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This covers common database connection-related problems in Sonamu and how to resolve them.

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DB Connection Resource Leak

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Symptoms

Error: remaining connection slots are reserved for non-replication superuser connections
Or 
Error: too many connections for database
This occurs when running development server for a long time or repeating Fixture operations.

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Cause

When DB connections are created and an error occurs, destroy() is not called, causing connections to accumulate without being cleaned up. Problematic code pattern: 
const db = createKnexInstance(config);

// Perform multiple operations
await db.raw("SELECT ...");
await db.raw("UPDATE ...");  // Error occurs here

await db.destroy();  // Never reached

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Solutions

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1. Use try-finally Pattern

const db = createKnexInstance(config);

try {
  await db.raw("SELECT ...");
  await db.raw("UPDATE ...");
  return result;
} finally {
  await db.destroy();  // Executes regardless of error
}

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2. Clean Up Multiple DB Connections

const sourceDB = createKnexInstance(sourceConfig);
const targetDB = createKnexInstance(targetConfig);

try {
  // Perform operations
  const data = await sourceDB.select("*").from("users");
  await targetDB.insert(data).into("users");
  return data;
} finally {
  await targetDB.destroy();
  await sourceDB.destroy();
}

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3. Check Current Connection Count

To check current connection status in PostgreSQL: 
SELECT
  datname,
  count(*) as connections,
  max_conn
FROM pg_stat_activity
JOIN pg_database ON pg_stat_activity.datname = pg_database.datname
WHERE pg_database.datname = 'your_database_name'
GROUP BY datname, max_conn;

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Prevention

  • Always use try-finally when creating DB connections directly
  • Using BaseModel methods automatically manages connections
  • Use FixtureManager methods for Fixture operations (includes automatic cleanup)

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Connection Configuration Error

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Symptoms

Error: connect ECONNREFUSED 127.0.0.1:5432

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Causes

  1. PostgreSQL server is not running
  2. DB configuration in .env file is incorrect
  3. Port number is wrong

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Solutions

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1. Check PostgreSQL Running

# macOS (Homebrew)
brew services list
brew services start postgresql

# Linux (systemd)
sudo systemctl status postgresql
sudo systemctl start postgresql

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2. Check Connection Information

Check .env file: 
DB_HOST=localhost
DB_PORT=5432
DB_USER=postgres
DB_PASSWORD=your_password
DB_NAME=your_database

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3. Manual Connection Test

psql -h localhost -p 5432 -U postgres -d your_database
If successful, psql prompt appears after password input.

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Timeout Error

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Symptoms

Error: Timeout acquiring a connection. The pool is probably full.

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Causes

  1. DB connection pool exhausted
  2. Long-running queries holding connections
  3. Connection pool settings too small

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Solutions

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1. Adjust Connection Pool Settings

sonamu.config.ts: 
export default {
  database: {
    miomock: {
      host: "localhost",
      port: 5432,
      user: "postgres",
      password: "password",
      database: "miomock",
      pool: {
        min: 2,
        max: 10,  // Increase from default
        acquireTimeoutMillis: 30000,  // Increase timeout
        idleTimeoutMillis: 30000
      }
    }
  }
} satisfies SonamuConfig;

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2. Check Long-Running Queries

-- Check currently running queries
SELECT
  pid,
  now() - query_start as duration,
  query
FROM pg_stat_activity
WHERE state = 'active'
ORDER BY duration DESC;

-- Kill specific query
SELECT pg_cancel_backend(pid);  -- Graceful termination
SELECT pg_terminate_backend(pid);  -- Force termination

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3. Check Uncommitted Transactions

-- Check old transactions
SELECT
  pid,
  now() - xact_start as duration,
  state,
  query
FROM pg_stat_activity
WHERE xact_start IS NOT NULL
ORDER BY duration DESC;

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Permission Error

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Symptoms

Error: permission denied for table users

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Solution

-- Check database owner
SELECT d.datname, u.usename
FROM pg_database d
JOIN pg_user u ON d.datdba = u.usesysid
WHERE d.datname = 'your_database';

-- Grant schema permissions
GRANT ALL ON SCHEMA public TO your_user;

-- Grant table permissions
GRANT ALL ON ALL TABLES IN SCHEMA public TO your_user;

-- Grant sequence permissions
GRANT ALL ON ALL SEQUENCES IN SCHEMA public TO your_user;

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Test Environment DB Conflict

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Symptoms

Error: database "miomock_test" already exists
Or 
Error: database "miomock_test" is being accessed by other users

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Causes

  • Previous test didn’t terminate properly, leaving test DB
  • Multiple test processes running simultaneously

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Solutions

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1. Force Delete Test DB

# Terminate all connections and delete DB
psql -U postgres -c "
  SELECT pg_terminate_backend(pid)
  FROM pg_stat_activity
  WHERE datname = 'miomock_test' AND pid <> pg_backend_pid();
"

psql -U postgres -c "DROP DATABASE IF EXISTS miomock_test;"

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2. Isolate Test Execution

package.json: 
{
  "scripts": {
    "test": "vitest run --pool=forks --poolOptions.forks.singleFork=true"
  }
}

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3. Check Test Setup/Teardown

// vitest.config.ts
export default defineConfig({
  test: {
    globalSetup: "./test/setup.ts",
    globalTeardown: "./test/teardown.ts"
  }
});

// test/teardown.ts
export default async function teardown() {
  await DB.clearTestTransaction();
  await DB.closeConnection();
}