# Optimizing 'gather\_facts' response time over networking devices **URL:** \ **Category:** Ansible Project\ **Created:** [April 9, 2021, 5:31pm UTC](https://forum.ansible.com/t/optimizing-gather-facts-response-time-over-networking-devices/34955 "2021-04-09T17:31:32Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![actionmystique](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/actionmystique/32/1678_2.png) [@actionmystique](https://forum.ansible.com/u/actionmystique)\ **Post date:** [April 9, 2021, 5:31pm UTC](https://forum.ansible.com/t/optimizing-gather-facts-response-time-over-networking-devices/34955/1 "2021-04-09T17:31:32Z")
With: - ansible 3.2.0 (pip3) - ansible-base 2.10.7 (pip3) The goal is twofold:- gather the facts **only from the local cache** when the cache is not empty and its timeout \ has not expired - contact the remote network device **only when** the cache is empty or the timeout has expired I made some tests with the following settings in /etc/ansible/ansible.cfg: fact\_caching = redis fact\_caching\_timeout = 3600 fact\_caching\_connection = localhost:6379:0:\ Making sure that redis is running with **requirepass \** in /etc/redis/redis.conf: $ sudo systemctl status redis ● redis-server.service - Advanced key-value store Loaded: loaded (/lib/systemd/system/redis-server.service; enabled; vendor preset: enabled) Active: active (running) since Fri 2021-04-09 12:09:54 CEST; 7h ago Docs: [http://redis.io/documentation](http://redis.io/documentation), man:redis-server(1) Main PID: 1610 (redis-server) Status: “Ready to accept connections” Tasks: 5 (limit: 18973) Memory: 5.7M CGroup: /system.slice/redis-server.service └─1610 /usr/bin/redis-server 127.0.0.1:6379 Apr 09 12:09:54 host systemd[1]: Starting Advanced key-value store… Apr 09 12:09:54 host systemd[1]: Started Advanced key-value store. Running the following simple play over an IOS device: - “Gathering Facts” took several seconds indicating that the remote device has been contacted - “Pinging remote device to create/update facts cache” was almost instantaneous - name: Gathering remote device facts preferably from the cache hosts: all vars: ansible\_connection: network\_cli gather\_facts: yes strategy: debug tasks: - name: Pinging remote device to create/update facts cache ping: leads to: ansible-playbook 2.10.7 config file = /etc/ansible/ansible.cfg ansible python module location = /usr/local/lib/python3.9/dist-packages/ansible executable location = /usr/local/bin/ansible-playbook python version = 3.9.4 (default, Apr 4 2021, 19:38:44) [GCC 10.2.1 20210401] Using /etc/ansible/ansible.cfg as config file Parsed lab/hosts inventory source with ini plugin redirecting (type: cache) ansible.builtin.redis to community.general.redis Redis connection: Redis\\>\> redirecting (type: callback) ansible.builtin.yaml to community.general.yaml redirecting (type: callback) ansible.builtin.yaml to community.general.yaml Skipping callback ‘default’, as we already have a stdout callback. Skipping callback ‘minimal’, as we already have a stdout callback. Skipping callback ‘oneline’, as we already have a stdout callback. ---
**Author:** ![actionmystique](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/actionmystique/32/1678_2.png) [@actionmystique](https://forum.ansible.com/u/actionmystique)\ **Post date:** [April 10, 2021, 5:39am UTC](https://forum.ansible.com/t/optimizing-gather-facts-response-time-over-networking-devices/34955/2 "2021-04-10T05:39:08Z")
I retried the playbook and I rectify a previous assertion: with ‘ **gather\_facts: no** ’, the **facts are read from the cache** as expected. However, I confirm that with ‘ **gather\_facts: yes** ’, the **facts are always gathered from the remote host, regardless of the cache timeout value.** I also tried the same playbook over a compute node (Ubuntu server) (without ‘ansible\_connection: network\_cli’ of course) , and I got the same results: the facts are always gathered from the remote device at each run with ‘ **gather\_facts: yes** ’ It seems that I’m misunderstanding the real meaning of gather\_facts and the primary goal of the thread does not seem to be implemented by ansible and should be manually implemented somehow by the user. I suppose that it also means that when the cache timeout expires, all the ‘ansible\_facts’ data disappear from the cache and that’s it. If nothing is done by the user to gather them from the remote device, they are not accessible anymore. If the timeout expiration is supposed to trigger some background facts gathering from the remote device, it must happen during some playbook run, otherwise it is lost. - If I run the first playbook with ‘ **gather\_facts: yes** ’ **,** then run it before the cache timeout expires with ‘ **gather\_facts: no** ’, the ‘ansible\_facts’ continue to be accessible. - however, if I run the first playbook with ‘ **gather\_facts: yes** ’ **,** wait for the cache timeout to expire and then run it with ‘ **gather\_facts: no** ’, the ‘ansible\_facts’ are not accessible anymore. Nothing is triggered. Is the last behavior expected? ---
**Author:** ![system](https://us1.discourse-cdn.com/ansible/original/1X/1882d9a01da5d8996a862359b0913cc568a39b84.svg) [@system](https://forum.ansible.com/u/system)\ **Post date:** [April 12, 2021, 4:36pm UTC](https://forum.ansible.com/t/optimizing-gather-facts-response-time-over-networking-devices/34955/3 "2021-04-12T16:36:35Z")
[https://docs.ansible.com/ansible/latest/reference\_appendices/config.html#default-gathering](https://docs.ansible.com/ansible/latest/reference_appendices/config.html#default-gathering) ^ set to smart and you can ignore `gather_facts` except for those plays in which you want to force it. ---
**Author:** ![actionmystique](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/actionmystique/32/1678_2.png) [@actionmystique](https://forum.ansible.com/u/actionmystique)\ **Post date:** [April 13, 2021, 12:57pm UTC](https://forum.ansible.com/t/optimizing-gather-facts-response-time-over-networking-devices/34955/4 "2021-04-13T12:57:12Z")
@Brian Coca I have already tried to set **gathering=smart** in ansible.cfg or **export ANSIBLE\_GATHERING=smart** Nothing happens during the second play run when the **fact\_caching\_timeout** expires after the first one. Anyway, even if it worked, there would be a major drawback: its **unpredictability**. For instance, let’s assume: - **fact\_caching\_timeout** expires after the first play run - one of the **ansible\_facts** is used at the beginning of the second run to perform a **group\_by** with **ansible\_net\_version** for instance Even if the smart feature works and kicks in after the second run begins, there is a high probability that the playbook will fail due to **ansible\_net\_version** being undefined, depending on when exactly it does kick in and how long it takes to retrieve the data from the remote device. On top of that, there is no way to run a module to gather facts when that variable is undefined, because there is no **setup** equivalence in the networking ecosystem. IIUC, when **gather\_facts: yes** is used, it launches the correct platform-dependent gathering facts module based on the value of predefined **ansible\_network\_os**. And there is not a single umbrella module to take care of that logic. Hence my initial wrong belief that **gather\_facts: yes** would first check if the **fact\_caching\_timeout** is about to expire (for instance halfway through the timeout) before deciding whether to gather facts from the remote device or not. With that type of logic, we could count on the fact that after that call, the **ansible\_facts** would be accessible for sure\*\*.\*\* **As a summary:** - the smart feature does not work over networking devices - even if it did, it would be: - **gathering = explicit** - run a background playbook every halfway through the **fact\_caching\_timeout** for all remote devices ---
**Author:** ![actionmystique](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/actionmystique/32/1678_2.png) [@actionmystique](https://forum.ansible.com/u/actionmystique)\ **Post date:** [April 13, 2021, 12:59pm UTC](https://forum.ansible.com/t/optimizing-gather-facts-response-time-over-networking-devices/34955/5 "2021-04-13T12:59:20Z")
… with **gather\_facts: yes**. (end of last sentence) ---
**Author:** ![system](https://us1.discourse-cdn.com/ansible/original/1X/1882d9a01da5d8996a862359b0913cc568a39b84.svg) [@system](https://forum.ansible.com/u/system)\ **Post date:** [April 13, 2021, 4:43pm UTC](https://forum.ansible.com/t/optimizing-gather-facts-response-time-over-networking-devices/34955/6 "2021-04-13T16:43:36Z")
the time out only affects facts when first fetched, once in memory they should not expire or you would lose facts mid run and become inconsistent. if you want to force retry you can check datetime facts yourself and make fact gathering conditional on that on the 2nd play.