Add COMPOSE_PARALLEL_LIMIT to restrict global number of parallel operations

Signed-off-by: Shea Rozmiarek <uberpanzermensch@gmail.com>

1 files changed, 15 insertions, 1 deletions

diff --git a/compose/parallel.py b/compose/parallel.py
index f271561f..4f881c8f 100644
--- a/compose/parallel.py
+++ b/compose/parallel.py
@@ -15,6 +15,8 @@ from six.moves.queue import Queue
 from compose.cli.colors import green
 from compose.cli.colors import red
 from compose.cli.signals import ShutdownException
+from compose.config.environment import Environment
+from compose.const import PARALLEL_LIMIT
 from compose.errors import HealthCheckFailed
 from compose.errors import NoHealthCheckConfigured
 from compose.errors import OperationFailedError
@@ -26,6 +28,18 @@ log = logging.getLogger(__name__)
 STOP = object()
 
 
+def get_configured_limit():
+    limit = Environment.from_command_line({'COMPOSE_PARALLEL_LIMIT': None})['COMPOSE_PARALLEL_LIMIT']
+    if limit:
+        limit = int(limit)
+    else:
+        limit = PARALLEL_LIMIT
+    return limit
+
+
+global_limiter = Semaphore(get_configured_limit())
+
+
 def parallel_execute(objects, func, get_name, msg, get_deps=None, limit=None, parent_objects=None):
     """Runs func on objects in parallel while ensuring that func is
     ran on object only after it is ran on all its dependencies.
@@ -173,7 +187,7 @@ def producer(obj, func, results, limiter):
     The entry point for a producer thread which runs func on a single object.
     Places a tuple on the results queue once func has either returned or raised.
     """
-    with limiter:
+    with limiter, global_limiter:
         try:
             result = func(obj)
             results.put((obj, result, None))