feat(helm): add support for a `pre-ready` hook

Adds a new `pre-ready` hook type that runs after resources have been
created or updated, but before they're necessarily in a ready state.

This allows for charts that provision a resources using a subchart,
use a hook to configure those resources (for example, migrating a
database), and require that subchart resources be configured before
the pods in their chart are in a ready state. Using the `--wait`
flag with Helm will currently fail with these charts, making them
incompatible with the chart-testing tool.

Fixes #7740, fixes helm/chart-testing#202

Signed-off-by: Noah Lackstein <noah@lackstein.com>

pkg/action/install.go

@@ -344,6 +344,12 @@ func (i *Install) Run(chrt *chart.Chart, vals map[string]interface{}) (*release.
 		}
 	}
 
+	if !i.DisableHooks {
+		if err := i.cfg.execHook(rel, release.HookPreReady, i.Timeout); err != nil {
+			return i.failRelease(rel, fmt.Errorf("failed pre-ready: %s", err))
+		}
+	}
+
 	if i.Wait {
 		if err := i.cfg.KubeClient.Wait(resources, i.Timeout); err != nil {
 			return i.failRelease(rel, err)

pkg/release/hook.go

@@ -33,6 +33,7 @@ const (
 	HookPostUpgrade  HookEvent = "post-upgrade"
 	HookPreRollback  HookEvent = "pre-rollback"
 	HookPostRollback HookEvent = "post-rollback"
+	HookPreReady     HookEvent = "pre-ready"
 	HookTest         HookEvent = "test"
 )
 

pkg/releaseutil/manifest_sorter.go

@@ -61,6 +61,7 @@ var events = map[string]release.HookEvent{
 	release.HookPostUpgrade.String():  release.HookPostUpgrade,
 	release.HookPreRollback.String():  release.HookPreRollback,
 	release.HookPostRollback.String(): release.HookPostRollback,
+	release.HookPreReady.String():     release.HookPreReady,
 	release.HookTest.String():         release.HookTest,
 	// Support test-success for backward compatibility with Helm 2 tests
 	"test-success": release.HookTest,

pkg/releaseutil/manifest_sorter_test.go

@@ -62,7 +62,8 @@ metadata:
   annotations:
     "helm.sh/hook": post-install
 `,
-		}, {
+		},
+		{
 			name:  []string{"third"},
 			path:  "three",
 			kind:  []string{"ReplicaSet"},
@@ -74,7 +75,8 @@ metadata:
   annotations:
     "helm.sh/hook": no-such-hook
 `,
-		}, {
+		},
+		{
 			name:  []string{"fourth"},
 			path:  "four",
 			kind:  []string{"Pod"},
@@ -85,7 +87,8 @@ metadata:
   name: fourth
   annotations:
     nothing: here`,
-		}, {
+		},
+		{
 			name:  []string{"fifth"},
 			path:  "five",
 			kind:  []string{"ReplicaSet"},
@@ -97,14 +100,16 @@ metadata:
   annotations:
     "helm.sh/hook": post-delete, post-install
 `,
-		}, {
+		},
+		{
 			// Regression test: files with an underscore in the base name should be skipped.
 			name:     []string{"sixth"},
 			path:     "six/_six",
 			kind:     []string{"ReplicaSet"},
 			hooks:    map[string][]release.HookEvent{"sixth": nil},
 			manifest: `invalid manifest`, // This will fail if partial is not skipped.
-		}, {
+		},
+		{
 			// Regression test: files with no content should be skipped.
 			name:     []string{"seventh"},
 			path:     "seven",
@@ -130,6 +135,19 @@ metadata:
   name: example-test
   annotations:
     "helm.sh/hook": test
+`,
+		},
+		{
+			name:  []string{"ninth"},
+			path:  "nine",
+			kind:  []string{"ReplicaSet"},
+			hooks: map[string][]release.HookEvent{"ninth": {release.HookPreReady}},
+			manifest: `kind: ReplicaSet
+apiVersion: v1beta1
+metadata:
+  name: ninth
+  annotations:
+    "helm.sh/hook": pre-ready
 `,
 		},
 	}
@@ -149,8 +167,8 @@ metadata:
 		t.Errorf("Expected 2 generic manifests, got %d", len(generic))
 	}
 
-	if len(hs) != 4 {
+	if len(hs) != 5 {
-		t.Errorf("Expected 4 hooks, got %d", len(hs))
+		t.Errorf("Expected 5 hooks, got %d", len(hs))
 	}
 
 	for _, out := range hs {