cloud_tests: emit dots on Travis while fetching images (#347)

This ensures that Travis will not kill our tests if fetching images is
taking a long time.

In implementation terms, this introduces a context manager which will
spin up a multiprocessing.Process in the background and print a dot to
stdout every 10 seconds.  The process is terminated when the context
manager exits.

This also drop the use of travis_wait, which was being used to work
around this issue.

2 files changed, 36 insertions, 1 deletions

diff --git a/tests/cloud_tests/platforms/__init__.py b/tests/cloud_tests/platforms/__init__.py
index 6a410b84..e506baa0 100644
--- a/tests/cloud_tests/platforms/__init__.py
+++ b/tests/cloud_tests/platforms/__init__.py
@@ -6,6 +6,7 @@ from .ec2 import platform as ec2
 from .lxd import platform as lxd
 from .nocloudkvm import platform as nocloudkvm
 from .azurecloud import platform as azurecloud
+from ..util import emit_dots_on_travis
 
 PLATFORMS = {
     'ec2': ec2.EC2Platform,
@@ -17,7 +18,8 @@ PLATFORMS = {
 
 def get_image(platform, config):
     """Get image from platform object using os_name."""
-    return platform.get_image(config)
+    with emit_dots_on_travis():
+        return platform.get_image(config)
 
 
 def get_instance(snapshot, *args, **kwargs):
diff --git a/tests/cloud_tests/util.py b/tests/cloud_tests/util.py
index 06f7d865..e65771b1 100644
--- a/tests/cloud_tests/util.py
+++ b/tests/cloud_tests/util.py
@@ -5,6 +5,7 @@
 import base64
 import copy
 import glob
+import multiprocessing
 import os
 import random
 import shlex
@@ -12,7 +13,9 @@ import shutil
 import string
 import subprocess
 import tempfile
+import time
 import yaml
+from contextlib import contextmanager
 
 from cloudinit import util as c_util
 from tests.cloud_tests import LOG
@@ -118,6 +121,36 @@ def current_verbosity():
     return max(min(3 - int(LOG.level / 10), 2), 0)
 
 
+@contextmanager
+def emit_dots_on_travis():
+    """
+    A context manager that emits a dot every 10 seconds if running on Travis.
+
+    Travis will kill jobs that don't emit output for a certain amount of time.
+    This context manager spins up a background process which will emit a dot to
+    stdout every 10 seconds to avoid being killed.
+
+    It should be wrapped selectively around operations that are known to take a
+    long time.
+    """
+    if os.environ.get('TRAVIS') != "true":
+        # If we aren't on Travis, don't do anything.
+        yield
+        return
+
+    def emit_dots():
+        while True:
+            print(".")
+            time.sleep(10)
+
+    dot_process = multiprocessing.Process(target=emit_dots)
+    dot_process.start()
+    try:
+        yield
+    finally:
+        dot_process.terminate()
+
+
 def is_writable_dir(path):
     """Make sure dir is writable.