feat(encoding): add gzip compression to outgoing envelopes

agent/src/EnvelopeForwarder.php

@@ -92,17 +92,27 @@ public function forward(Envelope $envelope): PromiseInterface
             'sentry_key=' . $dsn->getPublicKey(),
         ];
 
-        // @TODO: Implement any number of missing options like the user-agent, encoding, proxy etc.
+        $headers = [
+            'User-Agent' => $client,
+            'Content-Type' => Envelope::CONTENT_TYPE,
+            'X-Sentry-Auth' => 'Sentry ' . implode(', ', $authHeader),
+        ];
+
+        $body = (string) $envelope;
+
+        if (\extension_loaded('zlib')) {
+            $compressedBody = gzcompress($body, -1, \ZLIB_ENCODING_GZIP);
+
+            if ($compressedBody !== false) {
+                $headers['Content-Encoding'] = 'gzip';
+                $body = $compressedBody;
+            }
+        }
 
-        // @TODO: We might want to replace this Browser API with a cURL implementation using curl_multi_exec
         return (new Browser())->withTimeout($this->timeout)->post(
             $dsn->getEnvelopeApiEndpointUrl(),
-            [
-                'User-Agent' => $client,
-                'Content-Type' => Envelope::CONTENT_TYPE,
-                'X-Sentry-Auth' => 'Sentry ' . implode(', ', $authHeader),
-            ],
-            (string) $envelope
+            $headers,
+            $body
         )->then(function (ResponseInterface $response) use ($rateLimiter) {
             $rateLimiter->handleResponse(
                 new Response($response->getStatusCode(), $response->getHeaders(), $response->getStatusCode() > 400 ? $response->getBody()->getContents() : '')

agent/tests/AgentForwardingTest.php

@@ -61,6 +61,27 @@ public function testAgentForwardsMultipleEnvelopesToUpstream(): void
         $this->assertEquals(2, $serverOutput['request_count']);
     }
 
+    public function testAgentCompressesEnvelopeToUpstream(): void
+    {
+        if (!\extension_loaded('zlib')) {
+            $this->markTestSkipped('The zlib extension is required to test envelope compression.');
+        }
+
+        $serverAddress = $this->startTestServer();
+
+        $dsn = "http://publickey:@{$serverAddress}/200";
+
+        $this->startTestAgent();
+        $this->sendEnvelopeToAgent($this->createEnvelope($dsn, 'Compressed message'));
+        $this->stopTestAgent();
+
+        $serverOutput = $this->stopTestServer();
+
+        $this->assertTrue($serverOutput['compressed']);
+        $this->assertEquals('gzip', $serverOutput['headers']['Content-Encoding']);
+        $this->assertStringContainsString('Compressed message', $serverOutput['body']);
+    }
+
     public function testAgentRespectsRateLimiting(): void
     {
         $serverAddress = $this->startTestServer();

bin/sentry-agent.sig

@@ -1 +1 @@
-F3CE4B37DC4AC5C3890CC9497A95351E29641DA3BAD0699B727A8D77002C6B36913EB82B55ACB1BA683D27CBAF123007D2CE68AA10773CF4012292D38E5F1904
+C779A799D4389C7E52048F1271B64B01DFFBD75C59E111C5DB180004E980D2CD6F56D59FDD14825EE3F6F8F002F5405D0CB97FB46199D730C7FDB77D4BB5A9A4