Added a minimalistic init process that will wait for all processes

This should allow running LOCAL workers under Docker, since they won't be
killed right when beekeeper ends

docker/Dockerfile

@@ -32,4 +32,5 @@ ENV EHIVE_ROOT_DIR "/repo/ensembl-hive"
 ENV PATH "/repo/ensembl-hive/scripts:$PATH"
 ENV PERL5LIB "/repo/ensembl-hive/modules:$PERL5LIB"
 
+ENTRYPOINT [ "/repo/ensembl-hive/scripts/dev/simple_init.py" ]
 CMD [ "/bin/bash" ]

scripts/dev/simple_init.py

+#!/usr/bin/env python3
+# Copyright [1999-2015] Wellcome Trust Sanger Institute and the EMBL-European Bioinformatics Institute
+# Copyright [2016-2017] EMBL-European Bioinformatics Institute
+# 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+# 
+#      http://www.apache.org/licenses/LICENSE-2.0
+# 
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+import errno
+import os
+import subprocess
+import sys
+
+
+def wait_for_all_processes():
+    child_errors = False
+    while True:
+        try:
+            # Wait for any child
+            child_pid, child_status = os.waitpid(-1, 0)
+            #print("ripped a child", child_pid, child_status)
+            # Check its status
+            if child_status != 0:
+                child_errors = True
+        except OSError as e:
+            if e.errno == errno.ECHILD:
+                # No more child found
+                return child_errors
+            else:
+                # Other errors
+                raise
+
+
+
+# Run the command
+print("Executing", sys.argv[1:])
+cmd_ret = subprocess.call( sys.argv[1:] )
+
+# Wait for all the processes to end
+child_errors = wait_for_all_processes()
+
+# Return an approriate exit code
+if cmd_ret == 0:
+    cmd_ret = 1 if child_errors else 0
+sys.exit(cmd_ret)
+