feat: assign a unique random name to each run context

If the run context has a parent, both share the same unique random
name. A composite action does not have a run context of its own, it
re-uses the run context of the job that calls it: this is when a
parent is used and needed.

There may be any level of parent / child relationship and ensureRandom
name recursively look for the first parent with a non empty random.

act/runner/run_context.go

@@ -52,6 +52,7 @@ type RunContext struct {
 	Masks               []string
 	cleanUpJobContainer common.Executor
 	caller              *caller // job calling this RunContext (reusable workflows)
+	randomName          string
 	networkName         string
 	networkCreated      bool
 }
@@ -391,6 +392,25 @@ func (rc *RunContext) startHostEnvironment() common.Executor {
 	}
 }
 
+func (rc *RunContext) ensureRandomName(ctx context.Context) {
+	if rc.randomName == "" {
+		logger := common.Logger(ctx)
+		if rc.Parent != nil {
+			// composite actions inherit their run context from the parent job
+			rootRunContext := rc
+			for rootRunContext.Parent != nil {
+				rootRunContext = rootRunContext.Parent
+			}
+			rootRunContext.ensureRandomName(ctx)
+			rc.randomName = rootRunContext.randomName
+			logger.Debugf("RunContext inherited random name %s from its parent", rc.Name, rc.randomName)
+		} else {
+			rc.randomName = common.MustRandName(16)
+			logger.Debugf("RunContext %s is assigned random name %s", rc.Name, rc.randomName)
+		}
+	}
+}
+
 func (rc *RunContext) getNetworkCreated(ctx context.Context) bool {
 	rc.ensureNetworkName(ctx)
 	return rc.networkCreated

act/runner/run_context_test.go

@@ -937,3 +937,18 @@ func Test_waitForServiceContainer(t *testing.T) {
 		m.AssertExpectations(t)
 	})
 }
+
+func TestRunContext_ensureRandomName(t *testing.T) {
+	parent := &RunContext{
+		Name: "parentname",
+	}
+	rc := &RunContext{
+		Name:   "runname",
+		Parent: parent,
+	}
+
+	parent.ensureRandomName(t.Context())
+	assert.NotEmpty(t, parent.randomName)
+	rc.ensureRandomName(t.Context())
+	assert.Equal(t, parent.randomName, rc.randomName)
+}