The workflow engine Camunda uses caching to improve the performance of the process engine. In Camunda, there are two types of caches: First Level Cache and Second Level Cache.
The first-level cache is the built-in cache of the Camunda engine, which is used to cache data read multiple times in the same transaction. For example, when a process instance ID is used to query multiple tasks, the Camunda engine will cache the query results in the first-level cache to avoid multiple querying of the database. The first-level cache is related to transactions. When a transaction is committed or rolled back, the cache will be cleared.
The second-level cache is an external cache of the Camunda engine, which is used to cache some data that needs to be shared across transactions. For example, data such as process definitions, process instances, and tasks can be cached in the second-level cache to reduce the frequency of database access. Camunda supports multiple second-level cache implementations, including Ehcache, Hazelcast, Infinispan, etc. The use of the second-level cache requires certain configurations, and it is necessary to ensure the consistency and correctness of the cached data during concurrent access.
In Camunda, cache usage can be configured and tuned in the following ways:
1. Configure the size and timeout time of the first-level cache and the second-level cache to adapt to different business scenarios and hardware environments.
2. Configure the cache refresh strategy to ensure the correctness and consistency of the cached data.
3. Monitor the usage of cache and the impact of cache on system performance, and adjust and optimize in time.
In short, caching is an important means for Camunda to improve the performance of the process engine, but it needs to be properly configured and used to avoid inconsistencies or errors in cached data.