Issue 7019 - [CMS] Refactor `test_server.py`

tests/utils.py

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 import contextlib
 import os
 import signal
 import subprocess
 import time
 import zipfile
 from io import BytesIO
+import urllib2
+import traceback
 
 import pytest
 
 
 def get_dir_contents(path):
     # TODO: This function is duplicated in test_page_outputs.py.
     dirdata = {}
     for dirpath, dirnames, filenames in os.walk(path):
         for output_file in filenames:
             filepath = os.path.join(dirpath, output_file)
             with open(filepath) as f:
                 locale = os.path.split(os.path.split(filepath)[0])[1]
                 dirdata[os.path.join(locale, output_file)] = f.read().strip()
     return dirdata
 
 
 @contextlib.contextmanager
-def run_test_server(site_path):
+def run_test_server(site_path, new_env=None):
     """Run test server, yield its URL. Terminate server on next iteration.
 
     This function is intended be used in a pytest fixture.
+
+    Parameters
+    ----------
+    site_path: str
+        The path to the website's source code.
+    new_env: dict
+        The environment under which the server will be run. If `None`, this
+        will be inherited from the main process.
+
+    Returns
+    -------
+    str
+        The url where the server runs.
+
     """
     args = ['python', 'runserver.py', site_path]
     # Werkzeug is a dependency of flask which we are using for the mock api
     # however there is an issue with Werkzeug that prevents it from properly
     # handling the SIGTERM sent by p.kill() or terminate()
     # Issue: https://github.com/pallets/werkzeug/issues/58
-    p = subprocess.Popen(args, stdout=subprocess.PIPE, preexec_fn=os.setsid)
-    time.sleep(0.5)
+    p = subprocess.Popen(args, stdout=subprocess.PIPE, preexec_fn=os.setsid,
+                         env=new_env)
+    works, err = _test_server_and_wait()
+    if not works:
+        os.killpg(os.getpgid(p.pid), signal.SIGINT)

[Vasily Kuznetsov, 2018/10/25 15:51:43]

We can get rid of the replication of this line using a try/finally block. Like
this:

try:
    _wait_for_server()
    yield 'http://.....'
finally:
    os.killpg(...)

and then _wait_for_server() would just reraise the exception once the timeout is
expired: I don't think the fancy handling adds that much value here.

[Tudor Avram, 2018/10/29 10:42:51]

Done.

+        raise Exception('Could not get the server running on `http://localhost'
+                        ':5000/`. See traceback:\n{}'.format(err))
     yield 'http://localhost:5000/'
-    os.killpg(os.getpgid(p.pid), signal.SIGTERM)
+    os.killpg(os.getpgid(p.pid), signal.SIGINT)
+
+
+def _test_server_and_wait():
+    """Test the server started by `run_test_server` and fail after 2s.
+
+    Expects the server to be active at `http://localhost:5000/`.
+
+    Returns
+    -------
+    bool
+        True - if the server works as expected
+        False - otherwise
+    str or None
+        The traceback of the error - if the server connection fails
+        None - otherwise
+
+    Raises
+    ------
+    Exception
+        If the server is not running after retry-ing for 2 seconds.
+
+    """
+    start_time = time.time()
+
+    while True:
+        try:
+            urllib2.urlopen('http://localhost:5000/')
+            return True, None
+        except Exception:
+            time.sleep(.1)
+            if time.time() - start_time > 2:
+                return False, traceback.format_exc()
 
 
 def create_in_memory_zip(file_names, file_data):
     """Create a BytesIO object with the contents of a zip file.
 
     Parameters
     ----------
     file_names: iterable
         Of file names. Should be the full paths of the file inside the zip.
     file_data: iterable
@@ skipping 13 matching lines @@
 
     memory_zip.seek(0)
     return memory_zip
 
 
 def exception_test(func, exception, exp_msg, *args, **kw):
     with pytest.raises(exception) as err:
         func(*args, **kw)
 
     assert exp_msg in str(err.value)