Activiti's internal caching mechanism

Purpose of Caching

Activiti uses a caching mechanism primarily to improve performance and reduce frequent database access, thereby speeding up process execution and response times. Caching allows quick access to frequently used data, such as process definitions, process instances, and tasks.

Types of Caching

Activiti's caching mainly includes the following types:

• Process Definition Cache: Used to cache process definitions to avoid loading them from the database each time. Process definitions are usually loaded into the cache during deployment and used when creating process instances.
• Process Instance Cache: Caches currently running process instances to improve access speed. Process instances include the execution state, node information, variables, and other data.
• Task Cache: Caches currently assigned tasks to accelerate task queries and operations. The task cache stores basic information, assignment details, and related variables of tasks.
• Variable Cache: Caches variables in the process to reduce read and write operations to the database. The variable cache ensures quick access and updates to variables during process execution.

Caching Strategy

Activiti's caching strategy can be adjusted through configuration, including cache size, expiration time, and cleaning strategy. Developers can optimize the cache configuration according to specific application scenarios and needs to achieve the best performance.

• Cache Size: The cache size can be set to a fixed size or dynamically adjusted, ensuring that the cache does not occupy too much memory while storing enough hot data.
• Expiration Time: By setting the expiration time of cache items, the retention time of cached data can be controlled to prevent the data from becoming outdated.
• Cleaning Strategy: Uses algorithms like LRU (Least Recently Used) to clean up old data in the cache, ensuring high efficiency.

Cache Implementation

Activiti's cache implementation is based on Java's memory caching mechanism, typically using Java collection classes like HashMap to store cache data. To ensure thread safety and high performance, Activiti uses concurrent collection classes like ConcurrentHashMap for cache implementation.