Allow the getval task to work with customized hostnames

tasks/getval.json

@@ -3,6 +3,10 @@
     "input_method": "stdin",
     "files": ["python_task_helper/files/task_helper.py"],
     "parameters": {
+      "hostname": {
+        "description": "Hostname of metric, as configured with Hostname in collectd",
+        "type": "Optional[String[1]]"
+      },
       "metric": {
         "description": "Name of metric, e.g. load/load-relative",
         "type": "String[1]"

tasks/getval.py

@@ -8,11 +8,24 @@
 from task_helper import TaskHelper
 
 
-HOSTNAME = socket.gethostname()
 class GetVal(TaskHelper):
+    def get_metric(self, hostname, metric):
+        fullmetric = hostname+'/'+metric
+        return subprocess.check_output(['/usr/bin/collectdctl', 'getval',fullmetric]).rstrip().decode().split('\n')
+
     def task(self, args):
-        fullmetric = HOSTNAME+'/'+args['metric']
-        results = subprocess.check_output(['/usr/bin/collectdctl', 'getval',fullmetric]).rstrip().decode().split('\n')
+        if 'hostname' in args:
+            hosts = [args['hostname']]
+        else:
+            hosts = [socket.gethostname(), socket.getfqdn()]
+
+        for host in hosts:
+            try:
+                results = self.get_metric(host, args['metric'])
+                break
+            except:
+                continue
+
         values = { k:v for k,v in (x.split('=')  for x in results)}
         return {
                   'metric': args['metric'],