Show actual response size in access log for streaming response body

src/AccessLogHandler.php

@@ -5,6 +5,7 @@
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestInterface;
 use React\Promise\PromiseInterface;
+use React\Stream\ReadableStreamInterface;
 
 /**
  * @internal
@@ -28,27 +29,51 @@ public function __invoke(ServerRequestInterface $request, callable $next)
 
         if ($response instanceof PromiseInterface) {
             return $response->then(function (ResponseInterface $response) use ($request) {
-                $this->log($request, $response);
+                $this->logWhenClosed($request, $response);
                 return $response;
             });
         } elseif ($response instanceof \Generator) {
             return (function (\Generator $generator) use ($request) {
                 $response = yield from $generator;
-                $this->log($request, $response);
+                $this->logWhenClosed($request, $response);
                 return $response;
             })($response);
         } else {
-            $this->log($request, $response);
+            $this->logWhenClosed($request, $response);
             return $response;
         }
     }
 
-    private function log(ServerRequestInterface $request, ResponseInterface $response): void
+    /**
+     * checks if response body is closed (not streaming) before writing log message for response
+     */
+    private function logWhenClosed(ServerRequestInterface $request, ResponseInterface $response): void
+    {
+        $body = $response->getBody();
+
+        if ($body instanceof ReadableStreamInterface && $body->isReadable()) {
+            $size = 0;
+            $body->on('data', function (string $chunk) use (&$size) {
+                $size += strlen($chunk);
+            });
+
+            $body->on('close', function () use (&$size, $request, $response) {
+                $this->log($request, $response, $size);
+            });
+        } else {
+            $this->log($request, $response, $body->getSize() ?? strlen((string) $body));
+        }
+    }
+
+    /**
+     * writes log message for response after response body is closed (not streaming anymore)
+     */
+    private function log(ServerRequestInterface $request, ResponseInterface $response, int $responseSize): void
     {
         $this->sapi->log(
             ($request->getServerParams()['REMOTE_ADDR'] ?? '-') . ' ' .
             '"' . $this->escape($request->getMethod()) . ' ' . $this->escape($request->getRequestTarget()) . ' HTTP/' . $request->getProtocolVersion() . '" ' .
-            $response->getStatusCode() . ' ' . $response->getBody()->getSize()
+            $response->getStatusCode() . ' ' . $responseSize
         );
     }
 

tests/AccessLogHandlerTest.php

@@ -6,6 +6,7 @@
 use PHPUnit\Framework\TestCase;
 use React\Http\Message\Response;
 use React\Http\Message\ServerRequest;
+use React\Stream\ThroughStream;
 use function React\Promise\resolve;
 
 class AccessLogHandlerTest extends TestCase
@@ -120,6 +121,48 @@ public function testInvokeWithCoroutineNextPrintsRequestLogWithCurrentDateAndTim
         $generator->next();
     }
 
+    public function testInvokeWithStreamingResponsePrintsRequestLogWithCurrentDateAndTime()
+    {
+        $handler = new AccessLogHandler();
+
+        $stream = new ThroughStream();
+        $request = new ServerRequest('GET', 'http://localhost:8080/users', [], '', '1.1', ['REMOTE_ADDR' => '127.0.0.1']);
+        $response = new Response(200, [], $stream);
+
+        // 2021-01-29 12:22:01.717 127.0.0.1 "GET /users HTTP/1.1" 200 10\n
+        $this->expectOutputRegex("/^\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}\.\d{3} 127\.0\.0\.1 \"GET \/users HTTP\/1\.1\" 200 10" . PHP_EOL . "$/");
+        $handler($request, function () use ($response) { return $response; });
+        $stream->write('hello');
+        $stream->end('world');
+    }
+
+    public function testInvokeWithClosedStreamingResponsePrintsRequestLogWithCurrentDateAndTime()
+    {
+        $handler = new AccessLogHandler();
+
+        $stream = new ThroughStream();
+        $stream->close();
+        $request = new ServerRequest('GET', 'http://localhost:8080/users', [], '', '1.1', ['REMOTE_ADDR' => '127.0.0.1']);
+        $response = new Response(200, [], $stream);
+
+        // 2021-01-29 12:22:01.717 127.0.0.1 "GET /users HTTP/1.1" 200 10\n
+        $this->expectOutputRegex("/^\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}\.\d{3} 127\.0\.0\.1 \"GET \/users HTTP\/1\.1\" 200 0" . PHP_EOL . "$/");
+        $handler($request, function () use ($response) { return $response; });
+    }
+
+    public function testInvokeWithStreamingResponsePrintsNothingIfStreamIsPending()
+    {
+        $handler = new AccessLogHandler();
+
+        $stream = new ThroughStream();
+        $request = new ServerRequest('GET', 'http://localhost:8080/users', [], '', '1.1', ['REMOTE_ADDR' => '127.0.0.1']);
+        $response = new Response(200, [], $stream);
+
+        $this->expectOutputString('');
+        $handler($request, function () use ($response) { return $response; });
+        $stream->write('hello');
+    }
+
     public function testInvokeWithoutRemoteAddressPrintsRequestLogWithDashAsPlaceholder()
     {
         $handler = new AccessLogHandler();