IPS-1109: Canary deployments (#2520)

README.md

@@ -120,3 +120,18 @@ sam deploy --debug --config-file ./samconfig.toml --config-env dev-{{environment
 ```
 sam sync --watch --config-file samconfig.toml --config-env {{environment}} --stack-name core-back-dev-{{environment}} --region eu-west-2
 ```
+
+## Canaries
+When deploying using dev-deploy, the canary deployment strategy which will be used is set in LambdaDeploymentPreference and StepFunctionsDeploymentPreference in template.yaml file.
+
+When deploying using the pipeline, canary deployment strategy set in the pipeline will be used and override the default set in template.yaml.
+
+Canary deployments will cause a rollback if any canary alarms associated with a lambda or step-functions are triggered and a slack notification will be sent to #di-ipv-core-non-prod-alarms or #di-ipv-core-prod-alarms.
+
+To skip canaries such as when releasing urgent changes to production, set the last commit message to contain either of these phrases: [skip canary], [canary skip], or [no canary] as specified in the [Canary Escape Hatch guide](https://govukverify.atlassian.net/wiki/spaces/PLAT/pages/3836051600/Rollback+Recovery+Guidance#Escape-Hatch%3A-how-to-skip-canary-deployments-when-needed).
+`git commit -m "some message [skip canary]"`
+
+Note: To update LambdaDeploymentPreference or StepFunctionsDeploymentPreference, update the LambdaCanaryDeployment or StepFunctionsDeploymentPreference pipeline parameter in the [core-common-infra repository](https://github.com/govuk-one-login/ipv-core-common-infra/tree/main/terraform/deployments). To update the LambdaDeploymentPreference or StepFunctionsDeploymentPreference for a stack in dev using sam deploy, parameter override needs to be set in [samconfig.toml](./deploy/samconfig.toml):
+
+`--parameter-overrides LambdaDeploymentPreference=<define-strategy> \`
+`--parameter-overrides StepFunctionsDeploymentPreference=<define-strategy> \`

deploy/samconfig.toml

@@ -171,3 +171,12 @@ region = "eu-west-2"
 capabilities = "CAPABILITY_IAM"
 parameter_overrides = "Environment=\"dev-martins\" VpcStackName=\"network-shared-development\""
 parallel = "true"
+
+[dev-sre.deploy.parameters]
+stack_name = "core-back-dev-sre"
+s3_bucket = "aws-sam-cli-managed-default-samclisourcebucket-ec647gpjuo2w"
+s3_prefix = "sre-core-back-stack"
+region = "eu-west-2"
+capabilities = "CAPABILITY_IAM"
+parameter_overrides = "Environment=\"dev-sre\" LambdaDeploymentPreference=\"AllAtOnce\" StepFunctionsDeploymentPreference=\"ALL_AT_ONCE\" VpcStackName=\"network-shared-development\""
+parallel = "true"