added some error messages when using --pid-file

lib/Basics/FileUtils.cpp

@@ -359,6 +359,17 @@ namespace triagens {
       }
       
       
+      off_t size (string const& path) {
+        struct stat stbuf;
+        int res = stat(path.c_str(), &stbuf);
+        if (res != 0) {
+          return 0;
+        }
+
+        return stbuf.st_size;
+      }
+
+
 
       string stripExtension (string const& path, string const& extension) {
         size_t pos = path.rfind(extension);

lib/Basics/FileUtils.h

@@ -130,6 +130,14 @@ namespace triagens {
 
       bool exists (string const& path);
 
+////////////////////////////////////////////////////////////////////////////////
+/// @brief returns the size of a file. will return 0 for non-existing files
+///
+/// the caller should check first if the file exists via the exists() method
+////////////////////////////////////////////////////////////////////////////////
+
+      off_t size (string const& path);
+
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief strip extension
 ////////////////////////////////////////////////////////////////////////////////

lib/Rest/AnyServer.cpp

@@ -68,7 +68,7 @@ static void CheckPidFile (string const& pidFile) {
       TRI_FlushLogging();
       exit(EXIT_FAILURE);
     }
-    else if (FileUtils::exists(pidFile)) {
+    else if (FileUtils::exists(pidFile) && FileUtils::size(pidFile) > 0) {
       LOGGER_INFO << "pid-file '" << pidFile << "' already exists, verifying pid";
 
       ifstream f(pidFile.c_str());
@@ -137,7 +137,7 @@ static void WritePidFile (string const& pidFile, int pid) {
   ofstream out(pidFile.c_str(), ios::trunc);
 
   if (! out) {
-    cerr << "cannot write pid\n";
+    cerr << "cannot write pid-file \"" << pidFile << "\"\n";
     exit(EXIT_FAILURE);
   }
 
@@ -159,6 +159,9 @@ static int forkProcess (string const& pidFile, string const& workingDirectory, s
     exit(EXIT_FAILURE);
   }
 
+  // Upon successful completion, fork() shall return 0 to the child process and 
+  // shall return the process ID of the child process to the parent process.
+
   // if we got a good PID, then we can exit the parent process
   if (pid > 0) {
     LOGGER_DEBUG << "started child process with pid " << pid;