Ansible nested loop using index.

[Lionel H]

Hi all, 

Hope I will find the information here :-)

I need to loop over 2 lists, the first one is just a list of Integers, things get tricky here because the second list needs the input from the first list to loop over. In fact, the list is included in a dictionary where keys are integers.

One example will be more self-explanatory:

1st list:

chains = [1, 2, 3, 4, 5]

2nd list:

chains_config:

    1:

        foo: bar

        configs:

            - type: routed

              version: 0.1

            - type: bridged

              version: 0.2

    2:

        foo: baz

        configs:

            - type: routed

              version: 1.0

            - type: bridged

              version: 1.1

... and 3, 4, 5 you get the idea.

So I need to loop over this configs key and the chains list is defined by the user input.

In python I would do this way:

for chain in chains:

     for config in chains_config[chain]['configs']:

         print(config.type).

Now, and to convert this into ansible code?

I hope that you get the point :-)

Best regards,

Lionel.

[Matt Martz]

What is your end goal?  How do you plan to use this data, assuming you could loop the way you want?

Something like the following:

"{{ chains|map('extract', chains_config)|map(attribute='configs')|flatten|map(attribute='type')|flatten }}"

Gives:

ok: [localhost] => {

    "msg": [

        "routed",

        "bridged",

        "routed",

        "bridged"

    ]

}

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@sivel
sivel.net

[Lionel H]

Hi matt, 

Thanks for your reply !

That's already a good example, But I need somehow also to retrieve the index which is the chain number.

Let's simplify and say we only have one type of deployment (routed or bridged):

chains_config:

    1:

        foo: bar

        configs:

            - type: bridged

              version: 0.2

    2:

        foo: baz

        configs:

            - type: routed

              version: 1.0

To briefly explain the context we have two type of network deployment (routed or bridged). Each of these network deployment have their own

set of network interfaces / VLANs. The VLAN used is guess from the chain number and type of deployment. And the type of deployment is specified in the chains_config dict.

On top of this network architecture a docker container is applied for network type / VLANs.

A dumb naive approach would be:

- name: Creating docker network for the chain

  include_role:

    name: docker_chain_network

  vars:

    docker_network:

      name: macvlan{{item.key}}0{{ '6' if item.value.type == 'routed' else '5' }}

      driver: macvlan

      driver_options:

        parent: "{{ 'eno52' if routed else 'eno51' }}".{{item.key}}0{{ '6' if item.value.type == routed else '5' }}"

  with: ? map/select ?

item.key ==> Would be each index of chains[] list (iteratively). 

item.value.type ==> Would be type of deployment based the index above; like in python: chains_config[item.key]['configs']['type']

docker_chain_network is just a role applying docker_network module with the vars passed to the role.

This is rather complex stuff. Thanks for taking your time and for your answers.

Best regards,

Lionel.

[Lionel H]

Replying to my-self,

I managed somehow to make some progress, but now the issue is that it merge the results like the following:

Given the following config:

chains_config:

    1:

        foo: bar

        configs:

            - type: bridged

              version: 0.2

    2:

        foo: baz

        configs:

            - type: routed

              version: 1.0

chains = [1, 2]

And using that loop with debug: 

- debug: msg="chain={{ item.0 }}, configs={{ item.1.type }}"

  with_nested:

    - "{{ chains }}"

    - "{{ chains |map('extract', chains_config) |map(attribute='configs') |list }}"

I have the following output:

ok: [server] => (item=None) => {

    "msg": "chain=1, configs=bridged"

}

ok: [server] => (item=None) => {

    "msg": "chain=1, configs=routed"

}

ok: [server] => (item=None) => {

    "msg": "chain=2, configs=bridged"

}

ok: [server] => (item=None) => {

    "msg": "chain=2, configs=routed"

}

Which is not really right as not bridged config is defined for chain 2 and no routed is defined for chain 1.

Best regards,

Lionel H.

[Kai Stian Olstad]

I haven't understood what your are trying in your previous mails, but based on this one you are looking for this?

- debug: msg="chain={{ item.key }}, configs={{ item.value.configs.0.type }}"
with_dict: "{{ chains_config }}"

If you would like to use the chains it would be something like this

- debug: msg="chain={{ item }}, configs={{ chains_config[item].configs.0.type }}"
with_item: "{{ chains }}"


--
Kai Stian Olstad

[Felix Fontein]

Hi Lionel,

I've written a lookup plugin
(https://github.com/felixfontein/ansible-dependentloop/) which you
could use for this:

- debug:
msg: "index={{ item.0 }} foo={{ chains_config[item.0].foo }}
type={{ index.1.type }} version={{ index.1.version }}"
with_dependent:
- chains
- "chains_config[item.0].configs"

Cheers,
Felix

[Lionel H]

Hi Felix,

Oh waw! Definitely what I was looking for. Shame that we have to resort to custom plugins to achieve such a common things..

In my findings I was hoping maybe to find some sort of lookup plugins to filter a dict based on a provided list of keys like:

{{ mydict | filter_by_keys([1, 2]) }} to only select those keys from the dictionary but it seems not yet implemented! Maybe a good entrypoint for me to start 

digging into ansible plugin creation :-)

Anyway, this is working now.

Huge thanks ;-)

Lionel.