Cloudflare DevelopersCD
Cloudflare Developers•3y ago
eshnil

Can I use Env for caching database results?

The HelloWorld worker example recommends using the Env object to store the router which is initialized once and never modified:

async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    if(env.router === undefined) env.router = buildRouter(env);
    return env.router.handle(request);
}


My API depends on some database values (policies) which are very rarely changed, but when they do, they need to be respected immediately and everywhere. I thought of using Env for this as well and modified the above to:

async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    if(env.router === undefined) env.router = buildRouter(env);
    if(env.policies === undefined) env.policies = await fetchPolicies(env);
    return env.router.handle(request);
}


and I defined a /refresh API that I will call explicitly when policies change in db like this:

  router.get("/refresh", async (request) => {
    env.policies = await fetchPolicies(env);
    return new Response("policies refreshed!");
  });


This seems to work fine locally. But I am not sure if this will work correctly in production. Given that the worker isolates are deployed at multiple locations across the globe, my /refresh API will only reach one of the worker instances and all other instances will continue to have stale data in their env.policies.

Is there a way to cache DB values while able to invalidate them globally at once?
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