Singleton with Qwik

index.ts

import type { PostgresJsDatabase } from 'drizzle-orm/postgres-js';

import type * as schema from './schema';

let _db!: PostgresJsDatabase<typeof schema> | null;

export function getDb(): PostgresJsDatabase<typeof schema> {
  if (!_db) {
    throw new Error('DB is not set in the singleton.');
  }

  return _db;
}

export function initializeDbIfNeeded(
  factory: () => PostgresJsDatabase<typeof schema> | null,
): void {
  if (!_db) {
    _db = factory();
  }
}

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import type { RequestHandler } from '@builder.io/qwik-city';
import type { EnvGetter } from '@builder.io/qwik-city/middleware/request-handler';
import { drizzle } from 'drizzle-orm/postgres-js';
import postgres from 'postgres';
import { initializeDbIfNeeded } from '~/infrastructure/db';
import * as schema from '~/infrastructure/db/schema';
import { LoggerFactory } from '~/utils/logging/LoggerFactory';

export const onRequest: RequestHandler = async ({ env }) => {
  initializeDbIfNeeded(initDatabaseClient(env));
};

const initDatabaseClient = (env: EnvGetter) => () => {
  try {
    const host = env.get('DATABASE_HOST')!;
    const port = parseInt(env.get('DATABASE_PORT')!, 10);
    const name = env.get('DATABASE_NAME')!;
    const username = env.get('DATABASE_USERNAME')!;
    const password = env.get('DATABASE_PASSWORD')!;
    const isToLogQuery = env.get('IS_TO_LOG_QUERY') === 'true';

    const queryClient = postgres({
      host: host,
      port: port,
      database: name,
      username: username,
      password: password,
    });

    return drizzle(queryClient, {
      schema,
      logger: isToLogQuery
        ? {
            logQuery(query: string, params: unknown[]): void {
              LoggerFactory.getLogger().debug({
                message: 'Debugging drizzle query',
                query,
                params,
              });
            },
          }
        : undefined,
    });
  } catch (e) {
    LoggerFactory.getLogger().fatal({
      message: 'Error initializing db.',
      err: e,
    });
    return null;
  }
};