Merge pull request #3291 from aanand/parallel-execute-refactor

Parallel execution refactor/fixes

compose/parallel.py

@@ -1,6 +1,7 @@
 from __future__ import absolute_import
 from __future__ import unicode_literals
 
+import logging
 import operator
 import sys
 from threading import Thread
@@ -14,6 +15,9 @@ from compose.cli.signals import ShutdownException
 from compose.utils import get_output_stream
 
 
+log = logging.getLogger(__name__)
+
+
 def parallel_execute(objects, func, get_name, msg, get_deps=None):
     """Runs func on objects in parallel while ensuring that func is
     ran on object only after it is ran on all its dependencies.
@@ -28,32 +32,24 @@ def parallel_execute(objects, func, get_name, msg, get_deps=None):
     for obj in objects:
         writer.initialize(get_name(obj))
 
-    q = setup_queue(objects, func, get_deps, get_name)
+    events = parallel_execute_stream(objects, func, get_deps)
 
-    done = 0
     errors = {}
     results = []
     error_to_reraise = None
 
-    while done < len(objects):
-        try:
-            obj, result, exception = q.get(timeout=1)
-        except Empty:
-            continue
-        # See https://github.com/docker/compose/issues/189
-        except thread.error:
-            raise ShutdownException()
-
+    for obj, result, exception in events:
         if exception is None:
             writer.write(get_name(obj), 'done')
             results.append(result)
         elif isinstance(exception, APIError):
             errors[get_name(obj)] = exception.explanation
             writer.write(get_name(obj), 'error')
+        elif isinstance(exception, UpstreamError):
+            writer.write(get_name(obj), 'error')
         else:
             errors[get_name(obj)] = exception
             error_to_reraise = exception
-        done += 1
 
     for obj_name, error in errors.items():
         stream.write("\nERROR: for {}  {}\n".format(obj_name, error))
@@ -68,40 +64,83 @@ def _no_deps(x):
     return []
 
 
-def setup_queue(objects, func, get_deps, get_name):
+class State(object):
+    def __init__(self, objects):
+        self.objects = objects
+
+        self.started = set()   # objects being processed
+        self.finished = set()  # objects which have been processed
+        self.failed = set()    # objects which either failed or whose dependencies failed
+
+    def is_done(self):
+        return len(self.finished) + len(self.failed) >= len(self.objects)
+
+    def pending(self):
+        return set(self.objects) - self.started - self.finished - self.failed
+
+
+def parallel_execute_stream(objects, func, get_deps):
     if get_deps is None:
         get_deps = _no_deps
 
     results = Queue()
-    started = set()   # objects being processed
-    finished = set()  # objects which have been processed
+    state = State(objects)
+
+    while not state.is_done():
+        for event in feed_queue(objects, func, get_deps, results, state):
+            yield event
 
-    def do_op(obj):
         try:
-            result = func(obj)
-            results.put((obj, result, None))
-        except Exception as e:
-            results.put((obj, None, e))
-
-        finished.add(obj)
-        feed()
-
-    def ready(obj):
-        # Is object ready for performing operation
-        return obj not in started and all(
-            dep not in objects or dep in finished
-            for dep in get_deps(obj)
-        )
-
-    def feed():
-        for obj in filter(ready, objects):
-            started.add(obj)
-            t = Thread(target=do_op, args=(obj,))
+            event = results.get(timeout=0.1)
+        except Empty:
+            continue
+        # See https://github.com/docker/compose/issues/189
+        except thread.error:
+            raise ShutdownException()
+
+        obj, _, exception = event
+        if exception is None:
+            log.debug('Finished processing: {}'.format(obj))
+            state.finished.add(obj)
+        else:
+            log.debug('Failed: {}'.format(obj))
+            state.failed.add(obj)
+
+        yield event
+
+
+def queue_producer(obj, func, results):
+    try:
+        result = func(obj)
+        results.put((obj, result, None))
+    except Exception as e:
+        results.put((obj, None, e))
+
+
+def feed_queue(objects, func, get_deps, results, state):
+    pending = state.pending()
+    log.debug('Pending: {}'.format(pending))
+
+    for obj in pending:
+        deps = get_deps(obj)
+
+        if any(dep in state.failed for dep in deps):
+            log.debug('{} has upstream errors - not processing'.format(obj))
+            yield (obj, None, UpstreamError())
+            state.failed.add(obj)
+        elif all(
+            dep not in objects or dep in state.finished
+            for dep in deps
+        ):
+            log.debug('Starting producer thread for {}'.format(obj))
+            t = Thread(target=queue_producer, args=(obj, func, results))
             t.daemon = True
             t.start()
+            state.started.add(obj)
 
-    feed()
-    return results
+
+class UpstreamError(Exception):
+    pass
 
 
 class ParallelStreamWriter(object):

compose/service.py

@@ -135,6 +135,9 @@ class Service(object):
         self.networks = networks or {}
         self.options = options
 
+    def __repr__(self):
+        return '<Service: {}>'.format(self.name)
+
     def containers(self, stopped=False, one_off=False, filters={}):
         filters.update({'label': self.labels(one_off=one_off)})
 

tests/unit/parallel_test.py

@@ -0,0 +1,90 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+import six
+from docker.errors import APIError
+
+from compose.parallel import parallel_execute
+from compose.parallel import parallel_execute_stream
+from compose.parallel import UpstreamError
+
+
+web = 'web'
+db = 'db'
+data_volume = 'data_volume'
+cache = 'cache'
+
+objects = [web, db, data_volume, cache]
+
+deps = {
+    web: [db, cache],
+    db: [data_volume],
+    data_volume: [],
+    cache: [],
+}
+
+
+def get_deps(obj):
+    return deps[obj]
+
+
+def test_parallel_execute():
+    results = parallel_execute(
+        objects=[1, 2, 3, 4, 5],
+        func=lambda x: x * 2,
+        get_name=six.text_type,
+        msg="Doubling",
+    )
+
+    assert sorted(results) == [2, 4, 6, 8, 10]
+
+
+def test_parallel_execute_with_deps():
+    log = []
+
+    def process(x):
+        log.append(x)
+
+    parallel_execute(
+        objects=objects,
+        func=process,
+        get_name=lambda obj: obj,
+        msg="Processing",
+        get_deps=get_deps,
+    )
+
+    assert sorted(log) == sorted(objects)
+
+    assert log.index(data_volume) < log.index(db)
+    assert log.index(db) < log.index(web)
+    assert log.index(cache) < log.index(web)
+
+
+def test_parallel_execute_with_upstream_errors():
+    log = []
+
+    def process(x):
+        if x is data_volume:
+            raise APIError(None, None, "Something went wrong")
+        log.append(x)
+
+    parallel_execute(
+        objects=objects,
+        func=process,
+        get_name=lambda obj: obj,
+        msg="Processing",
+        get_deps=get_deps,
+    )
+
+    assert log == [cache]
+
+    events = [
+        (obj, result, type(exception))
+        for obj, result, exception
+        in parallel_execute_stream(objects, process, get_deps)
+    ]
+
+    assert (cache, None, type(None)) in events
+    assert (data_volume, None, APIError) in events
+    assert (db, None, UpstreamError) in events
+    assert (web, None, UpstreamError) in events