[Fuchsia] Add 'pm serve' liveness check to runner scripts.

Changes the runner script to block script execution and generate log
spam until it has positive confirmation the "pm serve" is serving
HTTP traffic.

"pm serve" is now started immediately after the repo is created, allowing
it to bind its socket in parallel with "pm publish" operations.


Bug: 973754
Change-Id: I92730010524a646204ead8fb8b113968b4179b5a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1659594
Auto-Submit: Kevin Marshall <kmarshall@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#669122}

build/fuchsia/target.py

@@ -11,6 +11,7 @@ import remote_cmd
 import shutil
 import subprocess
 import sys
+import urllib2
 import tempfile
 import time
 
@@ -26,6 +27,9 @@ _REPO_NAME = 'chrome_runner'
 # mitigation against hangs due to amber/network-related failures.
 _INSTALL_TIMEOUT_SECS = 5 * 60
 
+# Maximum amount of time to block while waitin for "pm serve" to come up.
+_PM_SERVE_LIVENESS_TIMEOUT_SECS = 10
+
 
 def _GetPackageInfo(package_path):
   """Returns a tuple with the name and version of a package."""
@@ -57,6 +61,22 @@ class _MapRemoteDataPathForPackage:
       return self.data_path + path[5:]
     return path
 
+def _WaitForPmServeToBeReady(port):
+  """Blocks until "pm serve" starts serving HTTP traffic at |port|."""
+
+  timeout = time.time() + _PM_SERVE_LIVENESS_TIMEOUT_SECS
+  while True:
+    try:
+      urllib2.urlopen('http://localhost:%d' % port, timeout=1).read()
+      break
+    except urllib2.URLError:
+      logging.info('Waiting until \'pm serve\' is up...')
+
+    if time.time() >= timeout:
+      raise Exception('Timed out while waiting for \'pm serve\'.')
+
+    time.sleep(1)
+
 
 class FuchsiaTargetException(Exception):
   def __init__(self, message):
@@ -240,7 +260,6 @@ class Target(object):
       return 'x86_64'
     raise Exception('Unknown target_cpu %s:' % self._target_cpu)
 
-
   def InstallPackage(self, package_path, package_name, package_deps):
     """Installs a package and it's dependencies on the device. If the package is
     already installed then it will be updated to the new version.
@@ -254,11 +273,7 @@ class Target(object):
       tuf_root = tempfile.mkdtemp()
       pm_serve_task = None
 
-      # Publish all packages to the serving TUF repository under |tuf_root|.
       subprocess.check_call([_PM, 'newrepo', '-repo', tuf_root])
-      all_packages = [package_path] + package_deps
-      for next_package_path in all_packages:
-        _PublishPackage(tuf_root, next_package_path)
 
       # Serve the |tuf_root| using 'pm serve' and configure the target to pull
       # from it.
@@ -266,6 +281,14 @@ class Target(object):
       pm_serve_task = subprocess.Popen(
           [_PM, 'serve', '-d', os.path.join(tuf_root, 'repository'), '-l',
            ':%d' % serve_port, '-q'])
+
+      # Publish all packages to the serving TUF repository under |tuf_root|.
+      all_packages = [package_path] + package_deps
+      for next_package_path in all_packages:
+        _PublishPackage(tuf_root, next_package_path)
+
+      _WaitForPmServeToBeReady(serve_port)
+
       remote_port = common.ConnectPortForwardingTask(self, serve_port, 0)
       self._RegisterAmberRepository(tuf_root, remote_port)