[swarming] Let v8 test driver use gtest environment variables for shards.

tools/run-tests.py

 #!/usr/bin/env python
 #
 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 440 matching lines @@
     return False
   if not CheckTestMode("slow test", options.slow_tests):
     return False
   if not CheckTestMode("pass|fail test", options.pass_fail_tests):
     return False
   if options.no_i18n:
     TEST_MAP["default"].remove("intl")
   return True
 
 
-def ShardTests(tests, shard_count, shard_run):
+def ShardTests(tests, options):
+  # Read gtest shard configuration from environment (e.g. set by swarming).
+  # If none is present, use values passed on the command line.
+  shard_count = int(os.environ.get('GTEST_TOTAL_SHARDS', options.shard_count))
+  shard_run = os.environ.get('GTEST_SHARD_INDEX')
+  if shard_run is not None:
+    # The v8 shard_run starts at 1, while GTEST_SHARD_INDEX starts at 0.
+    shard_run = int(shard_run) + 1
+  else:
+    shard_run = options.shard_run
+
+  if options.shard_count > 1:
+    # Log if a value was passed on the cmd line and it differs from the
+    # environment variables.
+    if options.shard_count != shard_count:
+      print("shard_count from cmd line differs from environment variable "
+            "GTEST_TOTAL_SHARDS")
+    if options.shard_run > 1 and options.shard_run != shard_run:
+      print("shard_run from cmd line differs from environment variable "
+            "GTEST_SHARD_INDEX")
+
   if shard_count < 2:
     return tests
   if shard_run < 1 or shard_run > shard_count:
     print "shard-run not a valid number, should be in [1:shard-count]"
     print "defaulting back to running all tests"
     return tests
   count = 0
   shard = []
   for test in tests:
     if count % shard_count == shard_run - 1:
@@ skipping 171 matching lines @@
           else:
             yield ["--random-seed=%d" % RandomSeed()]
       s.tests = [
         t.CopyAddingFlags(t.variant, flags)
         for t in variant_tests
         for flags in iter_seed_flags()
       ]
     else:
       s.tests = variant_tests
 
-    s.tests = ShardTests(s.tests, options.shard_count, options.shard_run)
+    s.tests = ShardTests(s.tests, options)
     num_tests += len(s.tests)
 
   if options.cat:
     return 0  # We're done here.
 
   if options.report:
     verbose.PrintReport(all_tests)
 
   # Run the tests, either locally or distributed on the network.
   start_time = time.time()
@@ skipping 40 matching lines @@
     verbose.PrintTestDurations(suites, overall_duration)
 
   if num_tests == 0:
     print("Warning: no tests were run!")
 
   return exit_code
 
 
 if __name__ == "__main__":
   sys.exit(Main())