fastcache

fastcache is a simple response caching package that plugs into fastglue. The Cached() middleware can be wrapped around fastglue GET handlers that need to serve cached bytes for a request.

The ClearGroup() handler is meant for invalidating cache, for wrapping POST / PUT / DELETE handlers. It supports arbitrary backend storage implementations and ships with redigo/go-redis store implementations.

Concepts

namespace (fastcache.Options.NamespaceKey).

All cached items are saved under a namespace. For authenticated calls, this is most commonly the user ID. So, all GET requests for a user XX1234 like orders, marketwatch, profile etc. may be namespaced under a XX1234 key in the store.

fastcache.Options.NamespaceKey is the name of the key that'll have the name of the namespace in a RequestCtx.UserValue(NamespaceKey). This UserValue should be set by another middleware, such as the auth middleware, before the Cached() middleware is executed. For example, RequestCtx.SetUerValue("user_id", "XX1234") where user_id is the NamespaceKey. For handlers with params like /orders/:user_id, this is taken care of by the router.

group

Cache for different URIs of the same type can be grouped under a single name so that the cache for a group can be deleted in one go when something changes. For instance, orders and tradebook handlers can be grouped "orders" and different marketwatch calls can be grouped under "mw".

Middlewares

Cached() is the middleware for GET calls that does caching, 304 serving etc.

ClearGroup() is middleware handlers for POST / PUT / DELETE methods that are meant to clear cache for GET calls.

Manual cache clearing

The .Del() and .DelGroup() can be used to manually clear cached items when handler based clearing isn't sufficient.

Example

# Install fastcache.
go get -u github.com/zerodha/fastcache/v4

# Install a store. Stores are separate packages themselves.
go get -u github.com/zerodha/fastcache/stores/goredis/v9

    fc := fastcache.New(redis.New(pool))

    // Long cache options.
    long := &fastcache.Options{
        NamespaceKey: "user_id",
        ETag: true,
    }
    short := &fastcache.Options{
        NamespaceKey: "user_id",
        TTL: time.Second * 60,
        ETag: true,
    }

    g.GET("/margins", auth(fc.Cached(handleGetMargins, short, "margins")))
    g.GET("/margins/:segment", auth(fc.Cached(handleGetMargins, short, "margins")))

    g.GET("/orders", auth(fc.Cached(handleGetMargins, long, "orders")))
    g.GET("/orders", auth(fc.Cached(handleGetMargins, short, "trades")))

    // Clear the orders group. Multiple groups can be specified like: orders, positions ...
    g.DELETE("/orders/:order_id",auth(app.respcache.ClearGroup(handleDeleteMarketwatchItems, short, []string{"orders"})))

Dev Notes

Running Tests

    go test -v github.com/zerodha/fastcache...

Running Cluster Tests

Cluster tests require testcontainers (and docker) to run redis containers.

Therefore, we have kept the cluster tests in a separate file and they are tagged with clustertest. If you want to run the cluster tests, you need to have docker installed and running.

After that you can simply run the tests with the following command:

    go test -tags clustertest -v github.com/zerodha/fastcache...

We also provide a redis-cluster-docker-compose.yml file that can be used to start a redis cluster for local testing.

    docker-compose -f redis-cluster-docker-compose.yml up -d