mirror of https://github.com/apache/druid.git
67 lines
3.1 KiB
Markdown
67 lines
3.1 KiB
Markdown
---
|
|
id: kafka-extraction-namespace
|
|
title: "Apache Kafka Lookups"
|
|
---
|
|
|
|
<!--
|
|
~ Licensed to the Apache Software Foundation (ASF) under one
|
|
~ or more contributor license agreements. See the NOTICE file
|
|
~ distributed with this work for additional information
|
|
~ regarding copyright ownership. The ASF licenses this file
|
|
~ to you under the Apache License, Version 2.0 (the
|
|
~ "License"); you may not use this file except in compliance
|
|
~ with the License. You may obtain a copy of the License at
|
|
~
|
|
~ http://www.apache.org/licenses/LICENSE-2.0
|
|
~
|
|
~ Unless required by applicable law or agreed to in writing,
|
|
~ software distributed under the License is distributed on an
|
|
~ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
|
|
~ KIND, either express or implied. See the License for the
|
|
~ specific language governing permissions and limitations
|
|
~ under the License.
|
|
-->
|
|
|
|
> Lookups are an [experimental](../experimental.md) feature.
|
|
|
|
To use this Apache Druid extension, [include](../../development/extensions.md#loading-extensions) `druid-lookups-cached-global` and `druid-kafka-extraction-namespace` in the extensions load list.
|
|
|
|
If you need updates to populate as promptly as possible, it is possible to plug into a Kafka topic whose key is the old value and message is the desired new value (both in UTF-8) as a LookupExtractorFactory.
|
|
|
|
```json
|
|
{
|
|
"type":"kafka",
|
|
"kafkaTopic":"testTopic",
|
|
"kafkaProperties":{"zookeeper.connect":"somehost:2181/kafka"}
|
|
}
|
|
```
|
|
|
|
|Parameter|Description|Required|Default|
|
|
|---------|-----------|--------|-------|
|
|
|`kafkaTopic`|The Kafka topic to read the data from|Yes||
|
|
|`kafkaProperties`|Kafka consumer properties. At least"zookeeper.connect" must be specified. Only the zookeeper connector is supported|Yes||
|
|
|`connectTimeout`|How long to wait for an initial connection|No|`0` (do not wait)|
|
|
|`isOneToOne`|The map is a one-to-one (see [Lookup DimensionSpecs](../../querying/dimensionspecs.md))|No|`false`|
|
|
|
|
The extension `kafka-extraction-namespace` enables reading from a Kafka feed which has name/key pairs to allow renaming of dimension values. An example use case would be to rename an ID to a human readable format.
|
|
|
|
The consumer properties `group.id` and `auto.offset.reset` CANNOT be set in `kafkaProperties` as they are set by the extension as `UUID.randomUUID().toString()` and `smallest` respectively.
|
|
|
|
See [lookups](../../querying/lookups.md) for how to configure and use lookups.
|
|
|
|
## Limitations
|
|
|
|
Currently the Kafka lookup extractor feeds the entire Kafka stream into a local cache. If you are using on-heap caching, this can easily clobber your java heap if the Kafka stream spews a lot of unique keys.
|
|
off-heap caching should alleviate these concerns, but there is still a limit to the quantity of data that can be stored.
|
|
There is currently no eviction policy.
|
|
|
|
## Testing the Kafka rename functionality
|
|
|
|
To test this setup, you can send key/value pairs to a Kafka stream via the following producer console:
|
|
|
|
```
|
|
./bin/kafka-console-producer.sh --property parse.key=true --property key.separator="->" --broker-list localhost:9092 --topic testTopic
|
|
```
|
|
|
|
Renames can then be published as `OLD_VAL->NEW_VAL` followed by newline (enter or return)
|