FPO-423: Adds manual for rolling back a training model

source/manual/how-to-rollback-training-models.html.md

@@ -0,0 +1,60 @@
+---
+owner_slack: "#trade-tariff-infrastructure"
+title: Rolling back training models
+section: Deployment
+layout: manual_layout
+parent: "/manual.html"
+---
+
+This document describes how to rollback training models that have been deployed with Serverless to
+our AWS environments.
+
+## Rollback process
+
+1. Identify the model you want to rollback to. This could be the previous model or a specific version of the model.
+2. Adjust the [search-config.toml][search-config] file to point to the model you want to rollback to.
+3. Open a PR with the changes to the `search-config.toml` file.
+4. Once the PR is merged, the changes will be deployed to the `fpo-search` environment.
+
+### Identifying the model to rollback to
+
+Models have iterations on versions and the latest iteration is the one that will be actively deployed today.
+
+Inactive model versions (e.g. previous iterations/those not in an active development branch) are stored in the model s3 bucket.
+
+#### Easiest solution
+
+Assuming you know the code that introduced the failure you can checkout the code history of the [search-config.toml][search-config] file and see what model version was being used at that time.
+
+The model version prior is typically going to be the version you want.
+
+#### List recent iterations of models
+
+In the [FPO search lambda][fpo-search-lambda-repo] repository, run the following command to list the most recent iterations of the last n models:
+
+> Note: You will need to have the AWS CLI installed and configured with the correct permissions.
+
+```bash
+.circleci/bin/getversions <n>
+```
+
+This will output like so:
+
+```bash
+1.5.1-6b3c782
+1.6.0-262a174
+1.7.0-4595f36
+```
+
+You can work out what the currently deployed model version is by making a GET request to the healthcheck endpoint:
+
+```bash
+curl --silent -X GET https://search.dev.trade-tariff.service.gov.uk/healthcheck -H 'Content-Type: application/json' | jq -r '.model_version'
+
+1.7.0-4595f36
+```
+
+You can then review the release notes and benchmarks for these models to know which one you want to rollback to.
+
+[search-config]: https://github.com/trade-tariff/trade-tariff-lambdas-fpo-search/blob/main/search-config.toml
+[fpo-search-lambda-repo]: https://github.com/trade-tariff/trade-tariff-lambdas-fpo-search