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.plaintextPort 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.tlsPort TLS port for HTTPS connector, if druid.enableTlsPort is set then this config will be used. If druid.host contains port then that port will be ignored. This should be a non-negative Integer. 8282
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. max(10, (Number of cores * 17) / 16 + 2) + 30
druid.server.http.queueSize Size of the worker queue used by Jetty server to temporarily store incoming client connections. If this value is set and a request is rejected by jetty because queue is full then client would observe request failure with TCP connection being closed immediately with a completely empty response from server. Unbounded
druid.server.http.maxIdleTime The Jetty max idle time for a connection. PT5m
druid.server.http.enableRequestLimit If enabled, no requests would be queued in jetty queue and "HTTP 429 Too Many Requests" error response would be sent. false
druid.server.http.defaultQueryTimeout Query timeout in millis, beyond which unfinished queries will be cancelled 300000
druid.server.http.maxScatterGatherBytes Maximum number of bytes gathered from data nodes such as historicals and realtime processes to execute a query. This is an advance configuration that allows to protect in case broker is under heavy load and not utilizing the data gathered in memory fast enough and leading to OOMs. This limit can be further reduced at query time using maxScatterGatherBytes in the context. Note that having large limit is not necessarily bad if broker is never under heavy concurrent load in which case data gathered is processed quickly and freeing up the memory used. Long.MAX_VALUE
druid.broker.http.numConnections Size of connection pool for the Broker to connect to historical and real-time processes. If there are more queries than this number that all need to speak to the same node, then they will queue up. 20
druid.broker.http.compressionCodec Compression codec the Broker uses to communicate with historical and real-time processes. May be "gzip" or "identity". gzip
druid.broker.http.readTimeout The timeout for data reads from historical and real-time processes. 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.numMergeBuffers The number of direct memory buffers available for merging query results. The buffers are sized by druid.processing.buffer.sizeBytes. This property is effectively a concurrency limit for queries that require merging buffers. If you are using any queries that require merge buffers (currently, just groupBy v2) then you should have at least two of these. max(2, druid.processing.numThreads / 4)
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
druid.processing.tmpDir Path where temporary files created while processing a query should be stored. If specified, this configuration takes priority over the default java.io.tmpdir path. path represented by java.io.tmpdir

The amount of direct memory needed by Druid is at least druid.processing.buffer.sizeBytes * (druid.processing.numMergeBuffers + druid.processing.numThreads + 1). You can ensure at least this amount of direct memory is available by providing -XX:MaxDirectMemorySize=<VALUE> at the command line.

General Query Configuration

GroupBy Query Config

See groupBy server configuration.

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
druid.query.segmentMetadata.defaultAnalysisTypes This can be used to set the Default Analysis Types for all segment metadata queries, this can be overridden when making the query ["cardinality", "interval", "minmax"]

SQL

See SQL server configuration.

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.

Others

Property Possible Values Description Default
druid.broker.segment.watchedTiers List of strings Broker watches the segment announcements from nodes serving segments to build cache of which node is serving which segments, this configuration allows to only consider segments being served from a whitelist of tiers. By default, Broker would consider all tiers. This can be used to partition your dataSources in specific historical tiers and configure brokers in partitions so that they are only queryable for specific dataSources. none
druid.broker.segment.watchedDataSources List of strings Broker watches the segment announcements from nodes serving segments to build cache of which node is serving which segments, this configuration allows to only consider segments being served from a whitelist of dataSources. By default, Broker would consider all datasources. This can be used to configure brokers in partitions so that they are only queryable for specific dataSources. none