database

A cache store in a Gloo Repo, on PostgreSQL or SQLite, through howdy/database. Every node using the same database shares the entries and their invalidations.

import howdy/cache
import howdy/cache/database as cache_database

let assert Ok(Nil) = migration.run(db, [cache_database.schema()])
let assert Ok(store) = cache_database.store(db)
let app_cache = cache.new(store)

Reading an entry is one query, so this store pays off for work that costs more than a query: several joined queries, a call to another service, rendering a large page. On PostgreSQL the entry tables are UNLOGGED: writes skip the write-ahead log, and a crash empties them, which for a cache is only a cold start.

Expired entries are deleted every five minutes by a process that lives as long as the process that called store, so call it in main. invalidate also deletes the entries carrying the tags. The table of tag versions keeps one row per tag ever invalidated; it has to, since forgetting a version could make an old entry current again.

Values

schema

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pub fn schema() -> migration.Package

The howdy_cache_ tables. Run with howdy/migration during deployment.

store

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pub fn store(
  repo: repo.Repo,
) -> Result(cache.Store, service.Error)

A store over this Repo, once its schema is checked, with a process deleting expired entries every five minutes. The process stops when the caller exits.

sweep

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pub fn sweep(repo: repo.Repo) -> Result(Int, service.Error)

Delete expired entries, a thousand at a time, and return how many went.