18.2. Kafka Data Store Parameters

The Kafka data store differs from most data stores in that the data set is kept entirely in memory. Because of this, the in-memory indexing can be configured at runtime through data store parameters. See Kafka Index Configuration for more information on the available indexing options.

Because configuration options can reference attributes from a particular SimpleFeatureType, it may be necessary to create multiple Kafka data store instances when dealing with multiple schemas.

Use the following parameters for a Kafka data store (required parameters are marked with *):

Parameter	Type	Description
kafka.brokers *	String	Kafka brokers, e.g. localhost:9092
kafka.zookeepers	String	Kafka zookeepers, e.g localhost:2181, used to persist GeoMesa metadata in Zookeeper instead of in Kafka topics. See Zookeeper-less Usage for details.
kafka.catalog.topic	String	The Kafka topic used to store schema metadata (when not using Zookeeper)
kafka.zk.path	String	Zookeeper discoverable path, can be used to namespace feature types (when using Zookeeper)
kafka.producer.config	String	Configuration options for kafka producer, in Java properties format. See Producer Configs
kafka.producer.clear	Boolean	Send a ‘clear’ message on startup. This will cause clients to ignore any data that was in the topic prior to startup
kafka.consumer.config	String	Configuration options for kafka consumer, in Java properties format. See Consumer Configs
kafka.consumer.read-back	String	On start up, read messages that were written within this time frame (vs ignore old messages), e.g. 1 hour. Use Inf to read all messages. If enabled, features will not be available for query until all existing messages are processed. However, feature listeners will still be invoked as normal. See Initial Load (Replay)
kafka.consumer.count	Integer	Number of kafka consumers used per feature type. Set to 0 to disable consuming (i.e. producer only)
kafka.consumer.group-prefix	String	Prefix to use for kafka group ID, to more easily identify particular data stores
kafka.consumer.start-on-demand	Boolean	The default behavior is to start consuming a topic only when that feature type is first requested. This can reduce load if some layers are never queried. Note that care should be taken when setting this to false, as the store will immediately start consuming from Kafka for all known feature types, which may require significant memory overhead.
kafka.topic.partitions	Integer	Number of partitions to use in new kafka topics
kafka.topic.replication	Integer	Replication factor to use in new kafka topics
kafka.serialization.type	String	Internal serialization format to use for kafka messages. Must be one of kryo, avro or avro-native
kafka.cache.expiry	String	Expire features from in-memory cache after this delay, e.g. “10 minutes”. See Feature Expiration
kafka.cache.expiry.dynamic	String	Expire features dynamically based on CQL predicates. See Feature Expiration
kafka.cache.event-time	String	Instead of message time, determine expiry based on feature data. See Feature Event Time
kafka.cache.event-time.ordering	Boolean	Instead of message time, determine feature ordering based on the feature event time. See Feature Event Time
kafka.index.cqengine	String	Use CQEngine-based attribute indices for the in-memory feature cache. See CQEngine Indexing
kafka.index.resolution.x	Integer	Number of bins in the x-dimension of the spatial index, by default 360. See Spatial Index Resolution
kafka.index.resolution.y	Integer	Number of bins in the y-dimension of the spatial index, by default 180. See Spatial Index Resolution
kafka.index.tiers	String	Number and size of tiers used for indexing geometries with extents, in the form x1:y1,x2:y2. See Spatial Index Tiering
kafka.serialization.lazy	Boolean	Use lazy deserialization of features. This may improve processing load at the expense of slightly slower query times
kafka.layer.views	String	Additional views on existing schemas to expose as layers. See Layer Views for details
kafka.metrics.reporters	String	Reporters used to publish Kafka metrics, as TypeSafe config. To use multiple reporters, nest them under the key reporters. See GeoMesa Metrics for details
geomesa.query.loose-bounding-box	Boolean	Use loose bounding boxes, which offer improved performance but are not exact
geomesa.query.audit	Boolean	Audit incoming queries. By default audits are written to a log file
geomesa.security.auths	String	Default authorizations used to query data, comma-separated

18.2.1. Programmatic Access

An instance of a Kafka data store can be obtained through the normal GeoTools discovery methods, assuming that the GeoMesa code is on the classpath.

Map<String, Serializable> parameters = new HashMap<>();
parameters.put("kafka.brokers", "localhost:9092");
org.geotools.api.data.DataStore dataStore =
    org.geotools.api.data.DataStoreFinder.getDataStore(parameters);

More information on using GeoTools can be found in the GeoTools user guide.