Add config for sysctl

Allows the administrator to set custom sysctls on the storage
nodes. This is especially useful for setting kernel.pid_max.

Change-Id: Id902f799796a121578eba10de22e0eb9cc627b9d
Closes-bug: 1396613

config.yaml

@@ -141,3 +141,9 @@ options:
     description: |
       Apply system hardening. Supports a space-delimited list of modules
       to run. Supported modules currently include os, ssh, apache and mysql.
+  sysctl:
+    type: string
+    default:
+    description: |
+      YAML formatted associative array of sysctl values, e.g.:
+      '{ kernel.pid_max : 4194303 }'

hooks/swift_storage_hooks.py

@@ -59,6 +59,9 @@ from charmhelpers.core.host import (
     add_to_updatedb_prunepath,
     rsync,
 )
+
+from charmhelpers.core.sysctl import create as create_sysctl
+
 from charmhelpers.payload.execd import execd_preinstall
 
 from charmhelpers.contrib.openstack.utils import (
@@ -122,6 +125,11 @@ def config_changed():
     save_script_rc()
     if relations_of_type('nrpe-external-master'):
         update_nrpe_config()
+
+    sysctl_dict = config('sysctl')
+    if sysctl_dict:
+        create_sysctl(sysctl_dict, '/etc/sysctl.d/50-swift-storage-charm.conf')
+
     add_to_updatedb_prunepath(STORAGE_MOUNT_PATH)