CircuitBreaker Plugins

withCircuitBreakerPrefix plugin

The CircuitBreaker prefix plugin intercepts calls to a circuit-breaker adapter and transparently prefixes all circuit keys with a configurable string. This enables logical key namespacing without modifying the adapter implementation.

Use cases

• Multi-tenant systems — Prefix circuit keys with a tenant identifier to isolate circuit state between tenants
• Service versioning — Separate circuit state for different API versions
• Environment isolation — Keep development, staging, and production circuit state separate
• Region scoping — Prefix keys with a region identifier in multi-region deployments

How it works

The withCircuitBreakerPrefix function returns a PluginFn that calls enhance on each adapter method that accepts a circuit key. When an enhanced method is invoked, the plugin intercepts the call, prepends the configured prefix to the key argument, and forwards the modified arguments to the original method.

The plugin prefixes keys for the following methods:

Method	Key argument	Pattern
getState	First argument (key)	prefix + key
isolate	First argument (key)	prefix + key
reset	First argument (key)	prefix + key
trackFailure	First argument (key)	prefix + key
trackSuccess	First argument (key)	prefix + key
updateState	First argument (key)	prefix + key

Usage

./samples/with-circuit-breaker-prefix.ts

import { withPlugin } from "eridu-tech/middleware";
import { MemoryCircuitBreakerStorageAdapter } from "eridu-tech/circuit-breaker/memory-circuit-breaker-storage-adapter";
import { DatabaseCircuitBreakerAdapter } from "eridu-tech/circuit-breaker/database-circuit-breaker-adapter";
import { withCircuitBreakerPrefix } from "eridu-tech/circuit-breaker/plugins";

const adapter = new DatabaseCircuitBreakerAdapter({
    adapter: new MemoryCircuitBreakerStorageAdapter(),
});

// Apply the prefix plugin to the adapter
const prefixedAdapter = withPlugin(
    adapter,
    withCircuitBreakerPrefix("service-a:"),
);

Before/after behavior

Before — Circuit keys are used as-is:

./samples/unprefixed-circuit-lookup.ts

import { MemoryCircuitBreakerStorageAdapter } from "eridu-tech/circuit-breaker/memory-circuit-breaker-storage-adapter";
import { DatabaseCircuitBreakerAdapter } from "eridu-tech/circuit-breaker/database-circuit-breaker-adapter";

const adapter = new DatabaseCircuitBreakerAdapter({
    adapter: new MemoryCircuitBreakerStorageAdapter(),
});

await adapter.getState("api:users");
// -> looks up circuit "api:users"

After — Circuit keys are automatically prefixed:

./samples/prefixed-circuit-lookup.ts

import { withPlugin } from "eridu-tech/middleware";
import { MemoryCircuitBreakerStorageAdapter } from "eridu-tech/circuit-breaker/memory-circuit-breaker-storage-adapter";
import { DatabaseCircuitBreakerAdapter } from "eridu-tech/circuit-breaker/database-circuit-breaker-adapter";
import { withCircuitBreakerPrefix } from "eridu-tech/circuit-breaker/plugins";

const adapter = new DatabaseCircuitBreakerAdapter({
    adapter: new MemoryCircuitBreakerStorageAdapter(),
});

// Apply the prefix plugin to the adapter
const prefixedAdapter = withPlugin(
    adapter,
    withCircuitBreakerPrefix("service-a:"),
);

await prefixedAdapter.getState("api:users");
// -> looks up circuit "service-a:api:users"

danger

Because withPlugin uses enhance under the hood, the same edge case applies: if one enhanced method internally calls another enhanced method via this, the middleware will apply twice. Be mindful of inter-method calls when applying plugins that enhance multiple methods on the same instance.

info

For more information about the withPlugin function and applying plugins to adapters, see the Middleware plugin documentation.