Vault CA bugfixes (#19285)

* Re-add retry logic to Vault token renewal

* Fix goroutine leak

* Add test for detecting goroutine leak

* Add changelog

* Rename tests

* Add comment

.changelog/19285.txt

@@ -0,0 +1,7 @@
+```release-note:bug
+ca: Fix bug with Vault CA provider where token renewal goroutines could leak if CA failed to initialize.
+```
+
+```release-note:bug
+ca: Fix bug with Vault CA provider where renewing a retracted token would cause retries in a tight loop, degrading performance.
+```

agent/connect/ca/provider_vault.go

@@ -20,6 +20,7 @@ import (
 	"github.com/hashicorp/consul/agent/structs"
 	"github.com/hashicorp/consul/lib"
 	"github.com/hashicorp/consul/lib/decode"
+	"github.com/hashicorp/consul/lib/retry"
 )
 
 const (
@@ -175,11 +176,17 @@ func (v *VaultProvider) Configure(cfg ProviderConfig) error {
 			v.stopWatcher()
 		}
 		v.stopWatcher = cancel
+		// NOTE: Any codepaths after v.renewToken(...) which return an error
+		// _must_ call v.stopWatcher() to prevent the renewal goroutine from
+		// leaking when the CA initialization fails and gets retried later.
 		go v.renewToken(ctx, lifetimeWatcher)
 	}
 
 	// Update the intermediate (managed) PKI mount and role
 	if err := v.setupIntermediatePKIPath(); err != nil {
+		if v.stopWatcher != nil {
+			v.stopWatcher()
+		}
 		return err
 	}
 
@@ -221,6 +228,16 @@ func (v *VaultProvider) renewToken(ctx context.Context, watcher *vaultapi.Lifeti
 	go watcher.Start()
 	defer watcher.Stop()
 
+	// These values are chosen to start the exponential backoff
+	// immediately. Since the Vault client implements its own
+	// retries, this retry is mostly to avoid resource contention
+	// and log spam.
+	retrier := retry.Waiter{
+		MinFailures: 1,
+		MinWait:     1 * time.Second,
+		Jitter:      retry.NewJitter(20),
+	}
+
 	for {
 		select {
 		case <-ctx.Done():
@@ -229,7 +246,16 @@ func (v *VaultProvider) renewToken(ctx context.Context, watcher *vaultapi.Lifeti
 		case err := <-watcher.DoneCh():
 			// Watcher has stopped
 			if err != nil {
-				v.logger.Error("Error renewing token for Vault provider", "error", err)
+				v.logger.Error("Error renewing token for Vault provider", "error", err, "retries", retrier.Failures())
+			}
+
+			// Although the vault watcher has its own retry logic, we have encountered
+			// issues when passing an invalid Vault token which would send an error to
+			// watcher.DoneCh() immediately, causing us to start the watcher over and
+			// over again in a very tight loop.
+			if err := retrier.Wait(ctx); err != nil {
+				// only possible error is when context is cancelled
+				return
 			}
 
 			// If the watcher has exited and auth method is enabled,
@@ -263,6 +289,7 @@ func (v *VaultProvider) renewToken(ctx context.Context, watcher *vaultapi.Lifeti
 			go watcher.Start()
 
 		case <-watcher.RenewCh():
+			retrier.Reset()
 			v.logger.Info("Successfully renewed token for Vault provider")
 		}
 	}

agent/connect/ca/provider_vault_test.go

@@ -5,6 +5,9 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"runtime/pprof"
+	"strconv"
+	"strings"
 	"sync/atomic"
 	"testing"
 	"time"
@@ -220,8 +223,69 @@ func TestVaultCAProvider_Configure(t *testing.T) {
 			testcase.expectedValue(t, provider)
 		})
 	}
+}
+
+// This test must not run in parallel
+func TestVaultCAProvider_ConfigureFailureGoroutineLeakCheck(t *testing.T) {
+	if testing.Short() {
+		t.Skip("too slow for testing.Short")
+	}
+	SkipIfVaultNotPresent(t)
+
+	testVault := NewTestVaultServer(t)
+
+	attr := &VaultTokenAttributes{
+		RootPath:         "pki-root",
+		IntermediatePath: "pki-intermediate",
+		ConsulManaged:    true,
+	}
+	token := CreateVaultTokenWithAttrs(t, testVault.client, attr)
+
+	provider := NewVaultProvider(hclog.New(&hclog.LoggerOptions{Name: "ca.vault"}))
+
+	t.Run("error on Configure does not leak renewal routine", func(t *testing.T) {
+		config := map[string]any{
+			"RootPKIPath":         "pki-root/",
+			"IntermediatePKIPath": "badbadbad/",
+		}
+		cfg := vaultProviderConfig(t, testVault.Addr, token, config)
+
+		err := provider.Configure(cfg)
+		require.Error(t, err)
+
+		retry.RunWith(retry.TwoSeconds(), t, func(r *retry.R) {
+			profile := pprof.Lookup("goroutine")
+			sb := strings.Builder{}
+			require.NoError(r, profile.WriteTo(&sb, 2))
+			require.NotContains(r, sb.String(),
+				"created by github.com/hashicorp/consul/agent/connect/ca.(*VaultProvider).Configure",
+				"found renewal goroutine leak")
+			// If this test is failing because you added a new goroutine to
+			// (*VaultProvider).Configure AND that goroutine should persist
+			// even if Configure errored, then you should change the checked
+			// string to (*VaultProvider).renewToken.
+		})
+	})
 
-	return
+	t.Run("successful Configure starts renewal routine", func(t *testing.T) {
+		config := map[string]any{
+			"RootPKIPath":         "pki-root/",
+			"IntermediatePKIPath": "pki-intermediate/",
+		}
+		cfg := vaultProviderConfig(t, testVault.Addr, token, config)
+
+		require.NoError(t, provider.Configure(cfg))
+
+		retry.RunWith(retry.TwoSeconds(), t, func(r *retry.R) {
+			profile := pprof.Lookup("goroutine")
+			sb := strings.Builder{}
+			require.NoError(r, profile.WriteTo(&sb, 2))
+			t.Log(sb.String())
+			require.Contains(r, sb.String(),
+				"created by github.com/hashicorp/consul/agent/connect/ca.(*VaultProvider).Configure",
+				"expected renewal goroutine, got none")
+		})
+	})
 }
 
 func TestVaultCAProvider_SecondaryActiveIntermediate(t *testing.T) {