Truncate huge output snippets in the test launcher before printing them

base/test/launcher/test_launcher.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/test/launcher/test_launcher.h"
 
 #if defined(OS_POSIX)
 #include <fcntl.h>
 #endif
 
@@ skipping 58 matching lines @@
 // Maximum time of no output after which we print list of processes still
 // running. This deliberately doesn't use TestTimeouts (which is otherwise
 // a recommended solution), because they can be increased. This would defeat
 // the purpose of this timeout, which is 1) to avoid buildbot "no output for
 // X seconds" timeout killing the process 2) help communicate status of
 // the test launcher to people looking at the output (no output for a long
 // time is mysterious and gives no info about what is happening) 3) help
 // debugging in case the process hangs anyway.
 const int kOutputTimeoutSeconds = 15;
 
+// Limit of output snippet lines when printing to stdout.
+// Avoids flooding the logs with amount of output that gums up
+// the infrastructure.
+const size_t kOutputSnippetLinesLimit = 50;
+
 // Set of live launch test processes with corresponding lock (it is allowed
 // for callers to launch processes on different threads).
 LazyInstance<std::map<ProcessHandle, CommandLine> > g_live_processes
     = LAZY_INSTANCE_INITIALIZER;
 LazyInstance<Lock> g_live_processes_lock = LAZY_INSTANCE_INITIALIZER;
 
 #if defined(OS_POSIX)
 // Self-pipe that makes it possible to do complex shutdown handling
 // outside of the signal handler.
 int g_shutdown_pipe[2] = { -1, -1 };
@@ skipping 355 matching lines @@
     print_snippet = (result.status != TestResult::TEST_SUCCESS);
   } else if (print_test_stdio == "always") {
     print_snippet = true;
   } else if (print_test_stdio == "never") {
     print_snippet = false;
   } else {
     LOG(WARNING) << "Invalid value of " << switches::kTestLauncherPrintTestStdio
                  << ": " << print_test_stdio;
   }
   if (print_snippet) {
-    fprintf(stdout, "%s", result.output_snippet.c_str());
+    std::vector<std::string> snippet_lines;

[sky, 2014/06/10 16:25:14]

This initially confused me. I would have thought you wanted the first 50 lines,
but rather you're showing the last. How about a comment?

+    SplitString(result.output_snippet, '\n', &snippet_lines);
+    if (snippet_lines.size() > kOutputSnippetLinesLimit) {
+      size_t truncated_size = snippet_lines.size() - kOutputSnippetLinesLimit;
+      snippet_lines.erase(
+          snippet_lines.begin(),
+          snippet_lines.begin() + truncated_size);
+      snippet_lines.insert(snippet_lines.begin(), "<truncated>");
+    }
+    fprintf(stdout, "%s", JoinString(snippet_lines, "\n").c_str());
     fflush(stdout);
   }
 
   if (result.status == TestResult::TEST_SUCCESS) {
     ++test_success_count_;
   } else {
     tests_to_retry_.insert(result.full_name);
   }
 
   // TODO(phajdan.jr): Flag unreliable unknown results, unless passed on retry.
@@ skipping 608 matching lines @@
 
     g_live_processes.Get().erase(process_handle);
   }
 
   base::CloseProcessHandle(process_handle);
 
   return exit_code;
 }
 
 }  // namespace base