Fix: reduce “Waiting on concurrency group” (#8)

When setting the attribute concurrency_group on deploy steps, set concurrency_method: eager. By default (ordered), a BuildKite build’s deploy steps will wait for all the smoke_test and build steps of a previous build. This is a problem in rollbacks, which run much faster than normal builds because they have no smoke_test or build steps, so they are likely to reach their deploy steps before the previous build does.

pipeline.go

@@ -230,6 +230,9 @@ func lowerStep(step Step, context *Context, stepContext *StepContext) (Step, err
 		step["concurrency"] == nil && step["concurrency_group"] == nil {
 		step["concurrency_group"] = fmt.Sprintf("%s/%s", stepContext.EnvironmentName, context.BuildkitePipelineSlug)
 		step["concurrency"] = 1
+		if step["concurrency_method"] == nil {
+			step["concurrency_method"] = "eager"
+		}
 	}
 
 	return step, nil

testdata/basic_master.out.yaml

@@ -30,6 +30,7 @@ steps:
   command: deploy
   concurrency: 1
   concurrency_group: dev/myrepo
+  concurrency_method: eager
   env:
     ENVIRONMENT: dev
     JOBSWORTH_CAUTIOUS: "0"
@@ -60,6 +61,7 @@ steps:
   command: integrationtest
   concurrency: 1
   concurrency_group: dev/myrepo
+  concurrency_method: eager
   env:
     JOBSWORTH_CAUTIOUS: "0"
     JOBSWORTH_CODE_VERSION: ""
@@ -74,6 +76,7 @@ steps:
   command: deploy
   concurrency: 1
   concurrency_group: prod/myrepo
+  concurrency_method: eager
   env:
     ENVIRONMENT: prod
     JOBSWORTH_CAUTIOUS: "1"
@@ -104,6 +107,7 @@ steps:
   command: integrationtest
   concurrency: 1
   concurrency_group: prod/myrepo
+  concurrency_method: eager
   env:
     JOBSWORTH_CAUTIOUS: "0"
     JOBSWORTH_CODE_VERSION: ""