Fix HBPVIS#224: Handle exceptions in server handlers

tests/http/server.cpp

@@ -79,6 +79,10 @@ const Response response204{ServerReponse::no_content, ""};
 const Response error400{ServerReponse::bad_request, ""};
 const Response error404{ServerReponse::not_found, ""};
 const Response error405{ServerReponse::method_not_allowed, ""};
+Response error500(const std::string& body)
+{
+    return Response(ServerReponse::internal_server_error, body);
+}
 
 const std::string jsonGet("Not JSON, just want to see that the is data a-ok");
 const std::string jsonPut("See what my stepbrother jsonGet says");
@@ -977,6 +981,30 @@ BOOST_AUTO_TEST_CASE(issue157)
     thread.join();
 }
 
+BOOST_AUTO_TEST_CASE(issue224) // robustness when handlers throw
+{
+    bool running = true;
+    zeroeq::http::Server server;
+
+    server.handleGET("test/foo", [&]() {
+        throw std::runtime_error("I've had enough!");
+        return jsonGet;
+    });
+
+    std::thread thread([&]() {
+        while (running)
+            server.receive(TIMEOUT);
+    });
+
+    Client client(server.getURI());
+    client.checkGET("/test/foo",
+                    error500("Request handler exception: I've had enough!"),
+                    __LINE__);
+
+    running = false;
+    thread.join();
+}
+
 BOOST_AUTO_TEST_CASE(urlcasesensitivity)
 {
     bool running = true;

zeroeq/http/server.cpp

@@ -659,7 +659,23 @@ bool Server::process(detail::Socket&)
     }
     else
     {
-        message->response = respondTo(message->request);
+        try
+        {
+            message->response = respondTo(message->request);
+        }
+        catch (const std::exception& e)
+        {
+            message->response =
+                make_ready_response(Code::INTERNAL_SERVER_ERROR,
+                                    std::string("Request handler exception: ") +
+                                        e.what());
+        }
+        catch (...)
+        {
+            message->response =
+                make_ready_response(Code::INTERNAL_SERVER_ERROR,
+                                    "An unknown exception occured");
+        }
 
         // When a client makes a CORS request (by setting an 'Origin' header) it
         // expects an 'Access-Control-Allow-Origin' response header. See: