Feature flags
Cache
In @workertown/feature-flags, the cache is used to in front of certain storage queries to improve performance.
When an ask operation is performed, the service will (if the cache is enabled - it is by default) search for a cached version of the current flags. If a cached version is found, it will not hit the storage and instead use the cached set of flags.
When a feature flag is added/updated/deleted, the service will clear the cache.
For more information on how cache works in Workertown services more generally, see cache
CacheAdapter
The CacheAdapter interface is defined as follows:
interface FlagCondition {
field: string;
operator: "eq" | "neq" | "gt" | "gte" | "lt" | "lte" | "in" | "nin";
value: string | number | boolean | string[] | number[] | boolean[];
}
interface Flag {
name: string;
description?: string;
enabled: boolean;
conditions?: FlagCondition[];
createdAt: Date;
updatedAt: Date;
}
declare class CacheAdapter {
get<Flag[]>(key: string): Promise<T | null>;
set(key: string, value: Flag, ttl?: number): Promise<void>;
delete(key?: string): Promise<void>;
}
Built-in CacheAdapters
@workertown/feature-flags provides several built-in CacheAdapters that can be used via the runtime configuration option.
KVCacheAdapter
The KVCacheAdapter is the default CacheAdapter and is used when no other CacheAdapter is specified. It uses Cloudflare Workers KV to store the cached data.
import { featureFlags } from "@workertown/feature-flags";
import { KVCacheAdapter } from "@workertown/feature-flags/cache/kv";
import { StorageAdapter } from "@workertown/feature-flags/storage";
export default featureFlags({
runtime: (options, env) => ({
cache: new KVCacheAdapter({ kv: env.KV }), // `kv` is the KVNamespace bound to the Cloudflare Worker to use for the cache
storage: new StorageAdapter(/* ... */),
}),
});
UpstashRedisCacheAdapter
Coming soon...
MemoryCacheAdapter
The MemoryCacheAdapter is a simple CacheAdapter that stores the cached data in memory. It is not recommended for production use, but can be useful for development and testing.
import { featureFlags } from "@workertown/feature-flags";
import { MemoryCacheAdapter } from "@workertown/feature-flags/cache/memory";
import { StorageAdapter } from "@workertown/feature-flags/storage";
export default featureFlags({
runtime: (options, env) => ({
cache: new MemoryCacheAdapter(),
storage: new StorageAdapter(/* ... */),
}),
});
NoOpCacheAdapter
The NoOpCacheAdapter is a CacheAdapter that does nothing. It is provided simply for situations where you want to provide a CacheAdapter instance but don't want it to do anything.
import { featureFlags } from "@workertown/feature-flags";
import { NoOpCacheAdapter } from "@workertown/feature-flags/cache/no-op";
import { StorageAdapter } from "@workertown/feature-flags/storage";
export default featureFlags({
runtime: (options, env) => ({
cache: new NoOpCacheAdapter(),
storage: new StorageAdapter(/* ... */),
}),
});
Custom CacheAdapters
You can also provide your own custom CacheAdapter by extending the CacheAdapter class.
import { featureFlags } from "@workertown/feature-flags";
import { CacheAdapter, type Flag } from "@workertown/feature-flags/cache";
import { StorageAdapter } from "@workertown/feature-flags/storage";
class CustomCacheAdapter extends CacheAdapter {
async get(key: string) { /* .. */ },
async set(key: string, value: Flag, ttl?: number) { /* .. */ },
async delete(key?: string) { /* .. */ },
}
export default featureFlags({
runtime: (options, env) => ({
cache: new CustomCacheAdapter(),
storage: new StorageAdapter(/* ... */),
}),
});