Tests - Rework how taskw is launched from python

* Should avoid some odd race conditions

test/basetest/utils.py

@@ -13,7 +13,7 @@ try:
     import simplejson as json
 except ImportError:
     import json
-from .exceptions import CommandError, TimeoutWaitingForStream
+from .exceptions import CommandError, TimeoutWaitingFor
 
 USED_PORTS = set()
 ON_POSIX = 'posix' in sys.builtin_module_names
@@ -54,76 +54,140 @@ def binary_location(cmd):
         return os.path.join(BIN_PREFIX, cmd)
 
 
-def wait_process(proc, timeout=1):
-    """Wait for process to finish
+def wait_condition(cond, timeout=1):
+    """Wait for condition to return anything other than None
     """
     if timeout is None:
         timeout = 1
 
     sleeptime = .1
+
+    if timeout < sleeptime:
+        print("Warning, timeout cannot be smaller than", sleeptime)
+        timeout = sleeptime
+
     # Max number of attempts until giving up
     tries = int(timeout / sleeptime)
 
     # Wait for up to a second for the process to finish and avoid zombies
     for i in range(tries):
-        exit = proc.poll()
+        val = cond()
 
-        if exit is not None:
+        if val is not None:
             break
 
         sleep(sleeptime)
 
-    return exit
+    return val
 
 
-def _get_output(proc, input, timeout=None):
+def wait_process(pid, timeout=None):
+    """Wait for process to finish
+    """
+    def process():
+        try:
+            os.kill(pid, 0)
+        except OSError:
+            # Process is dead
+            return True
+        else:
+            # Process is still ticking
+            return None
+
+    return wait_condition(process, timeout)
+
+
+def _queue_output(arguments, pidq, outputq):
+    """Read/Write output/input of given process.
+    This function is meant to be executed in a thread as it may block
+    """
+    kwargs = arguments["process"]
+    input = arguments["input"]
+
+    proc = Popen(**kwargs)
+
+    # NOTE If for whatever reason pid is None at the time of access, use the
+    # following line instead
+    # pid = wait_condition(lambda: proc.pid)
+    pid = proc.pid
+    # Put the PID in the queue for main process to know
+    pidq.put(pid)
+
+    # Send input and wait for finish
+    out, err = proc.communicate(input)
+
+    # Give the output back to the caller
+    outputq.put((out, err, proc.returncode))
+
+
+def _retrieve_output(thread, timeout, queue, thread_error):
+    """Fetch output from taskw subprocess queues
+    """
+    # Try to join the thread on failure abort
+    thread.join(timeout)
+    if thread.isAlive():
+        # Join should have killed the thread. This is unexpected
+        raise TimeoutWaitingFor(thread_error + ". Unexpected error")
+
+    # Thread died so we should have output
+    try:
+        # data = (stdout, stderr, exitcode)
+        data = queue.get(timeout=timeout)
+    except Empty:
+        data = TimeoutWaitingFor("streams from TaskWarrior")
+
+    return data
+
+
+def _get_output(arguments, timeout=None):
     """Collect output from the subprocess without blocking the main process if
     subprocess hangs.
     """
-    def queue_output(proc, input, outq, errq):
-        """Read/Write output/input of given process.
-        This function is meant to be executed in a thread as it may block
-        """
-        # Send input and wait for finish
-        out, err = proc.communicate(input)
-        # Give the output back to the caller
-        outq.put(out)
-        errq.put(err)
+    # NOTE Increase this value if tests fail with None being received as
+    # stdout/stderr instead of the expected content
+    output_timeout = 0.1  # seconds
 
-    outq = Queue()
-    errq = Queue()
+    pidq = Queue()
+    outputq = Queue()
 
-    t = Thread(target=queue_output, args=(proc, input, outq, errq))
+    t = Thread(target=_queue_output, args=(arguments, pidq, outputq))
     t.daemon = True
     t.start()
 
-    # A task process shouldn't take longer than 1 second to finish
-    exit = wait_process(proc, timeout)
+    try:
+        pid = pidq.get(timeout=timeout)
+    except Empty:
+        return _retrieve_output(t, output_timeout, outputq,
+                                "TaskWarrior to start")
 
-    # If it does take longer than 1 second, abort it
-    if exit is None:
+    # Wait for process to finish (normal execution)
+    state = wait_process(pid, timeout)
+
+    if state:
+        # Process finished
+        return _retrieve_output(t, output_timeout, outputq,
+                                "TaskWarrior thread to join")
+
+    # If we reach this point we assume the process got stuck or timed out
+    for sig in (signal.SIGABRT, signal.SIGTERM, signal.SIGKILL):
+        # Start with lower signals and escalate if process ignores them
         try:
-            proc.send_signal(signal.SIGABRT)
+            os.kill(pid, signal.SIGABRT)
         except OSError as e:
             # 3 means the process finished/died between last check and now
             if e.errno != 3:
                 raise
-        exit = wait_process(proc)
 
-    # NOTE Increase this value if tests fail with None being received as
-    # stdout/stderr instead of the expected content
-    timeout = 0.1  # seconds
+        # Wait for process to finish (should die/exit after signal)
+        state = wait_process(pid, timeout)
 
-    try:
-        out = outq.get(timeout=timeout)
-    except Empty:
-        out = TimeoutWaitingForStream("stdout")
-    try:
-        err = errq.get(timeout=timeout)
-    except Empty:
-        err = TimeoutWaitingForStream("stderr")
+        if state:
+            # Process finished
+            return _retrieve_output(t, output_timeout, outputq,
+                                    "TaskWarrior to die")
 
-    return out, err, exit
+    # This should never happen but in case something goes really bad
+    raise OSError("TaskWarrior stopped responding and couldn't be killed")
 
 
 def run_cmd_wait(cmd, input=None, stdout=PIPE, stderr=PIPE,
@@ -140,9 +204,19 @@ def run_cmd_wait(cmd, input=None, stdout=PIPE, stderr=PIPE,
     else:
         stderr = PIPE
 
-    p = Popen(cmd, stdin=stdin, stdout=stdout, stderr=stderr, bufsize=1,
-              close_fds=ON_POSIX, env=env)
-    out, err, exit = _get_output(p, input, timeout)
+    arguments = {
+        "process": {
+            "args": cmd,
+            "stdin": stdin,
+            "stdout": stdout,
+            "stderr": stderr,
+            "bufsize": 1,
+            "close_fds": ON_POSIX,
+            "env": env,
+        },
+        "input": input,
+    }
+    out, err, exit = _get_output(arguments, timeout)
 
     if merge_streams:
         if exit != 0: