druid/docs/content/Broker-Config.md

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Broker Node Configuration

For general Broker Node information, see here.

Runtime Configuration

The broker module uses several of the default modules in Configuration and has the following set of configurations as well:

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
druid.broker.cache.type	local, memcached	The type of cache to use for queries.	local
druid.broker.cache.unCacheable	All druid query types	All query types to not cache.	["groupBy", "select"]
druid.broker.cache.numBackgroundThreads	Non-negative integer	Number of background threads in the thread pool to use for eventual-consistency caching results if caching is used. It is recommended to set this value greater or equal to the number of processing threads. To force caching to execute in the same thread as the query (query results are blocked on caching completion), use a thread count of 0. Setups who use a Druid backend in programatic settings (sub-second re-querying) should consider setting this to 0 to prevent eventual consistency from biting overall performance in the ass. If this is you, please experiment to find out what setting works best.	0

Local Cache

Property	Description	Default
druid.broker.cache.sizeInBytes	Maximum cache size in bytes. Zero disables caching.	0
druid.broker.cache.initialSize	Initial size of the hashtable backing the cache.	500000
druid.broker.cache.logEvictionCount	If non-zero, log cache eviction every logEvictionCount items.	0
druid.broker.cache.numBackgroundThreads	Number of background threads in the thread pool to use for eventual-consistency caching results if caching is used. It is recommended to set this value greater or equal to the number of processing threads. To force caching to execute in the same thread as the query (query results are blocked on caching completion), use a thread count of 0. Setups who use a Druid backend in programatic settings (sub-second re-querying) should consider setting this to 0 to prevent eventual consistency from biting overall performance in the ass. If this is you, please experiment to find out what setting works best.	0

Memcache

Property	Description	Default
druid.broker.cache.expiration	Memcached expiration time.	2592000 (30 days)
druid.broker.cache.timeout	Maximum time in milliseconds to wait for a response from Memcached.	500
druid.broker.cache.hosts	Comma separated list of Memcached hosts <host:port>.	none
druid.broker.cache.maxObjectSize	Maximum object size in bytes for a Memcached object.	52428800 (50 MB)
druid.broker.cache.memcachedPrefix	Key prefix for all keys in Memcached.	druid