Cache Kafka records — Conduktor Gateway

The cache Interceptor doesn’t support incremental fetch sessions, which are on by default since Gateway v3.21.0. If you use it, set GATEWAY_FEATURE_FLAGS_INCREMENTAL_FETCH_SESSIONS_ENABLED=false. See limitations.

Overview

The cache is designed to improve the performance of record retrieval in a Kafka by caching records. It intercepts produce and fetch requests, caching produced records and serving fetched records from the cache, if available.

Benefits

Benefits include:

Improved performance. By serving fetched records from the cache, subsequent fetch requests can be served faster, reducing the overall latency and improving the response time for clients.
Reduced load on Kafka cluster. With the cache Interceptor in place, the Kafka cluster experiences reduced load during fetch requests since a portion of the requests can be satisfied from the cache directly, reducing the number of requests hitting the cluster.
Enhanced scalability. The cache Interceptor provides an additional layer of scalability by distributing the workload between the cache and the Kafka cluster. It can handle a higher volume of fetch requests without overwhelming the Kafka cluster.

How the cache works

Produced and fetched records both fill the cache. Gateway caches records after a successful produce (except with acks=0), and caches records the cluster returns for fetch requests that miss the cache.
Cache entries are keyed by service account name. Within a Virtual Cluster, Gateway doesn’t serve records cached for one service account to another.
Transactions bypass the cache. Gateway doesn’t cache transactional produce requests and doesn’t serve read_committed fetch requests from the cache.
Errors aren’t cached. Gateway only caches responses without errors.

Limitations

With incremental fetch sessions on, a consumer reading through the cache Interceptor can stop receiving records from some partitions. It can also open a new fetch session each time the cache answers a whole fetch, which adds load on the Kafka cluster. Set GATEWAY_FEATURE_FLAGS_INCREMENTAL_FETCH_SESSIONS_ENABLED=false to avoid this.

Consumer offsets

The cache Interceptor doesn’t intercept offset commit or offset fetch requests. Group membership, rebalances and offset commits go to the Kafka cluster unchanged, including for consumers served from the cache.

Configuration options

Config	Type	Default	Description
topic	String	`.*`	Topic regex, topic that match this regex will have the Interceptor applied. If no value is set, it will be applied to all topics.
cacheConfig	Cache config		Configuration for cache.

CacheConfig

Config	Type	Description
type	enum (IN_MEMORY, ROCKSDB)	Default: ROCKSDB.
rocksdbConfig	Rocksdb config	Configuration for RocksDB cache.
inMemConfig	InMem config	Configuration for in-memory cache.

RocksdbConfig

Config	Type	Default	Description
dbPath	String	`caching_storage`	Path to RocksDB database.
cacheSize	long	`104857600`	RocksDB cache size in bytes (default: 100 MB).

InMemConfig

Config	Type	Default	Description
cacheSize	int	`10000`	Maximum number of entries in the in-memory cache.
expireTimeMs	long	`300000`	Cache expiration time in milliseconds (5 minutes).

Example

curl
Conduktor CLI

curl \
  --request PUT \
  --url 'http://localhost:8888/gateway/v2/interceptor' \
  --header 'Authorization: Basic YWRtaW46Y29uZHVrdG9y' \
  --header 'Content-Type: application/json' \
  --data-raw '{
  "kind": "Interceptor",
  "apiVersion": "gateway/v2",
  "metadata": {
    "name": "myCacheInterceptor"
  },
  "spec": {
    "pluginClass": "io.conduktor.gateway.interceptor.CacheInterceptorPlugin",
    "priority": 100,
    "config": {
      "topic": ".*",
      "cacheConfig": {
        "type": "ROCKSDB",
        "rocksdbConfig": {
          "dbPath": "/caching_storage",
          "cacheSize": 104857600
        }
      }
    }
  }
}'

apiVersion: gateway/v2
kind: Interceptor
metadata:
  name: myCacheInterceptor
  scope:
    vCluster: passthrough
spec:
  pluginClass: io.conduktor.gateway.interceptor.CacheInterceptorPlugin
  priority: 100
  config:
    topic: ".*"
    cacheConfig:
      type: ROCKSDB
      rocksdbConfig:
        dbPath: /caching_storage
        cacheSize: 104857600

Apply with:

conduktor apply -f cache-interceptor.yaml

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Cache Kafka records — Conduktor Gateway

Overview

Benefits

How the cache works

Limitations

Consumer offsets

Configuration options

CacheConfig

RocksdbConfig

InMemConfig

Example

​Overview

​Benefits

​How the cache works

​Limitations

​Consumer offsets

​Configuration options

​CacheConfig

​RocksdbConfig

​InMemConfig

​Example

Overview

Benefits

How the cache works

Limitations

Consumer offsets

Configuration options

CacheConfig

RocksdbConfig

InMemConfig

Example