- Elasticsearch Guide: other versions:
- Getting Started
- Set up Elasticsearch
- Installing Elasticsearch
- Configuring Elasticsearch
- Important Elasticsearch configuration
- Important System Configuration
- Bootstrap Checks
- Heap size check
- File descriptor check
- Memory lock check
- Maximum number of threads check
- Max file size check
- Maximum size virtual memory check
- Maximum map count check
- Client JVM check
- Use serial collector check
- System call filter check
- OnError and OnOutOfMemoryError checks
- Early-access check
- G1GC check
- All permission check
- Starting Elasticsearch
- Stopping Elasticsearch
- Adding nodes to your cluster
- Installing X-Pack
- Set up X-Pack
- Configuring X-Pack Java Clients
- X-Pack Settings
- Bootstrap Checks for X-Pack
- Upgrade Elasticsearch
- API Conventions
- Document APIs
- Search APIs
- Aggregations
- Metrics Aggregations
- Avg Aggregation
- Cardinality Aggregation
- Extended Stats Aggregation
- Geo Bounds Aggregation
- Geo Centroid Aggregation
- Max Aggregation
- Min Aggregation
- Percentiles Aggregation
- Percentile Ranks Aggregation
- Scripted Metric Aggregation
- Stats Aggregation
- Sum Aggregation
- Top Hits Aggregation
- Value Count Aggregation
- Bucket Aggregations
- Adjacency Matrix Aggregation
- Children Aggregation
- Composite Aggregation
- Date Histogram Aggregation
- Date Range Aggregation
- Diversified Sampler Aggregation
- Filter Aggregation
- Filters Aggregation
- Geo Distance Aggregation
- GeoHash grid Aggregation
- Global Aggregation
- Histogram Aggregation
- IP Range Aggregation
- Missing Aggregation
- Nested Aggregation
- Range Aggregation
- Reverse nested Aggregation
- Sampler Aggregation
- Significant Terms Aggregation
- Significant Text Aggregation
- Terms Aggregation
- Pipeline Aggregations
- Avg Bucket Aggregation
- Derivative Aggregation
- Max Bucket Aggregation
- Min Bucket Aggregation
- Sum Bucket Aggregation
- Stats Bucket Aggregation
- Extended Stats Bucket Aggregation
- Percentiles Bucket Aggregation
- Moving Average Aggregation
- Cumulative Sum Aggregation
- Bucket Script Aggregation
- Bucket Selector Aggregation
- Bucket Sort Aggregation
- Serial Differencing Aggregation
- Matrix Aggregations
- Caching heavy aggregations
- Returning only aggregation results
- Aggregation Metadata
- Returning the type of the aggregation
- Metrics Aggregations
- Indices APIs
- Create Index
- Delete Index
- Get Index
- Indices Exists
- Open / Close Index API
- Shrink Index
- Split Index
- Rollover Index
- Put Mapping
- Get Mapping
- Get Field Mapping
- Types Exists
- Index Aliases
- Update Indices Settings
- Get Settings
- Analyze
- Index Templates
- Indices Stats
- Indices Segments
- Indices Recovery
- Indices Shard Stores
- Clear Cache
- Flush
- Refresh
- Force Merge
- cat APIs
- Cluster APIs
- Query DSL
- Mapping
- Analysis
- Anatomy of an analyzer
- Testing analyzers
- Analyzers
- Normalizers
- Tokenizers
- Standard Tokenizer
- Letter Tokenizer
- Lowercase Tokenizer
- Whitespace Tokenizer
- UAX URL Email Tokenizer
- Classic Tokenizer
- Thai Tokenizer
- NGram Tokenizer
- Edge NGram Tokenizer
- Keyword Tokenizer
- Pattern Tokenizer
- Simple Pattern Tokenizer
- Simple Pattern Split Tokenizer
- Path Hierarchy Tokenizer
- Path Hierarchy Tokenizer Examples
- Token Filters
- Standard Token Filter
- ASCII Folding Token Filter
- Flatten Graph Token Filter
- Length Token Filter
- Lowercase Token Filter
- Uppercase Token Filter
- NGram Token Filter
- Edge NGram Token Filter
- Porter Stem Token Filter
- Shingle Token Filter
- Stop Token Filter
- Word Delimiter Token Filter
- Word Delimiter Graph Token Filter
- Stemmer Token Filter
- Stemmer Override Token Filter
- Keyword Marker Token Filter
- Keyword Repeat Token Filter
- KStem Token Filter
- Snowball Token Filter
- Phonetic Token Filter
- Synonym Token Filter
- Synonym Graph Token Filter
- Compound Word Token Filters
- Reverse Token Filter
- Elision Token Filter
- Truncate Token Filter
- Unique Token Filter
- Pattern Capture Token Filter
- Pattern Replace Token Filter
- Trim Token Filter
- Limit Token Count Token Filter
- Hunspell Token Filter
- Common Grams Token Filter
- Normalization Token Filter
- CJK Width Token Filter
- CJK Bigram Token Filter
- Delimited Payload Token Filter
- Keep Words Token Filter
- Keep Types Token Filter
- Classic Token Filter
- Apostrophe Token Filter
- Decimal Digit Token Filter
- Fingerprint Token Filter
- Minhash Token Filter
- Character Filters
- Modules
- Index Modules
- Ingest Node
- Pipeline Definition
- Ingest APIs
- Accessing Data in Pipelines
- Handling Failures in Pipelines
- Processors
- Append Processor
- Convert Processor
- Date Processor
- Date Index Name Processor
- Fail Processor
- Foreach Processor
- Grok Processor
- Gsub Processor
- Join Processor
- JSON Processor
- KV Processor
- Lowercase Processor
- Remove Processor
- Rename Processor
- Script Processor
- Set Processor
- Split Processor
- Sort Processor
- Trim Processor
- Uppercase Processor
- Dot Expander Processor
- URL Decode Processor
- SQL Access
- Monitor a cluster
- Rolling up historical data
- Secure a cluster
- Overview
- Configuring security
- Encrypting communications in Elasticsearch
- Encrypting communications in an Elasticsearch Docker container
- Enabling cipher suites for stronger encryption
- Separating node-to-node and client traffic
- Configuring an Active Directory realm
- Configuring a file realm
- Configuring an LDAP realm
- Configuring a native realm
- Configuring a PKI realm
- Configuring a SAML realm
- Security settings
- Auditing settings
- Getting started with security
- How security works
- User authentication
- Configuring SAML single-sign-on on the Elastic Stack
- User authorization
- Auditing security events
- Encrypting communications
- Restricting connections with IP filtering
- Cross cluster search, tribe, clients, and integrations
- Reference
- Troubleshooting
- Can’t log in after upgrading to 6.3.2
- Some settings are not returned via the nodes settings API
- Authorization exceptions
- Users command fails due to extra arguments
- Users are frequently locked out of Active Directory
- Certificate verification fails for curl on Mac
- SSLHandshakeException causes connections to fail
- Common SSL/TLS exceptions
- Common SAML issues
- Internal Server Error in Kibana
- Setup-passwords command fails due to connection failure
- Failures due to relocation of the configuration files
- Limitations
- Alerting on Cluster and Index Events
- X-Pack APIs
- Info API
- Explore API
- Licensing APIs
- Migration APIs
- Machine Learning APIs
- Add Events to Calendar
- Add Jobs to Calendar
- Close Jobs
- Create Calendar
- Create Datafeeds
- Create Jobs
- Delete Calendar
- Delete Datafeeds
- Delete Events from Calendar
- Delete Jobs
- Delete Jobs from Calendar
- Delete Model Snapshots
- Flush Jobs
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- Get Calendars
- Get Buckets
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- Get Influencers
- Get Jobs
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- Get Scheduled Events
- Get Records
- Open Jobs
- Post Data to Jobs
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- Revert Model Snapshots
- Start Datafeeds
- Stop Datafeeds
- Update Datafeeds
- Update Jobs
- Update Model Snapshots
- Rollup APIs
- Security APIs
- Authenticate API
- Change passwords API
- Clear Cache API
- Create or update role mappings API
- Clear roles cache API
- Create or update roles API
- Create or update users API
- Delete role mappings API
- Delete roles API
- Delete users API
- Disable users API
- Enable users API
- Get role mappings API
- Get roles API
- Get token API
- Get users API
- Privilege APIs
- Invalidate token API
- SSL Certificate API
- Watcher APIs
- Definitions
- Command line tools
- How To
- Testing
- Glossary of terms
- Release Highlights
- Breaking changes
- Release Notes
- Elasticsearch version 6.3.2
- Elasticsearch version 6.3.1
- Elasticsearch version 6.3.0
- Elasticsearch version 6.2.4
- Elasticsearch version 6.2.3
- Elasticsearch version 6.2.2
- Elasticsearch version 6.2.1
- Elasticsearch version 6.2.0
- Elasticsearch version 6.1.4
- Elasticsearch version 6.1.3
- Elasticsearch version 6.1.2
- Elasticsearch version 6.1.1
- Elasticsearch version 6.1.0
- Elasticsearch version 6.0.1
- Elasticsearch version 6.0.0
- Elasticsearch version 6.0.0-rc2
- Elasticsearch version 6.0.0-rc1
- Elasticsearch version 6.0.0-beta2
- Elasticsearch version 6.0.0-beta1
- Elasticsearch version 6.0.0-alpha2
- Elasticsearch version 6.0.0-alpha1
- Elasticsearch version 6.0.0-alpha1 (Changes previously released in 5.x)
Shard Allocation Awareness
editShard Allocation Awareness
editWhen running nodes on multiple VMs on the same physical server, on multiple racks, or across multiple zones or domains, it is more likely that two nodes on the same physical server, in the same rack, or in the same zone or domain will crash at the same time, rather than two unrelated nodes crashing simultaneously.
If Elasticsearch is aware of the physical configuration of your hardware, it can ensure that the primary shard and its replica shards are spread across different physical servers, racks, or zones, to minimise the risk of losing all shard copies at the same time.
The shard allocation awareness settings allow you to tell Elasticsearch about your hardware configuration.
As an example, let’s assume we have several racks. When we start a node, we
can tell it which rack it is in by assigning it an arbitrary metadata
attribute called rack_id
— we could use any attribute name. For example:
Now, we need to set up shard allocation awareness by telling Elasticsearch
which attributes to use. This can be configured in the elasticsearch.yml
file on all master-eligible nodes, or it can be set (and changed) with the
cluster-update-settings API.
For our example, we’ll set the value in the config file:
cluster.routing.allocation.awareness.attributes: rack_id
With this config in place, let’s say we start two nodes with
node.attr.rack_id
set to rack_one
, and we create an index with 5 primary
shards and 1 replica of each primary. All primaries and replicas are
allocated across the two nodes.
Now, if we start two more nodes with node.attr.rack_id
set to rack_two
,
Elasticsearch will move shards across to the new nodes, ensuring (if possible)
that no two copies of the same shard will be in the same rack. However if
rack_two
were to fail, taking down both of its nodes, Elasticsearch will
still allocate the lost shard copies to nodes in rack_one
.
Multiple awareness attributes can be specified, in which case each attribute is considered separately when deciding where to allocate the shards.
cluster.routing.allocation.awareness.attributes: rack_id,zone
When using awareness attributes, shards will not be allocated to nodes that don’t have values set for those attributes.
Number of primary/replica of a shard allocated on a specific group of nodes with the same awareness attribute value is determined by the number of attribute values. When the number of nodes in groups is unbalanced and there are many replicas, replica shards may be left unassigned.
Forced Awareness
editImagine that you have two zones and enough hardware across the two zones to host all of your primary and replica shards. But perhaps the hardware in a single zone, while sufficient to host half the shards, would be unable to host ALL the shards.
With ordinary awareness, if one zone lost contact with the other zone, Elasticsearch would assign all of the missing replica shards to a single zone. But in this example, this sudden extra load would cause the hardware in the remaining zone to be overloaded.
Forced awareness solves this problem by NEVER allowing copies of the same shard to be allocated to the same zone.
For example, lets say we have an awareness attribute called zone
, and we
know we are going to have two zones, zone1
and zone2
. Here is how we can
force awareness on a node:
cluster.routing.allocation.awareness.force.zone.values: zone1,zone2 cluster.routing.allocation.awareness.attributes: zone
Now, if we start 2 nodes with node.attr.zone
set to zone1
and create an
index with 5 shards and 1 replica. The index will be created, but only the 5
primary shards will be allocated (with no replicas). Only when we start more
nodes with node.attr.zone
set to zone2
will the replicas be allocated.
The cluster.routing.allocation.awareness.*
settings can all be updated
dynamically on a live cluster with the
cluster-update-settings API.
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