The linux_chromium_asan_rel_ng trybot is failing many tryjobs while running net_unittests due to the following failure after shards complete successfully:

16792 2016-04-12 02:17:09.658 E: Unable to open given url, https://isolateserver.appspot.com/_ah/api/isolateservice/v1/preupload, after 30 attempts.
HTTPSConnectionPool(host='isolateserver.appspot.com', port=443): Max retries exceeded with url: /_ah/api/isolateservice/v1/preupload (Caused by NewConnectionError('<third_party.requests.packages.urllib3.connection.VerifiedHTTPSConnection object at 0x36669d0>: Failed to establish a new connection: [Errno 101] Network is unreachable',))
16792 2016-04-12 02:17:09.665 E: Leaking out_dir /tmp/outdSTiKa: Failed to execute preupload query
Traceback (most recent call last):
  File "/b/swarm_slave/swarming_bot.1.zip/client/run_isolated.py", line 402, in map_and_run
    storage, out_dir, leak_temp_dir)
  File "/b/swarm_slave/swarming_bot.1.zip/client/run_isolated.py", line 248, in delete_and_upload
    storage, [out_dir], None)
  File "/b/swarm_slave/swarming_bot.1.zip/client/isolateserver.py", line 2050, in archive_files_to_storage
    uploaded = storage.upload_items(items_to_upload)
  File "/b/swarm_slave/swarming_bot.1.zip/client/isolateserver.py", line 449, in upload_items
    for missing_item, push_state in self.get_missing_items(items):
  File "/b/swarm_slave/swarming_bot.1.zip/client/isolateserver.py", line 628, in get_missing_items
    for missing_item, push_state in channel.pull().iteritems():
  File "/b/swarm_slave/swarming_bot.1.zip/utils/threading_utils.py", line 377, in _task_executer
    result = func(*args, **kwargs)
  File "/b/swarm_slave/swarming_bot.1.zip/client/isolateserver.py", line 618, in contains
    return self._storage_api.contains(batch)
  File "/b/swarm_slave/swarming_bot.1.zip/client/isolateserver.py", line 1112, in contains
    'Failed to execute preupload query')
MappingError: Failed to execute preupload query


Example failures of this nature:

https://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_asan_rel_ng/builds/144311
https://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_asan_rel_ng/builds/144306
https://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_asan_rel_ng/builds/144305
https://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_asan_rel_ng/builds/144303
https://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_asan_rel_ng/builds/144297
https://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_asan_rel_ng/builds/144295
https://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_asan_rel_ng/builds/144292
https://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_asan_rel_ng/builds/144290

https://chromium-swarm.appspot.com/user/task/2e21d81d25e9be10
https://chromium-swarm.appspot.com/user/task/2e21d81f6de79310
https://chromium-swarm.appspot.com/user/task/2e21d822bd1b8e10
https://chromium-swarm.appspot.com/user/task/2e21d823ffb67810

Marking P0. Requires immediate attention as it's blocking CQ jobs.