Cluster Wide Settings

All current applied cluster settings can be read by querying the sys.cluster.settings column. Most cluster settings can be changed at runtime. This is documented at each setting.

Table of Contents

Non-Runtime Cluster Wide Settings

Cluster wide settings which cannot be changed at runtime need to be specified in the configuration of each node in the cluster.

Caution

Cluster settings specified via node configurations are required to be exactly the same on every node in the cluster for proper operation of the cluster.

Collecting Stats

stats.enabled
Default: true
Runtime: yes

A boolean indicating whether or not to collect statistical information about the cluster.

Caution

The collection of statistical information incurs a slight performance penalty, as details about every job and operation across the cluster will cause data to be inserted into the corresponding system tables.

stats.jobs_log_size
Default: 10000
Runtime: yes

The maximum number of job records kept to be kept in the sys.jobs_log table on each node.

A job record corresponds to a single SQL statement to be executed on the cluster. These records are used for performance analytics. A larger job log produces more comprehensive stats, but uses more RAM.

Older job records are deleted as newer records are added, once the limit is reached.

Setting this value to 0 disables collecting job information.

stats.jobs_log_expiration
Default: 0s (disabled)
Runtime: yes

The job record expiry time in seconds.

Job records in the sys.jobs_log table are periodically cleared if they are older than the expiry time. This setting overrides stats.jobs_log_size.

If the value is set to 0, time based log entry eviction is disabled.

Note

If both the stats.operations_log_size and stats.operations_log_expiration settings are disabled, jobs will not be recorded.

stats.jobs_log_filter
Default: true (Include everything)
Runtime: yes

An expression to determine if a job should be recorded into sys.jobs_log. The expression must evaluate to a boolean. If it evaluates to true the statement will show up sys.jobs_log until it’s evicted due to one of the other rules. (expiration or size limit reached).

The expression may reference all columns contained in sys.jobs_log. A common use case is to include only jobs that took a certain amount of time to execute:

cr> SET GLOBAL "stats.jobs_log_filter" = 'ended - started > 100';
stats.jobs_log_persistent_filter
Default: false (Include nothing)
Runtime: yes

An expression to determine if a job should also be recorded to the regular CrateDB log. Entries that match this filter will be logged under the StatementLog logger with the INFO level.

This is similar to stats.jobs_log_filter except that these entries are persisted to the log file. This should be used with caution and shouldn’t be set to an expression that matches many queries as the logging operation will block on IO and can therefore affect performance.

A common use case is to use this for slow query logging.

stats.operations_log_size
Default: 10000
Runtime: yes

The maximum number of operations records to be kept in the sys.operations_log table on each node.

A job consists of one or more individual operations. Operations records are used for performance analytics. A larger operations log produces more comprehensive stats, but uses more RAM.

Older operations records are deleted as newer records are added, once the limit is reached.

Setting this value to 0 disables collecting operations information.

stats.operations_log_expiration
Default: 0s (disabled)
Runtime: yes

Entries of sys.operations_log are cleared by a periodically job when they are older than the specified expire time. This setting overrides stats.operations_log_size. If the value is set to 0 the time based log entry eviction is disabled.

Note

If both setttings stats.operations_log_size and stats.operations_log_expiration are disabled, no job information will be collected.

stats.service.interval
Default: 1h
Runtime: yes

Defines the refresh interval to refresh tables statistics used to produce optimal query execution plans.

This field expects a time value either as a long or double or alternatively as a string literal with a time suffix (ms, s, m, h, d, w).

If the value provided is 0 then the refresh is disabled.

Caution

Using a very small value can cause a high load on the cluster.

Usage Data Collector

The settings of the Usage Data Collector are read-only and cannot be set during runtime. Please refer to Usage Data Collector to get further information about its usage.

udc.enabled
Default: true
Runtime: no

true: Enables the Usage Data Collector.

false: Disables the Usage Data Collector.

udc.initial_delay
Default: 10m
Runtime: no

The delay for first ping after start-up.

This field expects a time value either as a long or double or alternatively as a string literal with a time suffix (ms, s, m, h, d, w).

udc.interval
Default: 24h
Runtime: no

The interval a UDC ping is sent.

This field expects a time value either as a long or double or alternatively as a string literal with a time suffix (ms, s, m, h, d, w).

udc.url
Default: https://udc.crate.io
Runtime: no

The URL the ping is sent to.

Graceful Stop

By default, when the CrateDB process stops it simply shuts down, possibly making some shards unavailable which leads to a red cluster state and lets some queries fail that required the now unavailable shards. In order to safely shutdown a CrateDB node, the graceful stop procedure can be used.

The following cluster settings can be used to change the shutdown behaviour of nodes of the cluster:

cluster.graceful_stop.min_availability
Default: primaries
Runtime: yes
Allowed Values: none | primaries | full

none: No minimum data availability is required. The node may shut down even if records are missing after shutdown.

primaries: At least all primary shards need to be available after the node has shut down. Replicas may be missing.

full: All records and all replicas need to be available after the node has shut down. Data availability is full.

Note

This option is ignored if there is only 1 node in a cluster!

cluster.graceful_stop.reallocate
Default: true
Runtime: yes

true: The graceful stop command allows shards to be reallocated before shutting down the node in order to ensure minimum data availability set with min_availability.

false: The graceful stop command will fail if the cluster would need to reallocate shards in order to ensure the minimum data availability set with min_availability.

Warning

Make sure you have enough nodes and enough disk space for the reallocation.

cluster.graceful_stop.timeout
Default: 2h
Runtime: yes

Defines the maximum waiting time in milliseconds for the reallocation process to finish. The force setting will define the behaviour when the shutdown process runs into this timeout.

The timeout expects a time value either as a long or double or alternatively as a string literal with a time suffix (ms, s, m, h, d, w).

cluster.graceful_stop.force
Default: false
Runtime: yes

Defines whether graceful stop should force stopping of the node if it runs into the timeout which is specified with the cluster.graceful_stop.timeout setting.

Bulk Operations

SQL DML Statements involving a huge amount of rows like COPY FROM, INSERT or UPDATE can take an enormous amount of time and resources. The following settings change the behaviour of those queries.

bulk.request_timeout
Default: 1m
Runtime: yes

Defines the timeout of internal shard-based requests involved in the execution of SQL DML Statements over a huge amount of rows.

Discovery

discovery.zen.minimum_master_nodes
Default: 1
Runtime: yes

Set to ensure a node sees N other master eligible nodes to be considered operational within the cluster. It’s recommended to set it to a higher value than 1 when running more than 2 nodes in the cluster.

discovery.zen.ping_interval
Default: 1s
Runtime: yes

How often to ping other nodes.

Nodes must remain responsive to pings or they will be marked as failed and removed from the cluster.

discovery.zen.ping_timeout
Default: 3s
Runtime: yes

The time to wait for ping responses from other nodes when discovering. Set this option to a higher value on a slow or congested network to minimize discovery failures.

discovery.zen.ping_retries
Default: 3
Runtime: yes

How many ping failures (network timeouts) indicate that a node has failed.

discovery.zen.publish_timeout
Default: 30s
Runtime: yes

Time a node is waiting for responses from other nodes to a published cluster state.

Note

Multicast used to be an option for node discovery, but was deprecated in CrateDB 1.0.3 and removed in CrateDB 1.1.

Unicast Host Discovery

CrateDB has built-in support for several different mechanisms of node discovery. The simplest mechanism is to specify a list of hosts in the configuration file.

discovery.zen.ping.unicast.hosts
Default: not set
Runtime: no

Currently there are three other discovery types: via DNS, via EC2 API and via Microsoft Azure mechanisms.

When a node starts up with one of these discovery types enabled, it performs a lookup using the settings for the specified mechanism listed below. The hosts and ports retrieved from the mechanism will be used to generate a list of unicast hosts for node discovery.

The same lookup is also performed by all nodes in a cluster whenever the master is re-elected (see Cluster Meta Data).

discovery.zen.hosts_provider
Default: not set
Runtime: no
Allowed Values: srv, ec2, azure

See also: Discovery.

Discovery via DNS

Crate has built-in support for discovery via DNS. To enable DNS discovery the discovery.zen.hosts_provider setting needs to be set to srv.

The order of the unicast hosts is defined by the priority, weight and name of each host defined in the SRV record. For example:

_crate._srv.example.com. 3600 IN SRV 2 20 4300 crate1.example.com.
_crate._srv.example.com. 3600 IN SRV 1 10 4300 crate2.example.com.
_crate._srv.example.com. 3600 IN SRV 2 10 4300 crate3.example.com.

would result in a list of discovery nodes ordered like:

crate2.example.com:4300, crate3.example.com:4300, crate1.example.com:4300
discovery.srv.query
Runtime: no

The DNS query that is used to look up SRV records, usually in the format _service._protocol.fqdn If not set, the service discovery will not be able to look up any SRV records.

discovery.srv.resolver
Runtime: no

The hostname or IP of the DNS server used to resolve DNS records. If this is not set, or the specified hostname/IP is not resolvable, the default (system) resolver is used.

Optionally a custom port can be specified using the format hostname:port.

Discovery on Amazon EC2

CrateDB has built-in support for discovery via the EC2 API. To enable EC2 discovery the discovery.zen.hosts_provider settings needs to be set to ec2.

discovery.ec2.access_key
Runtime: no

The access key ID to identify the API calls.

discovery.ec2.secret_key
Runtime: no

The secret key to identify the API calls.

Following settings control the discovery:

discovery.ec2.groups
Runtime: no

A list of security groups; either by ID or name. Only instances with the given group will be used for unicast host discovery.

discovery.ec2.any_group
Runtime: no
Default: true

Defines whether all (false) or just any (true) security group must be present for the instance to be used for discovery.

discovery.ec2.host_type
Runtime: no
Default: private_ip
Allowed Values: private_ip, public_ip, private_dns, public_dns

Defines via which host type to communicate with other instances.

discovery.ec2.availability_zones
Runtime: no

A list of availability zones. Only instances within the given availability zone will be used for unicast host discovery.

discovery.ec2.tag.<name>
Runtime: no

EC2 instances for discovery can also be filtered by tags using the discovery.ec2.tag. prefix plus the tag name.

E.g. to filter instances that have the environment tags with the value dev your setting will look like: discovery.ec2.tag.environment: dev.

discovery.ec2.endpoint
Runtime: no

If you have your own compatible implementation of the EC2 API service you can set the endpoint that should be used.

Discovery on Microsoft Azure

CrateDB has built-in support for discovery via the Azure Virtual Machine API. To enable Azure discovery set the discovery.zen.hosts_provider setting to azure.

cloud.azure.management.resourcegroup.name
Runtime: no

The name of the resource group the CrateDB cluster is running on.

All nodes need to be started within the same resource group.

cloud.azure.management.subscription.id
Runtime: no

The subscription ID of your Azure account.

You can find the ID on the Azure Portal.

cloud.azure.management.tenant.id
Runtime: no

The tenant ID of the Active Directory application.

cloud.azure.management.app.id
Runtime: no

The application ID of the Active Directory application.

cloud.azure.management.app.secret
Runtime: no

The password of the Active Directory application.

discovery.azure.method
Runtime: no
Default: vnet
Allowed Values: vnet | subnet

Defines the scope of the discovery. vnet will discover all VMs within the same virtual network (default), subnet will discover all VMs within the same subnet of the CrateDB instance.

Routing Allocation

cluster.routing.allocation.enable
Default: all
Runtime: yes
Allowed Values: all | none | primaries | new_primaries

all allows all shard allocations, the cluster can allocate all kinds of shards.

none allows no shard allocations at all. No shard will be moved or created.

primaries only primaries can be moved or created. This includes existing primary shards.

new_primaries allows allocations for new primary shards only. This means that for example a newly added node will not allocate any replicas. However it is still possible to allocate new primary shards for new indices. Whenever you want to perform a zero downtime upgrade of your cluster you need to set this value before gracefully stopping the first node and reset it to all after starting the last updated node.

Note

This allocation setting has no effect on recovery of primary shards! Even when cluster.routing.allocation.enable is set to none, nodes will recover their unassigned local primary shards immediatelly after restart.

cluster.routing.rebalance.enable
Default: all
Runtime: yes
Allowed Values: all | none | primaries | replicas

Enables/Disables rebalancing for different types of shards.

all allows shard rebalancing for all types of shards.

none disables shard rebalancing for any types.

primaries allows shard rebalancing only for primary shards.

replicas allows shard rebalancing only for replica shards.

cluster.routing.allocation.allow_rebalance
Default: indices_all_active
Runtime: yes
Allowed Values: always | indices_primary_active | indices_all_active

Allow to control when rebalancing will happen based on the total state of all the indices shards in the cluster. Defaulting to indices_all_active to reduce chatter during initial recovery.

cluster.routing.allocation.cluster_concurrent_rebalance
Default: 2
Runtime: yes

Define how many concurrent rebalancing tasks are allowed cluster wide.

cluster.routing.allocation.node_initial_primaries_recoveries
Default: 4
Runtime: yes

Define the number of initial recoveries of primaries that are allowed per node. Since most times local gateway is used, those should be fast and we can handle more of those per node without creating load.

cluster.routing.allocation.node_concurrent_recoveries
Default: 2
Runtime: yes

How many concurrent recoveries are allowed to happen on a node.

Awareness

Cluster allocation awareness allows to configure shard and replicas allocation across generic attributes associated with nodes.

cluster.routing.allocation.awareness.attributes
Runtime: no

Define node attributes which will be used to do awareness based on the allocation of a shard and its replicas. For example, let’s say we have defined an attribute rack_id and we start 2 nodes with node.attr.rack_id set to rack_one, and deploy a single table with 5 shards and 1 replica. The table will be fully deployed on the current nodes (5 shards and 1 replica each, total of 10 shards).

Now, if we start two more nodes, with node.attr.rack_id set to rack_two, shards will relocate to even the number of shards across the nodes, but a shard and its replica will not be allocated in the same rack_id value.

The awareness attributes can hold several values

cluster.routing.allocation.awareness.force.*.values
Runtime: no

Attributes on which shard allocation will be forced. * is a placeholder for the awareness attribute, which can be defined using the cluster.routing.allocation.awareness.attributes setting. Let’s say we configured an awareness attribute zone and the values zone1, zone2 here, start 2 nodes with node.attr.zone set to zone1 and create a table with 5 shards and 1 replica. The table will be created, but only 5 shards will be allocated (with no replicas). Only when we start more shards with node.attr.zone set to zone2 the replicas will be allocated.

Balanced Shards

All these values are relative to one another. The first three are used to compose a three separate weighting functions into one. The cluster is balanced when no allowed action can bring the weights of each node closer together by more then the fourth setting. Actions might not be allowed, for instance, due to forced awareness or allocation filtering.

cluster.routing.allocation.balance.shard
Default: 0.45f
Runtime: yes

Defines the weight factor for shards allocated on a node (float). Raising this raises the tendency to equalize the number of shards across all nodes in the cluster.

cluster.routing.allocation.balance.index
Default: 0.55f
Runtime: yes

Defines a factor to the number of shards per index allocated on a specific node (float). Increasing this value raises the tendency to equalize the number of shards per index across all nodes in the cluster.

cluster.routing.allocation.balance.threshold
Default: 1.0f
Runtime: yes

Minimal optimization value of operations that should be performed (non negative float). Increasing this value will cause the cluster to be less aggressive about optimising the shard balance.

Cluster-Wide Allocation Filtering

Allow to control the allocation of all shards based on include/exclude filters.

E.g. this could be used to allocate all the new shards on the nodes with specific IP addresses or custom attributes.

cluster.routing.allocation.include.*
Runtime: no

Place new shards only on nodes where one of the specified values matches the attribute. e.g.: cluster.routing.allocation.include.zone: “zone1,zone2”

cluster.routing.allocation.exclude.*
Runtime: no

Place new shards only on nodes where none of the specified values matches the attribute. e.g.: cluster.routing.allocation.exclude.zone: “zone1”

cluster.routing.allocation.require.*
Runtime: no

Used to specify a number of rules, which all MUST match for a node in order to allocate a shard on it. This is in contrast to include which will include a node if ANY rule matches.

Disk-based Shard Allocation

cluster.routing.allocation.disk.threshold_enabled
Default: true
Runtime: yes

Prevent shard allocation on nodes depending of the disk usage.

cluster.routing.allocation.disk.watermark.low
Default: 85%
Runtime: yes

Defines the lower disk threshold limit for shard allocations. New shards will not be allocated on nodes with disk usage greater than this value. It can also be set to an absolute bytes value (like e.g. 500mb) to prevent the cluster from allocating new shards on node with less free disk space than this value.

cluster.routing.allocation.disk.watermark.high
Default: 90%
Runtime: yes

Defines the higher disk threshold limit for shard allocations. The cluster will attempt to relocate existing shards to another node if the disk usage on a node rises above this value. It can also be set to an absolute bytes value (like e.g. 500mb) to relocate shards from nodes with less free disk space than this value.

cluster.routing.allocation.disk.watermark.flood_stage
Default: 95%
Runtime: yes

Defines the threshold on which CrateDB enforces a read-only block on every index that has at least one shard allocated on a node with at least one disk exceeding the flood stage. Note, that the read-only blocks are not automatically removed from the indices if the disk space is freed and the threshold is undershot. To remove the block, execute ALTER TABLE ... SET ("blocks.read_only_allow_delete" = FALSE) for affected tables (see blocks.read_only_allow_delete).

cluster.routing.allocation.disk.watermark settings may be defined as percentages or bytes values. However, it is not possible to mix the value types.

By default, the cluster will retrieve information about the disk usage of the nodes every 30 seconds. This can also be changed by setting the cluster.info.update.interval setting.

Recovery

indices.recovery.max_bytes_per_sec
Default: 40mb
Runtime: yes

Specifies the maximum number of bytes that can be transferred during shard recovery per seconds. Limiting can be disabled by setting it to 0. This setting allows to control the network usage of the recovery process. Higher values may result in higher network utilization, but also faster recovery process.

indices.recovery.retry_delay_state_sync
Default: 500ms
Runtime: yes

Defines the time to wait after an issue caused by cluster state syncing before retrying to recover.

indices.recovery.retry_delay_network
Default: 5s
Runtime: yes

Defines the time to wait after an issue caused by the network before retrying to recover.

indices.recovery.internal_action_timeout
Default: 15m
Runtime: yes

Defines the timeout for internal requests made as part of the recovery.

indices.recovery.internal_action_long_timeout
Default: 30m
Runtime: yes

Defines the timeout for internal requests made as part of the recovery that are expected to take a long time. Defaults to twice internal_action_timeout.

indices.recovery.recovery_activity_timeout
Default: 30m
Runtime: yes

Recoveries that don’t show any activity for more then this interval will fail. Defaults to internal_action_long_timeout.

Query Circuit Breaker

The Query circuit breaker will keep track of the used memory during the execution of a query. If a query consumes too much memory or if the cluster is already near its memory limit it will terminate the query to ensure the cluster keeps working.

indices.breaker.query.limit
Default: 60%
Runtime: yes

Specifies the limit for the query breaker. Provided values can either be absolute values (interpreted as a number of bytes), byte sizes (eg. 1mb) or percentage of the heap size (eg. 12%). A value of -1 disables breaking the circuit while still accounting memory usage.

indices.breaker.query.overhead
Default: 1.09
Runtime: no

A constant that all data estimations are multiplied with to determine a final estimation.

Field Data Circuit Breaker

The field data circuit breaker allows estimation of needed heap memory required for loading field data into memory. If a certain limit is reached an exception is raised.

indices.breaker.fielddata.limit
Default: 60%
Runtime: yes

Specifies the JVM heap limit for the fielddata breaker.

indices.breaker.fielddata.overhead
Default: 1.03
Runtime: yes

A constant that all field data estimations are multiplied with to determine a final estimation.

Request Circuit Breaker

The request circuit breaker allows an estimation of required heap memory per request. If a single request exceeds the specified amount of memory, an exception is raised.

indices.breaker.request.limit
Default: 60%
Runtime: yes

Specifies the JVM heap limit for the request circuit breaker.

indices.breaker.request.overhead
Default: 1.0
Runtime: yes

A constant that all request estimations are multiplied with to determine a final estimation.

Accounting Circuit Breaker

Tracks things that are held in memory independent of queries. For example the memory used by Lucene for segments.

indices.breaker.accounting.limit
Default: 100%
Runtime: yes

Specifies the JVM heap limit for the accounting circuit breaker

indices.breaker.accounting.overhead
Default: 1.0
Runtime: yes

A constant that all accounting estimations are multiplied with to determine a final estimation.

Stats Circuit Breakers

Settings that control the behaviour of the stats circuit breaker. There are two breakers in place, one for the jobs log and one for the operations log. For each of them, the breaker limit can be set.

stats.breaker.log.jobs.limit
Default: 5%
Runtime: yes

The maximum memory that can be used from CRATE_HEAP_SIZE for the sys.jobs_log table on each node.

When this memory limit is reached, the job log circuit breaker logs an error message and clears the sys.jobs_log table completely.

stats.breaker.log.operations.limit
Default: 5%
Runtime: yes

The maximum memory that can be used from CRATE_HEAP_SIZE for the sys.operations_log table on each node.

When this memory limit is reached, the operations log circuit breaker logs an error message and clears the sys.operations_log table completely.

Thread Pools

Every node holds several thread pools to improve how threads are managed within a node. There are several pools, but the important ones include:

  • index: For index/delete operations, defaults to fixed
  • search: For count/search operations, defaults to fixed
  • get: For queries that are optimized to do a direct lookup by primary key, defaults to fixed
  • bulk: For bulk operations, defaults to fixed
  • refresh: For refresh operations, defaults to cache
thread_pool.<name>.type
Runtime: no
Allowed Values: fixed | scaling

fixed holds a fixed size of threads to handle the requests. It also has a queue for pending requests if no threads are available.

scaling ensures that a thread pool holds a dynamic number of threads that are proportional to the workload.

Settings for fixed thread pools

If the type of a thread pool is set to fixed there are a few optional settings.

thread_pool.<name>.size
Runtime: no

Number of threads. The default size of the different thread pools depend on the number of available CPU cores.

thread_pool.<name>.queue_size
Default index: 200
Default search: 1000
Default get: 1000
Default bulk: 50
Runtime: no

Size of the queue for pending requests. A value of -1 sets it to unbounded.

Metadata

cluster.info.update.interval
Default: 30s
Runtime: yes

Defines how often the cluster collect metadata information (e.g. disk usages etc.) if no concrete event is triggered.

Metadata Gateway

The gateway persists cluster meta data on disk every time the meta data changes. This data is stored persistently across full cluster restarts and recovered after nodes are started again.
gateway.expected_nodes
Default: -1
Runtime: no

The setting gateway.expected_nodes defines the number of nodes that should be waited for until the cluster state is recovered immediately. The value of the setting should be equal to the number of nodes in the cluster, because you only want the cluster state to be recovered after all nodes are started.

gateway.recover_after_time
Default: 0ms
Runtime: no

The gateway.recover_after_time setting defines the time to wait before starting starting the recovery once the number of nodes defined in gateway.recover_after_nodes are started. The setting is relevant if gateway.recover_after_nodes is less than gateway.expected_nodes.

gateway.recover_after_nodes
Default: -1
Runtime: no

The gateway.recover_after_nodes setting defines the number of nodes that need to be started before the cluster state recovery will start. Ideally the value of the setting should be equal to the number of nodes in the cluster, because you only want the cluster state to be recovered once all nodes are started. However, the value must be bigger than the half of the expected number of nodes in the cluster.

Credentials for S3 Repositories

CrateDB has built-in support for configuring S3 buckets as repositories for snapshots. If no credentials are provided as parameters to the SQL statement the following default credentials will be used:

s3.client.default.access_key
Runtime: no

The access key ID to identify the API calls.

s3.client.default.secret_key
Runtime: no

The secret key to identify the API calls.

Tip

Configuring the settings above in the crate.yml file, is an easy way to prevent credentials from being exposed.

If a repository is created with the credentials passed as parameters to the SQL statement, then those credentials will be visible as plain text to anyone querying the sys.repositories table.