Post on 08-Sep-2014
description
Scaling Massive ElasticSearch
Clusters
Rafał Kuć – Sematext International
@kucrafal @sematext sematext.com
Who Am I
• „Solr 3.1 Cookbook” author
• Sematext software engineer
• Solr.pl co-founder
• Father and husband :-)
Copyright 2012 Sematext Int’l. All rights reserved
What Will I Talk About ?
• ElasticSearch scaling
• Indexing thousands of documents per second
• Performing queries in tens of milliseconds
• Controling shard and replica placement
• Handling multilingual content
• Performance testing
• Cluster monitoring
Copyright 2012 Sematext Int’l. All rights reserved
The Challenge
• More than 50 millions of documents a day
• Real time search
• Less than 200ms average query latency
• Throughput of at least 1000 QPS
• Multilingual indexing
• Multilingual querying
Copyright 2012 Sematext Int’l. All rights reserved
Why ElasticSearch ?
• Written with NRT and cloud support in mind
• Uses Lucene and all its goodness
• Distributed indexing with document
distribution control out of the box
• Easy index, shard and replicas creation on live
cluster
Copyright 2012 Sematext Int’l. All rights reserved
Index Design
• Several indices (at least one index for each day
of data)
• Indices divided into multiple shards
• Multiple replicas of a single shard
• Real-time, synchronous replication
• Near-real-time index refresh (1 to 30 seconds)
Copyright 2012 Sematext Int’l. All rights reserved
Shard Deployment Problems
• Multiple shards per node
• Replicas on the same nodes as shards
• Not evenly distributed shards and replicas
• Some nodes being hot, while others are cold
Copyright 2012 Sematext Int’l. All rights reserved
Default Shard Deployment
ElasticSearch Cluster
Node 1 Node 2
Node 3
Shard 1 Shard 2 Shard 3 Replica 1
Replica 2
Replica 3
Copyright 2012 Sematext Int’l. All rights reserved
What Can We Do With Shards Then ?
• Contol shard placement with node tags:
– index.routing.allocation.include.tag
– index.routing.allocation.exclude.tag
• Control shard placement with nodes IP addresses:
– cluster.routing.allocation.include._ip
– cluster.routing.allocation.exclude._ip
• Specified on index or cluster level
• Can be changed on live cluster !
Copyright 2012 Sematext Int’l. All rights reserved
Shard Allocation Examples
• 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
Number of Shards Per Node
• Allows one to specify number of shards per
node
• Specified on index level
• Can be changed on live indices
• Example:
curl -XPUT localhost:9200/sematext -d '{
"index.routing.allocation.total_shards_per_node" : 2
}'
Copyright 2012 Sematext Int’l. All rights reserved
Controlled Shard Deployment
ElasticSearch Cluster
Node 1 Node 2
Node 3
Shard 1
Shard 2
Shard 3 Replica 1Replica 2
Replica 3
Copyright 2012 Sematext Int’l. All rights reserved
Does Routing Matters ?
• Controls target shard for each document
• Defaults to hash of a document identifier
• Can be specified explicitly (routing parameter) oras a field value (a bit less performant)
• Can take any value
• Example:
curl -XPUT localhost:9200/sematext/test/1?routing=1234 -d '{
"title" : "Test routing document"
}'
Copyright 2012 Sematext Int’l. All rights reserved
Indexing the Data
ElasticSearch Cluster
Node 1 Node 2
Node 3
Shard
1
Shard
2
Shard
3
Replica
1
Replica
2
Replica
3
Indexing application
Copyright 2012 Sematext Int’l. All rights reserved
How We Indexed Data
ElasticSearch Cluster
Node 1 Node 2
Shard 1 Shard 2
Node 3
Indexing application
Copyright 2012 Sematext Int’l. All rights reserved
Nodes Without Data
• Nodes used only to route data and queries to
other nodes in the cluster
• Such nodes don’t suffer from I/O waits (of
course Data Nodes don’t suffer from I/O waits
all the time)
• Not default ElasticSearch behavior
• Setup by setting node.data to false
Copyright 2012 Sematext Int’l. All rights reserved
Multilingual Indexing
• Detection of document's language before
sending it for indexing
• With, e.g. Sematext LangID or Apache Tika
• Set known language analyzers in configuration
or mappings
• Set analyzer during indexing (_analyzer field)
Copyright 2012 Sematext Int’l. All rights reserved
Multilingual Indexing Example
curl -XPUT localhost:9200/sematext/test/10 -d '{
"title" : "Test document",
"langId" : "english"
}'
{
"test" : {
"_analyzer" : { "path" : "langId" },
"properties" : {
"id" : { "type" : "long", "store" : "yes", "precision_step" : "0" },
"title" : { "type" : "string", "store" : "yes", "index" : "analyzed" },
"langId" : { "type" : "string", "store" : "yes", "index" : "not_analyzed" }
}
}
}
Copyright 2012 Sematext Int’l. All rights reserved
Multilingual Queries
• Identify language of query before its execution
(can be problematic)
• Query analyzer can be specified per query
(analyzer parameter):curl -XGET
localhost:9200/sematext/_search?q=let+AND+me&analyzer=english
Copyright 2012 Sematext Int’l. All rights reserved
Query Performance Factors – Lucene
level
• Refresh interval
– Defaults to 1 second
– Can be specified on cluster or index level
– curl -XPUT localhost:9200/_settings -d '{ "index" : { "refresh_interval" : "600s" } }'
• Merge factor
– Defaults to 10
– Can be specified on cluster or index level
– curl -XPUT localhost:9200/_settings -d '{ "index" : { "merge.policy.merge_factor" : 30 } }'
Copyright 2012 Sematext Int’l. All rights reserved
Let’s Talk About Routing Once Again
• Routes a query to a particular shard
• Speeds up queries depending on number of shards for a given index
• Have to be specified manualy with routingparameter during query
• routing parameter can take any value:
curl -XGET 'localhost:9200/sematext/_search?q=test&routing=2012-02-16'
Copyright 2012 Sematext Int’l. All rights reserved
Querying ElasticSearch – No Routing
Shard 1 Shard 2 Shard 3 Shard 4
Shard 5 Shard 6 Shard 7 Shard 8
ElasticSearch Index
Application
Copyright 2012 Sematext Int’l. All rights reserved
Shard 1 Shard 2 Shard 3 Shard 4
Shard 5 Shard 6 Shard 7 Shard 8
ElasticSearch Index
Application
Querying ElasticSearch – With Routing
Copyright 2012 Sematext Int’l. All rights reserved
Performance Numbers
Queries without routing (200 shards, 1 replica)
#threads Avg response time Throughput 90% line Median CPU Utilization
1 3169ms 19,0/min 5214ms 2692ms 95 – 99%
Queries with routing (200 shards, 1 replica)
#threads Avg response time Throughput 90% line Median CPU Utilization
10 196ms 50,6/sec 642ms 29ms 25 – 40%
20 218ms 91,2/sec 718ms 11ms 10 – 15%
Copyright 2012 Sematext Int’l. All rights reserved
Scaling Query Throughput – What Else ?
• Increasing the number of shards for data
distribution
• Increasing the number of replicas
• Using routing
• Avoid always hitting the same node and
hotspotting it
Copyright 2012 Sematext Int’l. All rights reserved
FieldCache and OutOfMemory
• ElasticSearch default setup doesn’t limit field
data cache size
Copyright 2012 Sematext Int’l. All rights reserved
FieldCache – What We Can do With It ?
• Keep its default type and set:– Maximum size (index.cache.field.max_size)
– Expiration time (index.cache.field.expire)
• Change its type:– soft (index.cache.field.type)
• Change your data:– Make your fields less precise (ie: dates)
– If you sort or facet on fields think if you can reducefields granularity
• Buy more servers :-)
Copyright 2012 Sematext Int’l. All rights reserved
FieldCache After Changes
Copyright 2012 Sematext Int’l. All rights reserved
Additional Problems We Encountered
• Rebalancing after full cluster restarts
– cluster.routing.allocation.disable_allocation
– cluster.routing.allocation.disable_replica_allocation
• Long startup and initialization
• Faceting with strings vs faceting on numbers on
high cardinality fields
Copyright 2012 Sematext Int’l. All rights reserved
JVM Optimization
• Remember to leave enough memory to OS for
cache
• Make GC frequent ans short vs. rare and long
– -XX:+UseParNewGC
– -XX:+UseConcMarkSweepGC
– -XX:+CMSParallelRemarkEnabled
• -XX:+AlwaysPreTouch (for short performance
tests)
Copyright 2012 Sematext Int’l. All rights reserved
Performance Testing
• Data
– How much data do I need ?
– Choosing the right queries
• Make changes
– One change at a time
– Understand the impact of the change
• Monitor your cluster (jstat, dstat/vmstat, SPM)
• Analyze your results
Copyright 2012 Sematext Int’l. All rights reserved
ElasticSearch Cluster Monitoring
• Cluster health
• Indexing statistics
• Query rate
• JVM memory and garbage collector work
• Cache usage
• Node memory and CPU usage
Copyright 2012 Sematext Int’l. All rights reserved
Cluster Health
Copyright 2012 Sematext Int’l. All rights reserved
Node restart
Indexing Statistics
Copyright 2012 Sematext Int’l. All rights reserved
Query Rate
Copyright 2012 Sematext Int’l. All rights reserved
JVM Memory and GC
Copyright 2012 Sematext Int’l. All rights reserved
Cache Usage
Copyright 2012 Sematext Int’l. All rights reserved
CPU and Memory
Copyright 2012 Sematext Int’l. All rights reserved
Summary
• Controlling shard and replica placement
• Indexing and querying multilingual data
• How to use sharding and routing and not to
tear your hair out
• How to test your cluster performance to find
bottle-necks
• How to monitor your cluster and find
problems right away
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
How to Reach Us
• Rafał Kuć
– Twitter: @kucrafal
– E-mail: rafal.kuc@sematext.com
• Sematext
– Twitter: @sematext
– Website: http://sematext.com
• Graphs used in the presentation are from:
– SPM for ElasticSearch (http://sematext.com/spm)
Copyright 2012 Sematext Int’l. All rights reserved
Thank You For Your Attention