. All rights reserved
Apache Solr Filter Queries • Multiple filters per query • Filters are addictive • Different query parsers can be used • Local params can be used • Narrow down faceting results Copyright 2012 Sematext Int’l. All rights reserved
ElasticSearch Filtered Queries • Can be defined using queries exposed by the Query DSL • Can be used for custom score calculation (i.e., custom filters score query) • Doesn’t narrow down faceting results by default (facets have their own filters) Copyright 2012 Sematext Int’l. All rights reserved
Filter Cache Control • Both Solr and ElasticSearch let us control cache for filters • Solr – Using local params and cache property • ElasticSearch – _cache property – _cache_key property Copyright 2012 Sematext Int’l. All rights reserved
Faceting • Both provide common facets – Terms – Range & query – Terms statistics – Spatial distance • Solr – Pivot faceting • ElasticSearch – Histograms Copyright 2012 Sematext Int’l. All rights reserved
Real Time Or Not ? • Allow getting document not yet indexed • Don’t need searcher reopening • ElasticSearch – Separate Get and Multi Get API’s • Apache Solr – Separate Realtime Get Handler – Can be used as a search component Copyright 2012 Sematext Int’l. All rights reserved
Caches and Warming • ElasticSearch and Solr allow caching • Both allow running warming queries • ElasticSearch by default doesn’t limit cache sizes Copyright 2012 Sematext Int’l. All rights reserved
Solr Caches • Types – Filter Cache – Query Result Cache – Document Cache • Implementation choices – LRUCache – FastLRUCache – LFUCache • Other configuration options: – Size – Maximum size – Autowarming count Copyright 2012 Sematext Int’l. All rights reserved
ElasticSearch Caches • Types – Filter Cache – Field Data Cache • Implementation choices – Resident – Soft – Weak • Other configuration options: – Max size (entries per segment) – Expiration time Copyright 2012 Sematext Int’l. All rights reserved
Cluster State Monitoring • Apache Solr – multiple mbeans exposed by JMX • ElasticSearch – multiple REST end – points exposed to get different statistics Copyright 2012 Sematext Int’l. All rights reserved
ElasticSearch Statistics API • Health and State Check • Nodes Information and Statistics • Cache Statistics • Index Segments Information • Index Information and Statistics • Mappings Information Copyright 2012 Sematext Int’l. All rights reserved
Cluster Monitoring Copyright 2012 Sematext Int’l. All rights reserved
Cluster Monitoring with SPM Copyright 2012 Sematext Int’l. All rights reserved
Cluster Settings Update • ElasticSearch lets us: – Control rebalancing – Control recovery – Control allocation – Change the above on the live cluster Copyright 2012 Sematext Int’l. All rights reserved
Custom Shard Allocation • Possible in ElasticSearch • Cluster level: curl -XPUT localhost:9200/_cluster/settings -d '{ "persistent" : { "cluster.routing.allocation.exclude._ip" : "192.168.2.1" } }' • Index level: curl -XPUT localhost:9200/sematext/ -d '{ "index.routing.allocation.include.tag" : "nodeOne,nodeTwo" }' Copyright 2012 Sematext Int’l. All rights reserved
Moving Shards and Replicas • Possible in ElasticSearch, not available in Solr • Allows to move shards and replicas to any node in the cluster on demand • Available in ElasticSearch: curl -XPOST 'localhost:9200/_cluster/reroute' -d '{ "commands" : [ {"move" : {"index" : "sematext", "shard" : 0, "from_node" : "node1", "to_node" : "node2"}}, {"allocate" : {"index" : "sematext", "shard" : 1, "node" : "node3"}} ] }' Copyright 2012 Sematext Int’l. All rights reserved
And The Winner Is ? Copyright 2012 Sematext Int’l. All rights reserved
How to Reach Us • Rafał Kuć – Twitter: @kucrafal – E-mail: rafal.kuc@sematext.com • Sematext – Twitter: @sematext – Website: http://sematext.com • Solr vs ElasticSearch series: • http://blog.sematext.com/2012/08/23/solr-vs- elasticsearch-part-1-overview/ Copyright 2012 Sematext Int’l. All rights reserved
We Are Hiring ! • Dig Search ? • Dig Analytics ? • Dig Big Data ? • Dig Performance ? • Dig working with and in open – source ? • We’re hiring world – wide ! http://sematext.com/about/jobs.html Copyright 2012 Sematext Int’l. All rights reserved