Added optional region parameter. Fail if you specify an ELB that doesn't exist.

Boto blindly assumes the us-east-1 region if you don't hardcode a
region in it's config, so you could end up attempting to modify ELB's
in one region from a totally different region.  If a region isn't
specified then default to the region that the module is being run
within rather than the default us-east-1 region since it's a pretty
safe assumption that you intend to work on the ELB's within your
current region.

Also throw an error if a specified ELB instance doesn't exist.  The old
behavior would be to silently succeed with changed=false, so if you had
so much as a typo in the name of your ELB (or were in the wrong region
like my initial testing) you wouldn't get a clear indication that a
problem had occurred.

library/cloud/ec2_elb

@@ -25,7 +25,7 @@ description:
     if state=absent is passed as an argument.
   - Will be marked changed when called only if there are ELBs found to operate on.
 version_added: "1.2"
-requirements: [ "boto" ]
+requirements: [ "boto", "urllib2" ]
 author: John Jarvis
 options:
   state:
@@ -53,6 +53,11 @@ options:
       - AWS Access API key
     required: false
     default: None
+  ec2_region:
+    description:
+      - AWS region of your load balancer.  If not set then the region in which
+        this module is running will be used.
+    required: false
 
 """
 
@@ -81,23 +86,41 @@ import time
 import sys
 import os
 
+AWS_REGIONS = ['ap-northeast-1',
+               'ap-southeast-1',
+               'ap-southeast-2',
+               'eu-west-1',
+               'sa-east-1',
+               'us-east-1',
+               'us-west-1',
+               'us-west-2']
+
 try:
     import boto
+    import boto.ec2.elb
+    from boto.regioninfo import RegionInfo
 except ImportError:
     print "failed=True msg='boto required for this module'"
     sys.exit(1)
 
+try:
+    import urllib2
+except ImportError:
+    print "failed=True msg='urllib2 required for this module'"
+    sys.exit(1)
 
 class ElbManager:
     """Handles EC2 instance ELB registration and de-registration"""
 
     def __init__(self, module, instance_id=None, ec2_elbs=None,
-                 ec2_access_key=None, ec2_secret_key=None):
+                 ec2_access_key=None, ec2_secret_key=None, ec2_region=None):
         self.ec2_access_key = ec2_access_key
         self.ec2_secret_key = ec2_secret_key
         self.module = module
         self.instance_id = instance_id
+        self.ec2_region = ec2_region
         self.lbs = self._get_instance_lbs(ec2_elbs)
+
         # if there are no ELBs to operate on
         # there will be no changes made
         if len(self.lbs) > 0:
@@ -121,6 +144,17 @@ class ElbManager:
             lb.register_instances([self.instance_id])
             self._await_elb_instance_state(lb, 'InService')
 
+    def exists(self, lbtest):
+        """ Verify that the named ELB actually exists """
+        
+        found = False
+        for lb in self.lbs:
+            if lb.name == lbtest:
+                found=True
+                break
+        return found
+
+
     def _await_elb_instance_state(self, lb, awaited_state):
         """Wait for an ELB to change state
         lb: load balancer
@@ -140,9 +174,12 @@ class ElbManager:
                   are attached to self.instance_id"""
 
         try:
-            elb = boto.connect_elb(self.ec2_access_key, self.ec2_secret_key)
+            endpoint="elasticloadbalancing.%s.amazonaws.com" % self.ec2_region
+            connect_region = RegionInfo(name=self.ec2_region, endpoint=endpoint)
+            elb = boto.ec2.elb.ELBConnection(self.ec2_access_key, self.ec2_secret_key, region=connect_region)
         except boto.exception.NoAuthHandlerFound, e:
             self.module.fail_json(msg=str(e))
+
         elbs = elb.get_all_load_balancers()
 
         if ec2_elbs:
@@ -165,13 +202,15 @@ def main():
             instance_id={'required': True},
             ec2_elbs={'default': None, 'required': False},
             ec2_secret_key={'default': None, 'aliases': ['EC2_SECRET_KEY']},
-            ec2_access_key={'default': None, 'aliases': ['EC2_ACCESS_KEY']}
+            ec2_access_key={'default': None, 'aliases': ['EC2_ACCESS_KEY']},
+            ec2_region={'default': None, 'required': False, 'choices':AWS_REGIONS}
         )
     )
 
     ec2_secret_key = module.params['ec2_secret_key']
     ec2_access_key = module.params['ec2_access_key']
     ec2_elbs = module.params['ec2_elbs']
+    ec2_region = module.params['ec2_region']
 
     if module.params['state'] == 'present' and 'ec2_elbs' not in module.params:
         module.fail_json(msg="ELBs are required for registration")
@@ -181,9 +220,28 @@ def main():
     if not ec2_access_key and 'EC2_ACCESS_KEY' in os.environ:
         ec2_access_key = os.environ['EC2_ACCESS_KEY']
 
+    if not ec2_region and 'EC2_REGION' in os.environ:
+        ec2_region = os.environ['EC2_REGION']
+
+    if not ec2_region:
+        response = urllib2.urlopen('http://169.254.169.254/latest/meta-data/placement/availability-zone')
+        az = response.read()
+        for r in AWS_REGIONS:
+            if az.startswith(r):
+                ec2_region = r
+                break
+
+        if not ec2_region:
+            module.fail_json(msg = str("ec2_region not specified and unable to determine region from AWS."))
+
     instance_id = module.params['instance_id']
     elb_man = ElbManager(module, instance_id, ec2_elbs, ec2_access_key,
-                         ec2_secret_key)
+                         ec2_secret_key, ec2_region=ec2_region)
+
+    for elb in [ ec2_elbs ]:
+        if not elb_man.exists(elb):
+            str="ELB %s does not exist" % elb
+            module.fail_json(msg=str)
 
     if module.params['state'] == 'present':
         elb_man.register()