Make test_event more reliable

Look for the expected message several times, with short sleeps in
between. That way we will not sleep more than necessary, yet will
not immediately give up either.

server/core/test/test_event.cc

@@ -481,26 +481,41 @@ int test_logging()
 
     MXS_LOG_EVENT(event::AUTHENTICATION_FAILURE, "%s", id.c_str());
 
-    // Short sleep to increase the likelyhood that the logged message ends
-    // ends up where we expect it to be.
-    sleep(2);
+    // We have no control over how quickly syslog messages are flushed
+    // to the file. So, we try a few times before giving up.
 
     bool found = false;
+    int attempts = 0;
+    const int MAX_ATTEMPTS = 10;
 
-    ifstream in("/var/log/auth.log");
-
-    if (in)
+    do
     {
-        string line;
-        while (std::getline(in, line))
+        ++attempts;
+
+        sleep(1);
+
+        const char* zName = "/var/log/auth.log";
+        ifstream in(zName);
+
+        if (in)
         {
-            if (line.find(id) != string::npos)
+            string line;
+            while (std::getline(in, line))
             {
-                found = true;
-                cout << "notice: Found '" << id << "' in line '" << line << "'." << endl;
+                if (line.find(id) != string::npos)
+                {
+                    found = true;
+                    cout << "notice: Found '" << id << "' in line '" << line << "'." << endl;
+                }
             }
         }
+        else
+        {
+            cerr << "error: Could not open '" << zName << "'." << endl;
+            attempts = MAX_ATTEMPTS;
+        }
     }
+    while (!found && (attempts < MAX_ATTEMPTS));
 
     return found ? 0 : 1;
 }