# Developing a vars\_plugin **URL:** \ **Category:** Ansible Project\ **Created:** [September 11, 2014, 3:27pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182 "2014-09-11T15:27:00Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Guy\_Matz1](https://avatars.discourse-cdn.com/v4/letter/g/b5e925/32.png) [@Guy\_Matz1](https://forum.ansible.com/u/Guy_Matz1)\ **Post date:** [September 11, 2014, 3:27pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/1 "2014-09-11T15:27:00Z")
Hi! Anyone have any advice on developing a vars\_plugin? This may sound kinda screwy, but for a chef → ansible transition I need to access data from a chef data\_bag in an ansible play . . . I’m able to get the chef data using pychef, but I’m having issues when trying to run the code within vars\_plugin code: import chef def get\_dbag\_data(): chef\_api = chef.autoconfigure() dbag, dbag\_item = ‘dbag’, ‘dbag\_item’ bag = chef.DataBag(dbag) # some debugging shows the problem is here on the second run. . ! item = bag[dbag\_item] return item.to\_dict() The code above works outside of ansible, but when run in ansible it seems to get run twice, and fails on the “bag = chef.DataBag(dbag)” line the second time around. Any thoughts would be greatly appreciated! Thanks! Guy ---
**Author:** ![sivel](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/sivel/32/1198_2.png) [@sivel](https://forum.ansible.com/u/sivel)\ **Post date:** [September 11, 2014, 3:40pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/2 "2014-09-11T15:40:27Z")
Perhaps you could show your vars\_plugin? There is the potential that it could be run twice, depending on where you call that code from. The 3 following methods are all run 1 time in ansible.inventory.Inventory: plugin.get\_group\_vars plugin.run plugin.get\_host\_vars Also, as a heads up, this is probably a better discussion for ansible-devel. ---
**Author:** ![Guy\_Matz1](https://avatars.discourse-cdn.com/v4/letter/g/b5e925/32.png) [@Guy\_Matz1](https://forum.ansible.com/u/Guy_Matz1)\ **Post date:** [September 11, 2014, 4:11pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/3 "2014-09-11T16:11:57Z")
Matt, Thanks for the reply! Here’s the full code import chef def get\_dbag\_data(): chef\_api = chef.autoconfigure() dbag, dbag\_item = ‘twelve\_factor\_environment’, ‘scratch-gmatz-sandbox-app-web’ bag = chef.DataBag(dbag) item = bag[dbag\_item] return item.to\_dict() class VarsModule(object): def **init** (self, inventory): self.inventory = inventory self.group\_cache = {} def run(self, host, vault\_password=None): inventory = self.inventory results = get\_dbag\_data() return results Thanks! ---
**Author:** ![Guy\_Matz](https://avatars.discourse-cdn.com/v4/letter/g/57b2e6/32.png) [@Guy\_Matz](https://forum.ansible.com/u/Guy_Matz)\ **Post date:** [September 11, 2014, 4:12pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/4 "2014-09-11T16:12:30Z")
migrated to ansible-devel . . . thanks! ---
**Author:** ![Serge\_van\_Ginderacht](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@Serge\_van\_Ginderacht](https://forum.ansible.com/u/Serge_van_Ginderacht)\ **Post date:** [September 11, 2014, 5:40pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/5 "2014-09-11T17:40:04Z")
​Please note that run() was kept around for backwards compatibility. Before 1.7, this was the only exposed function in vars\_plugins​, and it was supposed to return \*all\* calculated vars for a particular host. See lib/ansible/inventory/vars\_plugins/noop.py for the signatures. For newly written plugins, just use get\_group/host\_vars. Those are called just once for every group/host. ---
**Author:** ![Serge\_van\_Ginderacht](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@Serge\_van\_Ginderacht](https://forum.ansible.com/u/Serge_van_Ginderacht)\ **Post date:** [September 11, 2014, 5:51pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/6 "2014-09-11T17:51:16Z")
​Hi Guy, ​ > import chef > > def get\_dbag\_data(): >     chef\_api = chef.autoconfigure() >     dbag, dbag\_item = 'twelve\_factor\_environment', > 'scratch-gmatz-sandbox-app-web' >     bag = chef.DataBag(dbag) >     item = bag[dbag\_item] >     return item.to\_dict() > > class VarsModule(object): >     def \_\_init\_\_(self, inventory): >         self.inventory = inventory >         self.group\_cache = {} >     def run(self, host, vault\_password=None): >         inventory = self.inventory >         results = get\_dbag\_data() >         return results ​So, you are using the run() function here, which gets a host as a parameter​ for which you are supposed tro return the its vars. I have no clue what the chef code does, but this sounds like it always returns data for that sandbox web host? How does ""bag = chef.DataBag(dbag)"" fail at the second run? (It runs - at least twice - so you have - at least - two hosts in your inventory). The code in the VarsModule constructor is not used, also the inventory var in run() - you might leave those out. You'll need to give me some more info on that chef code, what it does, and what exactly you try to retrieve, and how you expect to put this in ansible.   Serge ---
**Author:** ![Guy\_Matz1](https://avatars.discourse-cdn.com/v4/letter/g/b5e925/32.png) [@Guy\_Matz1](https://forum.ansible.com/u/Guy_Matz1)\ **Post date:** [September 11, 2014, 7:59pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/7 "2014-09-11T19:59:18Z")
Serge, Thanks for the reply! The chef code retrieves some information form the chef server that I want to make available as vars (either host vars or group vars, or whatever) to the ansible run. Yeah, I see what you mean about some of the vars in my code . . . what you’re seeing is a hacked up attempt to get something working . . . here it is again, a bit cleaner (prints are included to show flow) ~/Code/mdansible⟫ cat inventory/vars\_plugins/chefdb.py import chef #print(“In chefdb.py”) class VarsModule(object): def **init** (self, inventory): “”" constructor “”" # Apparently nothing needed here ##print(“In **init** with %s” % dir(inventory) ) pass def run(self, host, vault\_password=None): #print("Starting run . .. ") api = chef.autoconfigure() #print(“In **init** , api = %s” % api ) dbag, dbag\_item = ‘twelve\_factor\_environment’, ‘scratch-gmatz-sandbox-app-web’ #print(“dbag = %s” % dbag) bag = chef.DataBag(dbag) #print bag item = bag[dbag\_item] return item.to\_dict() if **name** == ‘ **main** ’: v = VarsModule(‘inv’) print v.run(‘hostname’) Here it is failing when run by ansible: ⟫ ansible-playbook -i inventory site.yml Traceback (most recent call last): File “/opt/ansible/bin/ansible-playbook”, line 324, in sys.exit(main(sys.argv[1:])) File “/opt/ansible/bin/ansible-playbook”, line 160, in main inventory = ansible.inventory.Inventory(options.inventory, vault\_password=vault\_pass) File “/opt/ansible/lib/ansible/inventory/ **init**.py”, line 149, in **init** host.vars = utils.combine\_vars(host.vars, self.get\_host\_variables([host.name](http://host.name), vault\_password=self.\_vault\_password)) File “/opt/ansible/lib/ansible/inventory/ **init**.py”, line 445, in get\_host\_variables self.\_vars\_per\_host[hostname] = self.\_get\_host\_variables(hostname, vault\_password=vault\_password) File “/opt/ansible/lib/ansible/inventory/ **init**.py”, line 457, in \_get\_host\_variables vars\_results = [plugin.run(host, vault\_password=vault\_password) for plugin in self.\_vars\_plugins if hasattr(plugin, ‘run’)] File “/home/gmatz/Code/mdansible/inventory/vars\_plugins/chefdb.py”, line 20, in run bag = chef.DataBag(dbag) File “/usr/local/lib/python2.7/dist-packages/chef/base.py”, line 58, in **init** data = self.api[self.url] TypeError: ‘NoneType’ object has no attribute ‘ **getitem** ’ ---
**Author:** ![Guy\_Matz1](https://avatars.discourse-cdn.com/v4/letter/g/b5e925/32.png) [@Guy\_Matz1](https://forum.ansible.com/u/Guy_Matz1)\ **Post date:** [September 11, 2014, 9:37pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/8 "2014-09-11T21:37:55Z")
Apologies!! Turns out to be a problem when I make my call to the chef DB and it has nothing to return . . . If I wrap the code that could fail in a try block it works: def get\_host\_vars(self, host, vault\_password=None): print(“Getting vars for host %s” % host.name) data = {} try: api = chef.autoconfigure() dbag, dbag\_item = ‘twelve\_factor\_environment’, ‘scratch-gmatz-sandbox-app-web’ bag = chef.DataBag(dbag) except Exception as e: return data #raise errors.AnsibleError(‘Unable to get chef data: %s’ % e.message) for k, v in bag[dbag\_item].raw\_data.items(): data[k] = v return data Two more question, though! ☹ 1. Do I need to return the data in a certain format? I don’t seem to be able to access it . . . is there a good way to test this? I’m just dumping everything I can think of in a template 2. Does anyone know if I can restrict this var lookup to the hosts in my play? The chef query takes a few seconds Thanks again, Guy ---
**Author:** ![Serge\_van\_Ginderacht](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@Serge\_van\_Ginderacht](https://forum.ansible.com/u/Serge_van_Ginderacht)\ **Post date:** [September 12, 2014, 7:15am UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/9 "2014-09-12T07:15:36Z")
> 1. Do I need to return the data in a certain format? I don't seem to be > able to access it . . . is there a good way to test this? I'm just > dumping everything I can think of in a template ​Should be a dict holding all variables for the host/group called for. ​ > 2. Does anyone know if I can restrict this var lookup to the hosts in my > play? The chef query takes a few seconds ​That is how it worked before 1.7, but the downside there was ​you had repeated calls for every host, re-parsing the same groups over and over. Depending how the Chef code works, you could maybe do 1 call in the constructor to retrieve all data in 1 call, then return it per host and or group in the other functions. Or try to limit calls to get data for big groups only; or implement some caching. I also have this utility that you can use to dump your data in a json, which you can then retrieve via an ansible inventory script: [https://github.com/ginsys/ansible-plugins/blob/devel/bin/ansible-inventory](https://github.com/ginsys/ansible-plugins/blob/devel/bin/ansible-inventory)   Serge ---
**Author:** ![Guy\_Matz1](https://avatars.discourse-cdn.com/v4/letter/g/b5e925/32.png) [@Guy\_Matz1](https://forum.ansible.com/u/Guy_Matz1)\ **Post date:** [September 12, 2014, 7:15pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/10 "2014-09-12T19:15:19Z")
Serge, Thank you for your effort here! So, do you have any idea how I can get at that data in a template? Regards, Guy ---
**Author:** ![Michael\_DeHaan1](https://avatars.discourse-cdn.com/v4/letter/m/5e9695/32.png) [@Michael\_DeHaan1](https://forum.ansible.com/u/Michael_DeHaan1)\ **Post date:** [September 12, 2014, 7:45pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/11 "2014-09-12T19:45:27Z")
A fact module to query your databag could be one thing, though it seems like you should just shoot it in the head and switch over to vault. Your inventory script could also choose to provide this data perhaps, if it’s something dynamic. ---
**Author:** ![Serge\_van\_Ginderacht](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@Serge\_van\_Ginderacht](https://forum.ansible.com/u/Serge_van_Ginderacht)\ **Post date:** [September 12, 2014, 9:25pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/12 "2014-09-12T21:25:22Z")
​ That's what he's trying to do, and what we are troubleshooting 🙂 ---
**Author:** ![Serge\_van\_Ginderacht](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@Serge\_van\_Ginderacht](https://forum.ansible.com/u/Serge_van_Ginderacht)\ **Post date:** [September 12, 2014, 9:30pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/13 "2014-09-12T21:30:03Z")
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**Author:** ![Michael\_DeHaan1](https://avatars.discourse-cdn.com/v4/letter/m/5e9695/32.png) [@Michael\_DeHaan1](https://forum.ansible.com/u/Michael_DeHaan1)\ **Post date:** [September 12, 2014, 9:53pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/14 "2014-09-12T21:53:35Z")
“That’s what he’s trying to do, and what we are troubleshooting :)” I was replying to the discussion of lookup plugins, which I would suggest against. I don’t feel vars\_plugins are ideal either. ---
**Author:** ![Gabriel\_Burkholder](https://avatars.discourse-cdn.com/v4/letter/g/958977/32.png) [@Gabriel\_Burkholder](https://forum.ansible.com/u/Gabriel_Burkholder)\ **Post date:** [March 14, 2016, 10:25pm UTC](https://forum.ansible.com/t/developing-a-vars-plugin/16182/15 "2016-03-14T22:25:51Z")
Sorry to resurrect a zombie thread. I recently wrote a simple lookup plugin to pull down chef databags, using pychef’s search functionality. I found this to be (at least in my case) simpler and more performant than accessing databags directly in pychef. In theory, it should also allow you to query a chef server for more than just databags, however, this doesn’t seem to work in my testing. Thoughts? Comments? Criticisms? ` from ansible.errors import AnsibleError from ansible.plugins.lookup import LookupBase try: import chef except ImportError: AnsibleError(“Please pip install pychef to use this module”) class LookupModule(LookupBase): def run (self, terms, variables, \*\*kwargs): api = chef.autoconfigure() ret = for term in terms: chef\_results = for result in chef.Search(term, \*\*kwargs): chef\_results.append(result[‘raw\_data’]) ret.append(chef\_results) return ret ` Thank you! Gabriel Burkholder