Fix worker count to use CPU affinity correctly and be properly bounded

We were using the `cpu_count`, which doesn't respect container affinity. Now, we use `cpu_affinity` and also bound to make sure we don't start a million workers

Fixes https://jira.coreos.com/browse/QUAY-928

util/workers.py

@@ -0,0 +1,31 @@
+import os
+import psutil
+
+def get_worker_count(worker_kind_name, multiplier, minimum=None, maximum=None):
+  """ Returns the number of gunicorn workers to run for the given worker kind,
+      based on a combination of environment variable, multiplier, minimum (if any),
+      and number of accessible CPU cores.
+  """
+  minimum = minimum or multiplier
+  maximum = maximum or (multiplier * multiplier)
+
+  # Check for an override via an environment variable.
+  override_value = os.environ.get('WORKER_COUNT_' + worker_kind_name.upper())
+  if override_value is not None:
+    return max(override_value, minimum)
+
+  override_value = os.environ.get('WORKER_COUNT')
+  if override_value is not None:
+    return max(override_value, minimum)
+
+  # Load the number of CPU cores via affinity, and use that to calculate the
+  # number of workers to run.
+  p = psutil.Process(os.getpid())
+
+  try:
+    cpu_count = len(p.cpu_affinity())
+  except AttributeError:
+    # cpu_affinity isn't supported on this platform. Assume 2.
+    cpu_count = 2
+
+  return  min(max(cpu_count * multiplier, minimum), maximum)