fix(backend): replace honoLogger with pino-based HTTP logger

backend/src/index.ts

@@ -6,14 +6,14 @@
 import { serve } from '@hono/node-server';
 import { Hono } from 'hono';
 import { cors } from 'hono/cors';
-import { logger as honoLogger } from 'hono/logger';
 import { prettyJSON } from 'hono/pretty-json';
 import { serveStatic } from '@hono/node-server/serve-static';
 import 'dotenv/config';
 import { ProxyAgent, setGlobalDispatcher } from 'undici';
 import { createLogger, generateTraceId } from './lib/logger';
 import { prisma } from './lib/prisma';
 import { traceMiddleware } from './lib/trace-middleware';
+import { httpLogger } from './lib/http-logger';
 
 // Create a startup logger with shared traceId for all startup logs
 const startupTraceId = generateTraceId();
@@ -235,7 +235,7 @@ const app = new Hono();
 // Middleware
 // Trace middleware must be first to capture traceId for all subsequent logging
 app.use('*', traceMiddleware());
-app.use('*', honoLogger());
+app.use('*', httpLogger());
 app.use('*', prettyJSON());
 
 // CORS must be before all routes

backend/src/lib/http-logger.ts

@@ -0,0 +1,63 @@
+/**
+ * HTTP Request Logger Middleware
+ *
+ * Provides structured JSON logging for HTTP requests using Pino.
+ * Replaces Hono's default text logger for production compatibility.
+ *
+ * Output format:
+ *   {"level":"info","time":1735368000,"service":"m3w-backend","region":"jp",
+ *    "source":"http.request","col1":"http","col2":"GET","method":"GET",
+ *    "path":"/api/health","status":200,"duration":12,"msg":"GET /api/health 200 12ms"}
+ */
+
+import type { Context, Next } from 'hono';
+import { logger } from './logger';
+
+/**
+ * HTTP logger middleware using Pino
+ *
+ * Logs incoming requests and outgoing responses with:
+ * - Method, path, status code
+ * - Response duration in milliseconds
+ * - Structured fields for Loki/Grafana filtering
+ *
+ * @returns Hono middleware function
+ */
+export function httpLogger() {
+  return async (c: Context, next: Next) => {
+    const start = Date.now();
+    const method = c.req.method;
+    const path = c.req.path;
+
+    // Get traceId from context (set by traceMiddleware)
+    const traceId = c.get('traceId') as string | undefined;
+
+    await next();
+
+    const duration = Date.now() - start;
+    const status = c.res.status;
+
+    // Build log entry with structured fields
+    const logEntry = {
+      source: 'http.request',
+      col1: 'http',
+      col2: method,
+      method,
+      path,
+      status,
+      duration,
+      ...(traceId && { traceId }),
+    };
+
+    // Log at appropriate level based on status code
+    const message = `${method} ${path} ${status} ${duration}ms`;
+
+    if (status >= 500) {
+      logger.error(logEntry, message);
+    } else if (status >= 400) {
+      logger.warn(logEntry, message);
+    } else {
+      logger.info(logEntry, message);
+    }
+  };
+}