effect-patterns-resource-management

Effect-TS Patterns: Resource Management

This skill provides 8 curated Effect-TS patterns for resource management. Use this skill when working on tasks related to:

• resource management
• Best practices in Effect-TS applications
• Real-world patterns and solutions

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🟢 Beginner Patterns

Safely Bracket Resource Usage with acquireRelease

Rule: Bracket the use of a resource between an acquire and a release effect.

Good Example:

import { Effect, Console } from "effect";

// A mock resource that needs to be managed
const getDbConnection = Effect.sync(() => ({ id: Math.random() })).pipe(
  Effect.tap(() => Effect.log("Connection Acquired"))
);

const closeDbConnection = (conn: {
  id: number;
}): Effect.Effect<void, never, never> =>
  Effect.log(`Connection ${conn.id} Released`);

// The program that uses the resource
const program = Effect.acquireRelease(
  getDbConnection, // 1. acquire
  (connection) => closeDbConnection(connection) // 2. cleanup
).pipe(
  Effect.tap((connection) =>
    Effect.log(`Using connection ${connection.id} to run query...`)
  )
);

Effect.runPromise(Effect.scoped(program));

/*
Output:
Connection Acquired
Using connection 0.12345... to run query...
Connection 0.12345... Released
*/

Explanation: By using Effect.acquireRelease, the closeDbConnection logic is guaranteed to run after the main logic completes. This creates a self-contained, leak-proof unit of work that can be safely composed into larger programs.

Anti-Pattern:

Using a standard try...finally block with async/await. While it handles success and failure cases, it is not interruption-safe. If the fiber executing the Promise is interrupted by Effect's structured concurrency, the finally block is not guaranteed to run, leading to resource leaks.

// ANTI-PATTERN: Not interruption-safe
async function getUser() {
  const connection = await getDbConnectionPromise(); // acquire
  try {
    return await useConnectionPromise(connection); // use
  } finally {
    // This block may not run if the fiber is interrupted!
    await closeConnectionPromise(connection); // release
  }
}