Don't log web's Squid warm-up request as a failure

src/main/java/com/testingbot/tunnel/proxy/HttpLogHandler.java

@@ -124,7 +124,7 @@ private void log(Request request, Response response, String requestId, long star
         boolean failed = failure != null || status >= 500;
         // BODY is refused for this module, so it can only arrive here by mistake; treat it as
         // HEADERS rather than silently logging nothing.
-        if (mode == Mode.ERRORS && !failed) {
+        if (mode == Mode.ERRORS && (!failed || isSquidInternal(request))) {
             return;
         }
 
@@ -149,6 +149,19 @@ private void log(Request request, Response response, String requestId, long star
         LOG.log(failed ? Level.WARNING : Level.INFO, line.toString());
     }
 
+    /**
+     * Squid's own requests through the tunnel, which fail by design. Web warms up every new
+     * tunnel with {@code GET http://127.0.0.1:1/squid-internal-tunnel-warmup} through both of
+     * Squid's ports, to absorb the cold-start 502 before a customer's first request does. Port 1
+     * is refused, so each answers 502 here, and printed a WARNING with headers on every start
+     * that read as a failed tunnel. Only the default {@code errors} mode drops them: {@code url}
+     * and {@code headers} asked for every request.
+     */
+    private static boolean isSquidInternal(Request request) {
+        String path = request.getHttpURI().getPath();
+        return path != null && path.startsWith("/squid-internal");
+    }
+
     /** CONNECT carries an authority rather than a URL; log whichever the request actually has. */
     private static String target(Request request) {
         String authority = request.getHttpURI().getAuthority();

src/test/java/com/testingbot/tunnel/integration/HttpLoggingTest.java

@@ -204,9 +204,13 @@ private String proxyGetEchoing(String extraHeaders) throws Exception {
     }
 
     private void proxyGet(String extraHeaders) throws Exception {
+        proxyGet("/page", extraHeaders);
+    }
+
+    private void proxyGet(String path, String extraHeaders) throws Exception {
         try (Socket socket = new Socket("127.0.0.1", proxyPort)) {
             socket.setSoTimeout(10_000);
-            String request = "GET http://127.0.0.1:" + originPort + "/page HTTP/1.1\r\n"
+            String request = "GET http://127.0.0.1:" + originPort + path + " HTTP/1.1\r\n"
                     + "Host: 127.0.0.1:" + originPort + "\r\n"
                     + extraHeaders
                     + "Connection: close\r\n\r\n";
@@ -295,6 +299,32 @@ void errors_logsWithHeadersOnServerError() throws Exception {
         assertThat(logged).contains("X-Custom: visible");
     }
 
+    @Test
+    void errors_staysQuietForSquidsWarmupRequest() throws Exception {
+        // Web sends this through every new tunnel and it fails by design; logged, it printed
+        // two WARNINGs on every start that read as a broken tunnel.
+        startOrigin(502);
+        startProxy("errors", null);
+
+        proxyGet("/squid-internal-tunnel-warmup", "");
+
+        // A deliberate wait, not a guess at readiness: this asserts a record never appears,
+        // so there is nothing to poll for and the only way to be wrong is to look too early.
+        Thread.sleep(200);
+        assertThat(captured.count()).isZero();
+    }
+
+    @Test
+    void url_stillLogsSquidsWarmupRequest() throws Exception {
+        // url asked for every request, so it is not this handler's place to leave one out.
+        startOrigin(502);
+        startProxy("url", null);
+
+        proxyGet("/squid-internal-tunnel-warmup", "");
+
+        assertThat(awaitLogged()).contains("/squid-internal-tunnel-warmup").contains("502");
+    }
+
     @Test
     void reusesAnIncomingCorrelationId() throws Exception {
         // A trace that starts in the test framework should stay joined up through the tunnel.