- Elasticsearch Guide: other versions:
- Elasticsearch introduction
- Getting started with Elasticsearch
- 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
- Discovery configuration check
- Starting Elasticsearch
- Stopping Elasticsearch
- Adding nodes to your cluster
- Set up X-Pack
- Configuring X-Pack Java Clients
- Bootstrap Checks for X-Pack
- Upgrade Elasticsearch
- API conventions
- Document APIs
- Search APIs
- Aggregations
- Metrics Aggregations
- Avg Aggregation
- Weighted 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
- Median Absolute Deviation Aggregation
- Bucket Aggregations
- Adjacency Matrix Aggregation
- Auto-interval Date Histogram Aggregation
- Children Aggregation
- Composite Aggregation
- Date Histogram Aggregation
- Date Range Aggregation
- Diversified Sampler Aggregation
- Filter Aggregation
- Filters Aggregation
- Geo Distance Aggregation
- GeoHash grid Aggregation
- GeoTile Grid Aggregation
- Global Aggregation
- Histogram Aggregation
- IP Range Aggregation
- Missing Aggregation
- Nested Aggregation
- Parent 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
- Moving Function 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
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- Indices Recovery
- Indices Shard Stores
- Clear Cache
- Flush
- Refresh
- Force Merge
- cat APIs
- Cluster APIs
- Query DSL
- Scripting
- 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
- Char Group Tokenizer
- Simple Pattern Tokenizer
- Simple Pattern Split Tokenizer
- Path Hierarchy Tokenizer
- Path Hierarchy Tokenizer Examples
- Token Filters
- ASCII Folding Token Filter
- Flatten Graph Token Filter
- Length Token Filter
- Lowercase Token Filter
- Uppercase Token Filter
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- Edge NGram Token Filter
- Porter Stem Token Filter
- Shingle Token Filter
- Stop Token Filter
- Word Delimiter Token Filter
- Word Delimiter Graph Token Filter
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- Conditional Token Filter
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- Stemmer Token Filter
- Stemmer Override Token Filter
- Keyword Marker Token Filter
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- KStem Token Filter
- Snowball Token Filter
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- Parsing synonym files
- 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
- Exclude mode settings example
- Classic Token Filter
- Apostrophe Token Filter
- Decimal Digit Token Filter
- Fingerprint Token Filter
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- Remove Duplicates Token Filter
- Character Filters
- Modules
- Index modules
- Ingest node
- Pipeline Definition
- Ingest APIs
- Accessing Data in Pipelines
- Conditional Execution in Pipelines
- Handling Failures in Pipelines
- Processors
- Append Processor
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- Date Processor
- Date Index Name Processor
- Dissect Processor
- Dot Expander Processor
- Drop Processor
- Fail Processor
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- GeoIP Processor
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- Gsub Processor
- HTML Strip Processor
- Join Processor
- JSON Processor
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- Pipeline Processor
- Remove Processor
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- Script Processor
- Set Processor
- Set Security User Processor
- Split Processor
- Sort Processor
- Trim Processor
- Uppercase Processor
- URL Decode Processor
- User Agent processor
- Managing the index lifecycle
- Getting started with index lifecycle management
- Policy phases and actions
- Set up index lifecycle management policy
- Using policies to manage index rollover
- Update policy
- Index lifecycle error handling
- Restoring snapshots of managed indices
- Start and stop index lifecycle management
- Using ILM with existing indices
- SQL access
- Overview
- Getting Started with SQL
- Conventions and Terminology
- Security
- SQL REST API
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- SQL CLI
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- Functions and Operators
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- LIKE and RLIKE Operators
- Aggregate Functions
- Grouping Functions
- Date/Time and Interval Functions and Operators
- Full-Text Search Functions
- Mathematical Functions
- String Functions
- Type Conversion Functions
- Geo Functions
- Conditional Functions And Expressions
- System Functions
- Reserved keywords
- SQL Limitations
- Monitor a cluster
- Frozen indices
- Set up a cluster for high availability
- Roll up or transform your data
- X-Pack APIs
- Info API
- Cross-cluster replication APIs
- Explore API
- Freeze index
- Index lifecycle management API
- Licensing APIs
- Machine learning APIs
- Add events to calendar
- Add jobs to calendar
- Close jobs
- Create jobs
- Create calendar
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- Create filter
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- Revert model snapshots
- Set upgrade mode
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- Stop datafeeds
- Update datafeeds
- Update filter
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- Update model snapshots
- Migration APIs
- Rollup APIs
- Security APIs
- Authenticate
- Change passwords
- Clear cache
- Clear roles cache
- Create API keys
- Create or update application privileges
- Create or update role mappings
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- Create or update users
- Delete application privileges
- Delete role mappings
- Delete roles
- Delete users
- Disable users
- Enable users
- Get API key information
- Get application privileges
- Get role mappings
- Get roles
- Get token
- Get users
- Has privileges
- Invalidate API key
- Invalidate token
- OpenID Connect Prepare Authentication API
- OpenID Connect Authenticate API
- OpenID Connect Logout API
- SSL certificate
- Transform APIs
- Unfreeze index
- Watcher APIs
- Definitions
- 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
- Configuring a Kerberos realm
- Security files
- FIPS 140-2
- How security works
- User authentication
- Built-in users
- Internal users
- Token-based authentication services
- Realms
- Realm chains
- Active Directory user authentication
- File-based user authentication
- LDAP user authentication
- Native user authentication
- OpenID Connect authentication
- PKI user authentication
- SAML authentication
- Kerberos authentication
- Integrating with other authentication systems
- Enabling anonymous access
- Controlling the user cache
- Configuring SAML single-sign-on on the Elastic Stack
- Configuring single sign-on to the Elastic Stack using OpenID Connect
- User authorization
- Auditing security events
- Encrypting communications
- Restricting connections with IP filtering
- Cross cluster search, clients, and integrations
- Tutorial: Getting started with security
- Tutorial: Encrypting communications
- Troubleshooting
- 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 Kerberos 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
- Command line tools
- How To
- Testing
- Glossary of terms
- Release highlights
- Breaking changes
- Release notes
- Elasticsearch version 7.2.1
- Elasticsearch version 7.2.0
- Elasticsearch version 7.1.1
- Elasticsearch version 7.1.0
- Elasticsearch version 7.0.0
- Elasticsearch version 7.0.0-rc2
- Elasticsearch version 7.0.0-rc1
- Elasticsearch version 7.0.0-beta1
- Elasticsearch version 7.0.0-alpha2
- Elasticsearch version 7.0.0-alpha1
Adding and removing nodes
editAdding and removing nodes
editAs nodes are added or removed Elasticsearch maintains an optimal level of fault tolerance by automatically updating the cluster’s voting configuration, which is the set of master-eligible nodes whose responses are counted when making decisions such as electing a new master or committing a new cluster state.
It is recommended to have a small and fixed number of master-eligible nodes in a cluster, and to scale the cluster up and down by adding and removing master-ineligible nodes only. However there are situations in which it may be desirable to add or remove some master-eligible nodes to or from a cluster.
Adding master-eligible nodes
editIf you wish to add some nodes to your cluster, simply configure the new nodes to find the existing cluster and start them up. Elasticsearch adds the new nodes to the voting configuration if it is appropriate to do so.
During master election or when joining an existing formed cluster, a node
sends a join request to the master in order to be officially added to the
cluster. You can use the cluster.join.timeout
setting to configure how long a
node waits after sending a request to join a cluster. Its default value is 30s
.
See Discovery and cluster formation settings.
Removing master-eligible nodes
editWhen removing master-eligible nodes, it is important not to remove too many all at the same time. For instance, if there are currently seven master-eligible nodes and you wish to reduce this to three, it is not possible simply to stop four of the nodes at once: to do so would leave only three nodes remaining, which is less than half of the voting configuration, which means the cluster cannot take any further actions.
More precisely, if you shut down half or more of the master-eligible nodes all at the same time then the cluster will normally become unavailable. If this happens then you can bring the cluster back online by starting the removed nodes again.
As long as there are at least three master-eligible nodes in the cluster, as a general rule it is best to remove nodes one-at-a-time, allowing enough time for the cluster to automatically adjust the voting configuration and adapt the fault tolerance level to the new set of nodes.
If there are only two master-eligible nodes remaining then neither node can be safely removed since both are required to reliably make progress. To remove one of these nodes you must first inform Elasticsearch that it should not be part of the voting configuration, and that the voting power should instead be given to the other node. You can then take the excluded node offline without preventing the other node from making progress. A node which is added to a voting configuration exclusion list still works normally, but Elasticsearch tries to remove it from the voting configuration so its vote is no longer required. Importantly, Elasticsearch will never automatically move a node on the voting exclusions list back into the voting configuration. Once an excluded node has been successfully auto-reconfigured out of the voting configuration, it is safe to shut it down without affecting the cluster’s master-level availability. A node can be added to the voting configuration exclusion list using the Voting Configuration Exclusions API. For example:
# Add node to voting configuration exclusions list and wait for the system # to auto-reconfigure the node out of the voting configuration up to the # default timeout of 30 seconds POST /_cluster/voting_config_exclusions/node_name # Add node to voting configuration exclusions list and wait for # auto-reconfiguration up to one minute POST /_cluster/voting_config_exclusions/node_name?timeout=1m
The node that should be added to the exclusions list is specified using
node filters in place of node_name
here. If a call to the
voting configuration exclusions API fails, you can safely retry it. Only a
successful response guarantees that the node has actually been removed from the
voting configuration and will not be reinstated. If it’s the active master that
was removed from the voting configuration, then it will abdicate to another
master-eligible node that’s still in the voting configuration, if such a node
is available.
Although the voting configuration exclusions API is most useful for down-scaling a two-node to a one-node cluster, it is also possible to use it to remove multiple master-eligible nodes all at the same time. Adding multiple nodes to the exclusions list has the system try to auto-reconfigure all of these nodes out of the voting configuration, allowing them to be safely shut down while keeping the cluster available. In the example described above, shrinking a seven-master-node cluster down to only have three master nodes, you could add four nodes to the exclusions list, wait for confirmation, and then shut them down simultaneously.
Voting exclusions are only required when removing at least half of the master-eligible nodes from a cluster in a short time period. They are not required when removing master-ineligible nodes, nor are they required when removing fewer than half of the master-eligible nodes.
Adding an exclusion for a node creates an entry for that node in the voting configuration exclusions list, which has the system automatically try to reconfigure the voting configuration to remove that node and prevents it from returning to the voting configuration once it has removed. The current list of exclusions is stored in the cluster state and can be inspected as follows:
GET /_cluster/state?filter_path=metadata.cluster_coordination.voting_config_exclusions
This list is limited in size by the cluster.max_voting_config_exclusions
setting, which defaults to 10
. See Discovery and cluster formation settings. Since
voting configuration exclusions are persistent and limited in number, they must
be cleaned up. Normally an exclusion is added when performing some maintenance
on the cluster, and the exclusions should be cleaned up when the maintenance is
complete. Clusters should have no voting configuration exclusions in normal
operation.
If a node is excluded from the voting configuration because it is to be shut down permanently, its exclusion can be removed after it is shut down and removed from the cluster. Exclusions can also be cleared if they were created in error or were only required temporarily:
# Wait for all the nodes with voting configuration exclusions to be removed from # the cluster and then remove all the exclusions, allowing any node to return to # the voting configuration in the future. DELETE /_cluster/voting_config_exclusions # Immediately remove all the voting configuration exclusions, allowing any node # to return to the voting configuration in the future. DELETE /_cluster/voting_config_exclusions?wait_for_removal=false