add debug for headers issue (issue #9 on root git)

http-middleware.js

@@ -16,28 +16,70 @@ HttpMiddleware.create = function(gl, defaultApp) {
             explainError(gl, err, "http_01_middleware_socket", hostname);
         });
 
-        if (skipIfNeedBe(req, res, next, defaultApp, hostname)) {
+        // Skip unless the path begins with /.well-known/acme-challenge/
+        if (!hostname || 0 !== req.url.indexOf(challengePrefix)) {
+            skipChallenge(req, res, next, defaultApp);
             return;
         }
 
+        // HEADERS SENT DEBUG NOTE #2
+        // at this point, it's most likely Let's Encrypt server
+        // (or greenlock itself) performing the verification process
+        // Hmmm... perhaps we should change the greenlock prefix to test
+        // Anyway, we just got fast the first place where we could
+        // be sending headers.
+
         var token = req.url.slice(challengePrefix.length);
 
+        var done = false;
+        var countA = 0;
+        var countB = 0;
         gl.getAcmeHttp01ChallengeResponse({ type: "http-01", servername: hostname, token: token })
             .catch(function(err) {
+                countA += 1;
+                // HEADERS SENT DEBUG NOTE #3
+                // This is the second possible time we could be sending headers
                 respondToError(gl, res, err, "http_01_middleware_challenge_response", hostname);
+                done = true;
                 return { __done: true };
             })
             .then(function(result) {
+                countB += 1;
                 if (result && result.__done) {
                     return;
                 }
+                if (done) {
+                    console.error("Sanity check fail: `done` is in a quantum state of both true and false... huh?");
+                    return;
+                }
+                // HEADERS SENT DEBUG NOTE #4b
+                // This is the third/fourth possible time send headers
                 return respondWithGrace(res, result, hostname, token);
+            })
+            .catch(function(err) {
+                // HEADERS SENT DEBUG NOTE #5
+                // I really don't see how this can be possible.
+                // Every case appears to be accounted for
+                console.error();
+                console.error("[warning] Developer Error:" + (err.code || err.context || ""), countA, countB);
+                console.error(err.stack);
+                console.error();
+                console.error(
+                    "This is probably the error that happens routinely on http2 connections, but we're not sure why."
+                );
+                console.error("To track the status or help contribute,");
+                console.error("visit: https://git.rootprojects.org/root/greenlock-express.js/issues/9");
+                console.error();
+                try {
+                    res.end("Internal Server Error [1003]: See logs for details.");
+                } catch (e) {
+                    // ignore
+                }
             });
     };
 };
 
-function skipIfNeedBe(req, res, next, defaultApp, hostname) {
-    if (!hostname || 0 !== req.url.indexOf(challengePrefix)) {
+function skipChallenge(req, res, next, defaultApp) {
     if ("function" === typeof defaultApp) {
         defaultApp(req, res, next);
     } else if ("function" === typeof next) {
@@ -47,10 +89,12 @@ function skipIfNeedBe(req, res, next, defaultApp, hostname) {
         res.end("[500] Developer Error: app.use('/', greenlock.httpMiddleware()) or greenlock.httpMiddleware(app)");
     }
 }
-}
 
 function respondWithGrace(res, result, hostname, token) {
     var keyAuth = result && result.keyAuthorization;
+
+    // HEADERS SENT DEBUG NOTE #4b
+    // This is (still) the third/fourth possible time we could be sending headers
     if (keyAuth && "string" === typeof keyAuth) {
         res.setHeader("Content-Type", "text/plain; charset=utf-8");
         res.end(keyAuth);
@@ -69,14 +113,18 @@ function explainError(gl, err, ctx, hostname) {
     if (!err.context) {
         err.context = ctx;
     }
+    // leaving this in the build for now because it will help with existing error reports
+    console.error("[warning] network connection error:", (err.context || "") + " " + err.message);
     (gl.notify || gl._notify)("error", err);
     return err;
 }
 
 function respondToError(gl, res, err, ctx, hostname) {
+    // HEADERS SENT DEBUG NOTE #3b
+    // This is (still) the second possible time we could be sending headers
     err = explainError(gl, err, ctx, hostname);
     res.statusCode = 500;
-    res.end("Internal Server Error: See logs for details.");
+    res.end("Internal Server Error [1004]: See logs for details.");
 }
 
 HttpMiddleware.getHostname = function(req) {

package.json

@@ -1,6 +1,6 @@
 {
     "name": "@root/greenlock-express",
-    "version": "3.0.15",
+    "version": "3.0.16",
     "description": "Free SSL and managed or automatic HTTPS for node.js with Express, Koa, Connect, Hapi, and all other middleware systems.",
     "main": "greenlock-express.js",
     "homepage": "https://greenlock.domains",

servers.js

@@ -20,12 +20,20 @@ Servers.create = function(greenlock) {
 
     servers.httpServer = function(defaultApp) {
         if (_httpServer) {
+            if (defaultApp) {
+                console.error("error: can only call httpServer(app) once");
+                process.exit(1);
+            }
             return _httpServer;
         }
 
         if (!defaultApp) {
             defaultApp = require("redirect-https")();
         }
+        // HEADERS SENT DEBUG NOTE #1
+        // As seen above, it's only possible to create the server once.
+        // It always gets the http middleware, it always gets a single default app
+        // Therefore it seems impossible to be an http.on('connection', app) problem
         _httpServer = http.createServer(HttpMiddleware.create(greenlock, defaultApp));
         _httpServer.once("error", startError);