add bench-bot infra docs

README.md

@@ -9,6 +9,8 @@ many repositories) for our CI pipelines.
   - [Usage](#check_dependent_project-usage)
   - [Explanation](#check_dependent_project-explanation)
   - [Implementation](#check_dependent_project-implementation)
+- [bench-bot](#bench_bot)
+  - [Infrastructure](#bench_bot_infra)
 
 # check_dependent_project <a name="check_dependent_project"></a>
 
@@ -144,3 +146,73 @@ typechecking would fail.
 
 The check is currently limited to `cargo check` but optimally it should
 [entail the whole CI pipeline of `$dependent_repo`](https://github.com/paritytech/ci_cd/issues/234).
+
+# bench-bot <a name="bench_bot"></a>
+  - Bot that runs benchmark commands for users .
+  - Uses gitlab-runner to run the jobs.
+  - Users posts a comment on a PR in substrate repo  with the command that needs to run and the bot runs it.
+
+  E. G. `/cmd queue -c bench-bot $ pallet dev pallet_balances`
+
+## Infrastrcture <a name="#bench_bot_infra"></a>
+
+This bot runs on [bm3 machine](https://gitlab.parity.io/parity/devops/-/blob/master/inventory.yaml#L485),
+currently maintained by CI/CD team.
+
+### Configuration requirements:
+The machine needs to configred as a production gitlab-runer.
+
+Config requirements:
+  * gitlab_runner_executor: shell
+  * gitlab_runner_additional_tags: bench-bot
+  * os: ubuntu20
+  * provider: ovh
+  * HOME for `gitlab-runner` needs to  be in `/home` because this is monunted on a disk witk more space then the root partition
+and there will be a lot of rust code compiled
+  * install rustup for gitlab-runner user
+  * set default rustup
+  * install toolchain nightly
+  * add wasm target
+  * install cmake
+
+All those requirements are saved in an ansible role called `rustup`
+TODO: add link to rustup role once the PR is merged
+
+### Ansible
+Because there is only one host running code for this bot, one needs to create
+a test VM and add it to inventory everywhere `bm3` is mentiond.
+
+```
+        test-bench-bot:
+          ansible_host: 34.141.84.244
+          os: ubuntu20
+          provider: ovh
+          gitlab_runner_executor: shell
+          gitlab_runner_additional_tags: bench-bot
+          ### required for rustup ransible role
+          # Install rustup, and rust toolchain as defined value.
+          rustup_user: gitlab-runner
+          # Adds {HOME/.cargo/bin} to user's PATH
+          rustup_configure_shell: true
+          # do not install any cargo crates
+          rustup_cargo_crates: []
+```
+
+**When creating the VM helps a lot if you include your ssh public key**
+```
+/home/radu/.ssh/id_rsa_yubikey.pub
+```
+
+Test the ansible role from `parity/devops`
+```
+ansible-playbook ansible/gitlab-runner.yaml  -l test-bench-bot -u radupopa2010  -t gitlab-runner-benchmarks-weights-provision
+```
+
+### Test
+
+In order not to disrupt the service, JP created a test command that uses gitlab tag `test-bench-bot`
+
+1. Fisrt create a dummy PR in substrate repo like [this one](https://github.com/paritytech/substrate/pull/11566)
+2. Add a comment `/cmd queue -c test-bench-bot $ pallet dev pallet_balances`
+3. Wait a bit and check for a commnet from the bot with the job that started
+