[core] refactor test server startup

test/fixtures/util.cpp

@@ -15,7 +15,6 @@ namespace mbgl {
 namespace test {
 
 pid_t startServer(const char *executable) {
-    const std::string parent_pid = std::to_string(getpid());
     int pipefd[2];
 
     if (pipe(pipefd)) {
@@ -24,19 +23,17 @@ pid_t startServer(const char *executable) {
 
     pid_t pid = fork();
     if (pid < 0) {
-        throw std::runtime_error("Cannot create server process");
+        Log::Error(Event::Setup, "Cannot create server process");
+        exit(1);
     } else if (pid == 0) {
-        close(STDIN_FILENO);
-
-        if (dup(pipefd[1])) {
-            Log::Error(Event::Setup, "Failed to start server: %s", strerror(errno));
-        }
+        // This is the child process.
 
+        // Close the input side of the pipe.
         close(pipefd[0]);
-        close(pipefd[1]);
 
+        // Launch the actual server process, with the pipe ID as the first argument.
         char *args[] = { const_cast<char *>(executable),
-                         const_cast<char *>(parent_pid.c_str()),
+                         const_cast<char *>(std::to_string(pipefd[1]).c_str()),
                          nullptr };
         int ret = execv(executable, args);
         // This call should not return. In case execve failed, we exit anyway.
@@ -45,15 +42,26 @@ pid_t startServer(const char *executable) {
         }
         exit(0);
     } else {
-        char buffer[8];
+        // This is the parent process.
 
-        // Wait until the server process sends something on the pipe.
-        if (!read(pipefd[0], buffer, sizeof(buffer))) {
-            throw std::runtime_error("Error reading a message from the server");
-        }
+        // Close output side of the pipe.
+        close(pipefd[1]);
 
+        // Wait until the server process closes the handle.
+        char buffer[2];
+        ssize_t bytes = 0, total = 0;
+        while ((bytes = read(pipefd[0], buffer, sizeof(buffer))) != 0) {
+            total += bytes;
+        }
+        if (bytes < 0) {
+            Log::Error(Event::Setup, "Failed to start server: %s", strerror(errno));
+            exit(1);
+        }
+        if (total != 2 || strncmp(buffer, "OK", 2) != 0) {
+            Log::Error(Event::Setup, "Failed to start server");
+            exit(1);
+        }
         close(pipefd[0]);
-        close(pipefd[1]);
     }
     return pid;
 }

test/storage/server.js

@@ -2,6 +2,7 @@
 /* jshint node: true */
 'use strict';
 
+var fs = require('fs');
 var express = require('express');
 var app = express();
 
@@ -106,6 +107,7 @@ var server = app.listen(3000, function () {
 
     if (process.argv[2]) {
         // Allow the test to continue running.
-        process.stdin.write("Go!\n");
+        fs.write(+process.argv[2], 'OK');
+        fs.close(+process.argv[2]);
     }
 });