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 totrue
the statement will show up insys.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" = $$ended - started > '5 minutes'::interval$$;
- 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 theStatementLog
logger with theINFO
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 settings stats.operations_log_size and stats.operations_log_expiration are disabled, no job information will be collected.
- stats.service.interval
- Default:
24h
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
bigint
ordouble precision
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.
- stats.service.max_bytes_per_sec
- Default:
40mb
Runtime:yes
Specifies the maximum number of bytes per second that can be read on data nodes to collect statistics. If this is set to a positive number, the underlying I/O operations of the ANALYZE statement are throttled.
If the value provided is
0
then the throttling is disabled.
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
bigint
ordouble precision
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
bigint
ordouble precision
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.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
bigint
ordouble precision
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¶
Data sharding and work splitting are at the core of CrateDB. This is how we manage to execute very fast queries over incredibly large datasets. In order for multiple CrateDB nodes to work together a cluster needs to be formed. The process of finding other nodes with which to form a cluster is called discovery. Discovery runs when a CrateDB node starts and when a node is not able to reach the master node and continues until a master node is found or a new master node is elected.
- discovery.seed_hosts
- Default:
127.0.0.1
Runtime:no
In order to form a cluster with CrateDB instances running on other nodes a list of seed master-eligible nodes needs to be provided. This setting should normally contain the addresses of all the master-eligible nodes in the cluster. In order to seed the discovery process the nodes listed here must be live and contactable. This setting contains either an array of hosts or a comma-delimited string. By default a node will bind to the available loopback and scan for local ports between
4300
and4400
to try to connect to other nodes running on the same server. This default behaviour provides local auto clustering without any configuration. Each value should be in the form of host:port or host (where port defaults to the settingtransport.tcp.port
).
Note
IPv6 hosts must be bracketed.
- cluster.initial_master_nodes
- Default:
not set
Runtime:no
Contains a list of node names, full-qualified hostnames or IP addresses of the master-eligible nodes which will vote in the very first election of a cluster that’s bootstrapping for the first time. By default this is not set, meaning it expects this node to join an already formed cluster. In development mode, with no discovery settings configured, this step is performed by the nodes themselves, but this auto-bootstrapping is designed to aim development and is not safe for production. In production you must explicitly list the names or IP addresses of the master-eligible nodes whose votes should be counted in the very first election.
- discovery.type
- Default:
zen
Runtime:no
Allowed values:zen | single-node
Specifies whether CrateDB should form a multiple-node cluster. By default, CrateDB discovers other nodes when forming a cluster and allows other nodes to join the cluster later. If
discovery.type
is set tosingle-node
, CrateDB forms a single-node cluster and the node won’t join any other clusters. This can be useful for testing. It is not recommend to use this for production setups. Thesingle-node
mode also skips bootstrap checks.
Caution
If a node is started without any initial_master_nodes or a discovery_type
set to single-node
(e.g., the default configuration), it will never join
a cluster even if the configuration is subsequently changed.
It is possible to force the node to forget its current cluster state by using the crate-node CLI tool. However, be aware that this may result in data loss.
Unicast host discovery¶
As described above, CrateDB has built-in support for statically specifying a list of addresses that will act as the seed nodes in the discovery process using the discovery.seed_hosts setting.
CrateDB also has support for several different mechanisms of seed nodes discovery. Currently there are two other discovery types: via DNS and via EC2 API.
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.seed_providers
- Default:
not set
Runtime:no
Allowed values:srv
,ec2
See also: Discovery.
Discovery via DNS¶
Crate has built-in support for discovery via DNS. To enable DNS discovery the
discovery.seed_providers
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.seed_providers
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
- Default:
true
Runtime:no
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
- Default:
private_ip
Runtime:no
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 valuedev
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.
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 toall
after starting the last updated node.
Note
This allocation setting has no effect on the recovery of primary shards! Even when
cluster.routing.allocation.enable
is set to none
, nodes will recover
their unassigned local primary shards immediately after restart.
- cluster.routing.rebalance.enable
- Default:
all
Runtime:yes
Allowed values:all | none | primaries | replicas
Enables or 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
Defines when rebalancing will happen based on the total state of all the indices shards in the cluster.
Defaults to
indices_all_active
to reduce chatter during initial recovery.
- cluster.routing.allocation.cluster_concurrent_rebalance
- Default:
2
Runtime:yes
Defines how many concurrent rebalancing tasks are allowed across all nodes.
- cluster.routing.allocation.node_initial_primaries_recoveries
- Default:
4
Runtime:yes
Defines how many concurrent primary shard recoveries are allowed on a node.
Since primary recoveries use data that is already on disk (as opposed to inter-node recoveries), recovery should be fast and so this setting can be higher than node_concurrent_recoveries.
- cluster.routing.allocation.node_concurrent_recoveries
- Default:
2
Runtime:yes
Defines how many concurrent recoveries are allowed on a node.
Attribute-based shard allocation¶
You can control how shards are allocated to specific nodes by setting custom attributes on each node (e.g., server rack ID or node availability zone). After doing this, you can define cluster-wide attribute awareness and then configure cluster-wide attribute filtering.
See also
For an in-depth example of using custom node attributes, check out the multi-zone setup how-to guide.
Cluster-wide attribute awareness¶
To make use of custom attributes for attribute-based shard allocation, you must configure cluster-wide attribute awareness.
- cluster.routing.allocation.awareness.attributes
- Runtime:
no
You may define custom node attributes which can then be used to do awareness based on the allocation of a shard and its replicas.
For example, let’s say we want to use an attribute named
rack_id
. We start two nodes withnode.attr.rack_id
set torack_one
. Then we create a single table with five shards and one replica. The table will be fully deployed on the current nodes (five shards and one replica each, making a total of 10 shards).Now, if we start two more nodes with
node.attr.rack_id
set torack_two
, CrateDB will relocate shards to even out the number of shards across the nodes. However, a shard and its replica will not be allocated to nodes sharing the samerack_id
value.The
awareness.attributes
setting supports using several values.
- cluster.routing.allocation.awareness.force.*.values
- Runtime:
no
Attributes on which shard allocation will be forced. Here,
*
is a placeholder for the awareness attribute, which can be configured using the cluster.routing.allocation.awareness.attributes setting.For example, let’s say we configured forced shard allocation for an awareness attribute named
zone
withvalues
set tozone1, zone2
. Start two nodes withnode.attr.zone
set tozone1
. Then, create a table with five shards and one replica. The table will be created, but only five shards will be allocated (with no replicas). The replicas will only be allocated when we start one or more nodes withnode.attr.zone
set tozone2
.
Cluster-wide attribute filtering¶
To control how CrateDB uses custom attributes for attribute-based shard allocation, you must configure cluster-wide attribute filtering.
Note
CrateDB will retroactively enforce filter definitions. If a new filter would prevent newly created matching shards from being allocated to a node, CrateDB would also move any existing matching shards away from that node.
- cluster.routing.allocation.include.*
- Runtime:
yes
Only allocate shards on nodes where at least one of the specified values matches the attribute.
For example:
cluster.routing.allocation.include.zone: "zone1,zone2"`
- cluster.routing.allocation.exclude.*
- Runtime:
yes
Only allocate shards on nodes where none of the specified values matches the attribute.
For example:
cluster.routing.allocation.exclude.zone: "zone1"
- cluster.routing.allocation.require.*
- Runtime:
yes
Used to specify a number of rules, which all of them must match for a node in order to allocate a shard on it.
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
blocks.read_only_allow_delete setting is automatically reset to
FALSE
for the tables if the disk space is freed and the threshold is undershot.
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.
Note
The watermark settings are also used for the Routing allocation disk watermark low and Routing allocation disk watermark high node check.
Setting cluster.routing.allocation.disk.threshold_enabled
to false will
disable the allocation decider, but the node checks will still be active and
warn users about running low on disk space.
- cluster.routing.allocation.total_shards_per_node
- Default:
-1
Runtime:yes
Limits the number of primary and replica shards that can be allocated per node. A value of
-1
means unlimited.Setting this to
1000
, for example, will prevent CrateDB from assigning more than 1000 shards per node. A node with 1000 shards would be excluded from allocation decisions and CrateDB would attempt to allocate shards to other nodes, or leave shards unassigned if no suitable node can be found.
Note
If a table is created with number_of_replicas
provided as a range or default 0-1
value, the limit check accounts only
for primary shards and not for possible expanded replicas and thus actual
number of all shards can exceed the limit.
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.
- indices.recovery.max_concurrent_file_chunks
- Default:
2
Runtime:yes
Controls the number of file chunk requests that can be sent in parallel per recovery. As multiple recoveries are already running in parallel, controlled by cluster.routing.allocation.node_concurrent_recoveries, increasing this expert-level setting might only help in situations where peer recovery of a single shard is not reaching the total inbound and outbound peer recovery traffic as configured by indices.recovery.max_bytes_per_sec, but is CPU-bound instead, typically when using transport-level security or compression.
Memory management¶
- memory.allocation.type
- Default:
on-heap
Runtime:yes
Supported values are on-heap
and off-heap
. This influences if memory is
preferably allocated in the heap space or in the off-heap/direct memory region.
Setting this to off-heap
doesn’t imply that the heap won’t be used anymore.
Most allocations will still happen in the heap space but some operations will
be allowed to utilize off heap buffers.
Warning
Using off-heap
is considered experimental.
- memory.operation_limit
- Default:
0
Runtime:yes
Default value for the memory.operation_limit session setting. Changing the cluster setting will only affect new sessions, not existing sessions.
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 (like
1mb
) or percentage of the heap size (like12%
). A value of-1
disables breaking the circuit while still accounting memory usage.
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.
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
Caution
This setting is deprecated and will be removed in a future release.
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.
Total circuit breaker¶
- indices.breaker.total.limit
- Default:
95%
Runtime:yes
The maximum memory that can be used by all aforementioned circuit breakers together.
Even if an individual circuit breaker doesn’t hit its individual limit, queries might still get aborted if several circuit breakers together would hit the memory limit configured in
indices.breaker.total.limit
.
Thread pools¶
Every node uses a number of thread pools to schedule operations, each pool is dedicated to specific operations. The most important pools are:
write
: Used for write operations like index, update or delete. Thetype
defaults tofixed
.search
: Used for read operations likeSELECT
statements. Thetype
defaults tofixed
.get
: Used for some specific read operations. For example on tables likesys.shards
orsys.nodes
. Thetype
defaults tofixed
.refresh
: Used for refresh operations. Thetype
defaults toscaling
.generic
: For internal tasks like cluster state management. Thetype
defaults toscaling
.logical_replication
: For logical replication operations. Thetype
defaults to fixed.
In addition to those pools, there are also netty
worker threads which are
used to process network requests and many CPU bound actions like query analysis
and optimization.
The thread pool settings are expert settings which you generally shouldn’t need to touch. They are dynamically sized depending on the number of available CPU cores. If you’re running multiple services on the same machine you instead should change the processors setting.
Increasing the number of threads for a pool can result in degraded performance due to increased context switching and higher memory footprint.
If you observe idle CPU cores increasing the thread pool size is rarely the right course of action, instead it can be a sign that:
Operations are blocked on disk IO. Increasing the thread pool size could result in more operations getting queued and blocked on disk IO without increasing throughput but decreasing it due to more memory pressure and additional garbage collection activity.
Individual operations running single threaded. Not all tasks required to process a SQL statement can be further subdivided and processed in parallel, but many operations default to use one thread per shard. Because of this, you can consider increasing the number of shards of a table to increase the parallelism of a single individual statement and increase CPU core utilization. As an alternative you can try increasing the concurrency on the client side, to have CrateDB process more SQL statements in parallel.
- 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 write:
200
Default search:1000
Default get:100
Runtime:no
Size of the queue for pending requests. A value of
-1
sets it to unbounded. If you have burst workloads followed by periods of inactivity it can make sense to increase thequeue_size
to allow a node to buffer more queries before rejecting new operations. But be aware, increasing the queue size if you have sustained workloads will only increase the system’s memory consumption and likely degrade performance.
Overload Protection¶
Overload protection settings control how many resources operations like
INSERT INTO FROM QUERY
or COPY
can use.
The values here serve as a starting point for an algorithm that dynamically adapts the effective concurrency limit based on the round-trip time of requests. Whenever one of these settings is updated, the previously calculated effective concurrency is reset.
Changing settings will only effect new operations, already running operations will continue with the previous settings.
- overload_protection.dml.initial_concurrency
- Default:
5
Runtime:yes
The initial number of concurrent operations allowed per target node.
- overload_protection.dml.min_concurrency
- Default:
1
Runtime:yes
The minimum number of concurrent operations allowed per target node.
- overload_protection.dml.max_concurrency
- Default:
2000
Runtime:yes
The maximum number of concurrent operations allowed per target node.
- overload_protection.dml.queue_size
- Default:
200
Runtime:yes
How many operations are allowed to queue up.
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 following settings can be used to configure the behavior of the metadata gateway.
- gateway.expected_nodes
- Default:
-1
Runtime:no
The setting
gateway.expected_nodes
defines the total number of nodes expected in the cluster. It is evaluated together withgateway.recover_after_nodes
to decide if the cluster can start with recovery.Caution
This setting is deprecated and will be removed in a future version. Use gateway.expected_data_nodes instead.
- gateway.expected_data_nodes
- Default:
-1
Runtime:no
The setting
gateway.expected_data_nodes
defines the total number of data nodes expected in the cluster. It is evaluated together withgateway.recover_after_data_nodes
to decide if the cluster can start with recovery.
- gateway.recover_after_time
- Default:
5m
Runtime:no
The
gateway.recover_after_time
setting defines the time to wait for the number of nodes set ingateway.expected_data_nodes
(orgateway.expected_nodes
) to become available, before starting the recovery, once the number of nodes defined ingateway.recover_after_data_nodes
(orgateway.recover_after_nodes
) has already been reached. This setting is ignored ifgateway.expected_data_nodes
orgateway.expected_nodes
are set to 0 or 1. It also has no effect ifgateway.recover_after_data_nodes
is set equal togateway.expected_data_nodes
(orgateway.recover_after_nodes
is set equal togateway.expected_nodes
). The cluster also proceeds to immediate recovery, and the default 5 minutes waiting time does not apply, if neither this setting norexpected_nodes
andexpected_data_nodes
are explicitly set.
- gateway.recover_after_nodes
- Default:
-1
Runtime:no
The
gateway.recover_after_nodes
setting defines the number of nodes that need to join the cluster before the cluster state recovery can start. If this setting is-1
andgateway.expected_nodes
is set, all nodes will need to be started before the cluster state recovery can start. Please note that proceeding with recovery when not all nodes are available could trigger the promotion of shards and the creation of new replicas, generating disk and network load, which may be unnecessary. You can use a combination of this setting withgateway.recovery_after_time
to mitigate this risk.Caution
This setting is deprecated and will be removed in CrateDB 5.0. Use gateway.recover_after_data_nodes instead.
- gateway.recover_after_data_nodes
- Default:
-1
Runtime:no
The
gateway.recover_after_data_nodes
setting defines the number of data nodes that need to be started before the cluster state recovery can start. If this setting is-1
andgateway.expected_data_nodes
is set, all data nodes will need to be started before the cluster state recovery can start. Please note that proceeding with recovery when not all data nodes are available could trigger the promotion of shards and the creation of new replicas, generating disk and network load, which may be unnecessary. You can use a combination of this setting withgateway.recovery_after_time
to mitigate this risk.
Logical Replication¶
Replication process can be configured by the following settings. Settings are dynamic and can be changed in runtime.
- replication.logical.ops_batch_size
- Default:
50000
Min value:16
Runtime:yes
Maximum number of operations to replicate from the publisher cluster per poll. Represents a number to advance a sequence.
- replication.logical.reads_poll_duration
- Default:
50
Runtime:yes
The maximum time (in milliseconds) to wait for changes per poll operation. When
a subscriber makes another one request to a publisher, it has
reads_poll_duration
milliseconds to harvest changes from the publisher.
- replication.logical.recovery.chunk_size
- Default:
1MB
Min value:1KB
Max value:1GB
Runtime:yes
Chunk size to transfer files during the initial recovery of a replicating table.
- replication.logical.recovery.max_concurrent_file_chunks
- Default:
2
Min value:1
Max value:5
Runtime:yes
Controls the number of file chunk requests that can be sent in parallel between clusters during the recovery.