druid/docs/content/configuration/broker.md

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Broker Node Configuration

For general Broker Node information, see here.

Runtime Configuration

The broker node uses several of the global configs in Configuration and has the following set of configurations as well:

Node Configs

Property	Description	Default
druid.host	The host for the current node. This is used to advertise the current processes location as reachable from another node and should generally be specified such that http://${druid.host}/ could actually talk to this process	InetAddress.getLocalHost().getCanonicalHostName()
druid.port	This is the port to actually listen on; unless port mapping is used, this will be the same port as is on druid.host	8082
druid.service	The name of the service. This is used as a dimension when emitting metrics and alerts to differentiate between the various services	druid/broker

Query Configs

Query Prioritization

Property	Possible Values	Description	Default
druid.broker.balancer.type	random, connectionCount	Determines how the broker balances connections to historical nodes. random choose randomly, connectionCount picks the node with the fewest number of active connections to	random
druid.broker.select.tier	highestPriority, lowestPriority, custom	If segments are cross-replicated across tiers in a cluster, you can tell the broker to prefer to select segments in a tier with a certain priority.	highestPriority
druid.broker.select.tier.custom.priorities	An array of integer priorities.	Select servers in tiers with a custom priority list.	None

Concurrent Requests

Druid uses Jetty to serve HTTP requests.

Property	Description	Default
druid.server.http.numThreads	Number of threads for HTTP requests.	10
druid.server.http.maxIdleTime	The Jetty max idle time for a connection.	PT5m
druid.broker.http.numConnections	Size of connection pool for the Broker to connect to historical and real-time nodes. If there are more queries than this number that all need to speak to the same node, then they will queue up.	5
druid.broker.http.readTimeout	The timeout for data reads.	PT15M

Retry Policy

Druid broker can optionally retry queries internally for transient errors.

Property	Description	Default
druid.broker.retryPolicy.numTries	Number of tries.	1

Processing

The broker uses processing configs for nested groupBy queries. And, optionally, Long-interval queries (of any type) can be broken into shorter interval queries and processed in parallel inside this thread pool. For more details, see "chunkPeriod" in Query Context doc.

Property	Description	Default
druid.processing.buffer.sizeBytes	This specifies a buffer size for the storage of intermediate results. The computation engine in both the Historical and Realtime nodes will use a scratch buffer of this size to do all of their intermediate computations off-heap. Larger values allow for more aggregations in a single pass over the data while smaller values can require more passes depending on the query that is being executed.	1073741824 (1GB)
druid.processing.buffer.poolCacheMaxCount	processing buffer pool caches the buffers for later use, this is the maximum count cache will grow to. note that pool can create more buffers than it can cache if necessary.	Integer.MAX_VALUE
druid.processing.formatString	Realtime and historical nodes use this format string to name their processing threads.	processing-%s
druid.processing.numThreads	The number of processing threads to have available for parallel processing of segments. Our rule of thumb is num_cores - 1, which means that even under heavy load there will still be one core available to do background tasks like talking with ZooKeeper and pulling down segments. If only one core is available, this property defaults to the value 1.	Number of cores - 1 (or 1)
druid.processing.columnCache.sizeBytes	Maximum size in bytes for the dimension value lookup cache. Any value greater than 0 enables the cache. It is currently disabled by default. Enabling the lookup cache can significantly improve the performance of aggregators operating on dimension values, such as the JavaScript aggregator, or cardinality aggregator, but can slow things down if the cache hit rate is low (i.e. dimensions with few repeating values). Enabling it may also require additional garbage collection tuning to avoid long GC pauses.	0 (disabled)
druid.processing.fifo	If the processing queue should treat tasks of equal priority in a FIFO manner	false

General Query Configuration

GroupBy Query Config

Property	Description	Default
druid.query.groupBy.singleThreaded	Run single threaded group By queries.	false
druid.query.groupBy.maxIntermediateRows	Maximum number of intermediate rows.	50000
druid.query.groupBy.maxResults	Maximum number of results.	500000

Search Query Config

Property	Description	Default
druid.query.search.maxSearchLimit	Maximum number of search results to return.	1000

Segment Metadata Query Config

Property	Description	Default
druid.query.segmentMetadata.defaultHistory	When no interval is specified in the query, use a default interval of defaultHistory before the end time of the most recent segment, specified in ISO8601 format. This property also controls the duration of the default interval used by GET /druid/v2/datasources/{dataSourceName} interactions for retrieving datasource dimensions/metrics.	P1W

Caching

You can optionally only configure caching to be enabled on the broker by setting caching configs here.

Property	Possible Values	Description	Default
druid.broker.cache.useCache	true, false	Enable the cache on the broker.	false
druid.broker.cache.populateCache	true, false	Populate the cache on the broker.	false
druid.broker.cache.unCacheable	All druid query types	All query types to not cache.	["groupBy", "select"]
druid.broker.cache.cacheBulkMergeLimit	positive integer or 0	Queries with more segments than this number will not attempt to fetch from cache at the broker level, leaving potential caching fetches (and cache result merging) to the historicals	Integer.MAX_VALUE

See cache configuration for how to configure cache settings.