dache

Introduction

This is a super simple and not very feature-complete durable cache (dache). Right now, only in-memory and postgres durability engines are supported.

Getting started

FROM tombailey256/dache:0.3.0

# you can redact your cache keys so they don't show up in the request logs
ENV LOGGING_REDACT_KEYS="false"
ENV DURABILITY_ENGINE="postgres"
ENV POSTGRES_HOST="postgres"
ENV POSTGRES_PORT=5432
ENV POSTGRES_USER="user"
ENV POSTGRES_PASSWORD="password"
ENV POSTGRES_DATABASE="database"

ENV PORT = 8080

Note that currently, dache does NOT support horizontal scaling. If you run dache on more than one node, even with the same durability engine, you will get unexpected results.

Rest API

Get entry

$> curl -XGET localhost/dache/myKey
200 OK
{
  "value": "myValue"
}

Set entry

$> curl -XPOST localhost/dache/myKey -d { "value": "myValue", "expiry": 1735689600 }
204 No content

expiry is an optional unix timestamp (UTC, seconds since 1970). If you don't give an expiry time, the entry will remain in the cache until a delete operation happens.

Delete entry

$> curl -XDELETE localhost/dache/myKey
204 No content

Durability

Dache is able to survive crashes, node failure, etc by storing messages using a durability engine.

When dache starts, it creates an in-memory cache so it can skip the durability engine and reduce latency for read options. However, set and delete operations still require interaction with the durability engine in order to support durability.

Note, if the durability engine is unavailable after dache has populated it's in-memory cache, read operations will succeed but set and delete operations will fail.

The following durability engines are supported:

In-memory

Stores entries in-memory. There is no durability if dache is restarted or crashes.

export DURABILITY_ENGINE="memory"

Postgres

export DURABILITY_ENGINE="postgres"
export POSTGRES_HOST="postgres"
export POSTGRES_PORT=5432
export POSTGRES_USER="user"
export POSTGRES_PASSWORD="password"
export POSTGRES_DATABASE="database"

Health check

Dache has a built-in health check endpoint (/health) to confirm that it is working correctly. At the moment, it does NOT confirm that the durability engine is working correctly.

Future work

1. Better health checking
2. Metrics/observability?