Server response caching

Weave provides server response caching to improve performance when you run repeated queries or work with limited network bandwidth. This article explains when caching helps, how to enable it, which requests Weave caches, and how the cache uses disk space, so you can decide whether to turn it on and plan for its storage footprint. The feature is deactivated by default.

When to use caching

Server response caching is helpful when:

• You frequently run the same queries.
• You have limited network bandwidth.
• You’re working in an environment with high latency.
• You’re developing offline and want to cache responses for later use.

This feature is useful when you run repeated evaluations on a dataset, because Weave can cache the dataset between runs.

Enable caching

To enable caching, set the following environment variables. WEAVE_USE_SERVER_CACHE turns the cache on, and the other variables let you tune its size and location.

# Enable server response caching
export WEAVE_USE_SERVER_CACHE=true

# Set cache size limit (default is 1 GB)
export WEAVE_SERVER_CACHE_SIZE_LIMIT=1000000000

# Set cache directory (optional, defaults to temporary directory)
export WEAVE_SERVER_CACHE_DIR=/path/to/cache

Caching behavior

This section describes which server requests Weave caches, so you can predict which operations benefit from caching. The feature caches idempotent requests against the server. Weave caches the following requests:

• obj_read
• table_query
• table_query_stats
• refs_read_batch
• file_content_read

Cache size and storage details

Use this section to estimate the disk space the cache requires, so you can size WEAVE_SERVER_CACHE_SIZE_LIMIT for your environment. WEAVE_SERVER_CACHE_SIZE_LIMIT (in bytes) controls the cache size. The actual disk space used consists of three components:

• A constant 32 KB checksum file.
• A Write-Ahead Log (WAL) file up to ~4 MB per running client. Weave removes the WAL file automatically when the program exits.
• The main database file, which is at least 32 KB and at most WEAVE_SERVER_CACHE_SIZE_LIMIT.

Total disk space used:

• While running >= 32 KB + ~4 MB + cache size.
• After exit >= 32 KB + cache size.

For example, with a 5 MB cache limit:

• While running: ~9 MB maximum.
• After exit: ~5 MB maximum.

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Performance