Backport of CSI: retry claims from client into release/1.2.x

.changelog/12113.txt

@@ -0,0 +1,7 @@
+```release-note:bug
+csi: Fixed a bug where allocations with volume claims would fail their first placement after a reschedule
+```
+
+```release-note:bug
+csi: Fixed a bug where allocations with volume claims would fail to restore after a client restart
+```

client/allocrunner/csi_hook.go

@@ -3,6 +3,7 @@ package allocrunner
 import (
 	"context"
 	"fmt"
+	"strings"
 	"sync"
 	"time"
 
@@ -28,6 +29,7 @@ type csiHook struct {
 	nodeSecret           string
 
 	volumeRequests     map[string]*volumeAndRequest
+	minBackoffInterval time.Duration
 	maxBackoffInterval time.Duration
 	maxBackoffDuration time.Duration
 }
@@ -47,6 +49,7 @@ func newCSIHook(alloc *structs.Allocation, logger hclog.Logger, csi csimanager.M
 		updater:              updater,
 		nodeSecret:           nodeSecret,
 		volumeRequests:       map[string]*volumeAndRequest{},
+		minBackoffInterval:   time.Second,
 		maxBackoffInterval:   time.Minute,
 		maxBackoffDuration:   time.Hour * 24,
 	}
@@ -213,11 +216,10 @@ func (c *csiHook) claimVolumesFromAlloc() (map[string]*volumeAndRequest, error)
 			},
 		}
 
-		var resp structs.CSIVolumeClaimResponse
-		if err := c.rpcClient.RPC("CSIVolume.Claim", req, &resp); err != nil {
+		resp, err := c.claimWithRetry(req)
+		if err != nil {
 			return nil, fmt.Errorf("could not claim volume %s: %w", req.VolumeID, err)
 		}
-
 		if resp.Volume == nil {
 			return nil, fmt.Errorf("Unexpected nil volume returned for ID: %v", pair.request.Source)
 		}
@@ -230,6 +232,74 @@ func (c *csiHook) claimVolumesFromAlloc() (map[string]*volumeAndRequest, error)
 	return result, nil
 }
 
+// claimWithRetry tries to claim the volume on the server, retrying
+// with exponential backoff capped to a maximum interval
+func (c *csiHook) claimWithRetry(req *structs.CSIVolumeClaimRequest) (*structs.CSIVolumeClaimResponse, error) {
+
+	// note: allocrunner hooks don't have access to the client's
+	// shutdown context, just the allocrunner's shutdown; if we make
+	// it available in the future we should thread it through here so
+	// that retry can exit gracefully instead of dropping the
+	// in-flight goroutine
+	ctx, cancel := context.WithTimeout(context.TODO(), c.maxBackoffDuration)
+	defer cancel()
+
+	var resp structs.CSIVolumeClaimResponse
+	var err error
+	backoff := c.minBackoffInterval
+	t, stop := helper.NewSafeTimer(0)
+	defer stop()
+	for {
+		select {
+		case <-ctx.Done():
+			return nil, err
+		case <-t.C:
+		}
+
+		err = c.rpcClient.RPC("CSIVolume.Claim", req, &resp)
+		if err == nil {
+			break
+		}
+
+		if !isRetryableClaimRPCError(err) {
+			break
+		}
+
+		if backoff < c.maxBackoffInterval {
+			backoff = backoff * 2
+			if backoff > c.maxBackoffInterval {
+				backoff = c.maxBackoffInterval
+			}
+		}
+		c.logger.Debug(
+			"volume could not be claimed because it is in use, retrying in %v", backoff)
+		t.Reset(backoff)
+	}
+	return &resp, err
+}
+
+// isRetryableClaimRPCError looks for errors where we need to retry
+// with backoff because we expect them to be eventually resolved.
+func isRetryableClaimRPCError(err error) bool {
+
+	// note: because these errors are returned via RPC which breaks error
+	// wrapping, we can't check with errors.Is and need to read the string
+	errMsg := err.Error()
+	if strings.Contains(errMsg, structs.ErrCSIVolumeMaxClaims.Error()) {
+		return true
+	}
+	if strings.Contains(errMsg, structs.ErrCSIClientRPCRetryable.Error()) {
+		return true
+	}
+	if strings.Contains(errMsg, "no servers") {
+		return true
+	}
+	if strings.Contains(errMsg, structs.ErrNoLeader.Error()) {
+		return true
+	}
+	return false
+}
+
 func (c *csiHook) shouldRun() bool {
 	tg := c.alloc.Job.LookupTaskGroup(c.alloc.TaskGroup)
 	for _, vol := range tg.Volumes {
@@ -286,7 +356,7 @@ func (c *csiHook) unmountWithRetry(pair *volumeAndRequest) error {
 	ctx, cancel := context.WithTimeout(context.TODO(), c.maxBackoffDuration)
 	defer cancel()
 	var err error
-	backoff := time.Second
+	backoff := c.minBackoffInterval
 	t, stop := helper.NewSafeTimer(0)
 	defer stop()
 	for {
@@ -307,6 +377,8 @@ func (c *csiHook) unmountWithRetry(pair *volumeAndRequest) error {
 				backoff = c.maxBackoffInterval
 			}
 		}
+		c.logger.Debug(
+			"volume could not be unmounted, retrying in %v", backoff)
 		t.Reset(backoff)
 	}
 	return nil

client/allocrunner/csi_hook_test.go

@@ -7,12 +7,14 @@ import (
 	"testing"
 	"time"
 
+	"github.com/pkg/errors"
 	"github.com/stretchr/testify/require"
 
 	"github.com/hashicorp/nomad/client/allocrunner/interfaces"
 	"github.com/hashicorp/nomad/client/pluginmanager"
 	"github.com/hashicorp/nomad/client/pluginmanager/csimanager"
 	cstructs "github.com/hashicorp/nomad/client/structs"
+	"github.com/hashicorp/nomad/helper"
 	"github.com/hashicorp/nomad/helper/testlog"
 	"github.com/hashicorp/nomad/nomad/mock"
 	"github.com/hashicorp/nomad/nomad/structs"
@@ -34,6 +36,9 @@ func TestCSIHook(t *testing.T) {
 	testcases := []struct {
 		name                   string
 		volumeRequests         map[string]*structs.VolumeRequest
+		startsUnschedulable    bool
+		startsWithClaims       bool
+		expectedClaimErr       error
 		expectedMounts         map[string]*csimanager.MountInfo
 		expectedMountCalls     int
 		expectedUnmountCalls   int
@@ -89,6 +94,58 @@ func TestCSIHook(t *testing.T) {
 			expectedUnpublishCalls: 1,
 		},
 
+		{
+			name: "fatal error on claim",
+			volumeRequests: map[string]*structs.VolumeRequest{
+				"vol0": {
+					Name:           "vol0",
+					Type:           structs.VolumeTypeCSI,
+					Source:         "testvolume0",
+					ReadOnly:       true,
+					AccessMode:     structs.CSIVolumeAccessModeSingleNodeReader,
+					AttachmentMode: structs.CSIVolumeAttachmentModeFilesystem,
+					MountOptions:   &structs.CSIMountOptions{},
+					PerAlloc:       false,
+				},
+			},
+			startsUnschedulable: true,
+			expectedMounts: map[string]*csimanager.MountInfo{
+				"vol0": &csimanager.MountInfo{Source: fmt.Sprintf(
+					"test-alloc-dir/%s/testvolume0/ro-file-system-single-node-reader-only", alloc.ID)},
+			},
+			expectedMountCalls:     0,
+			expectedUnmountCalls:   0,
+			expectedClaimCalls:     1,
+			expectedUnpublishCalls: 0,
+			expectedClaimErr: errors.New(
+				"claim volumes: could not claim volume testvolume0: volume is currently unschedulable"),
+		},
+
+		{
+			name: "retryable error on claim",
+			volumeRequests: map[string]*structs.VolumeRequest{
+				"vol0": {
+					Name:           "vol0",
+					Type:           structs.VolumeTypeCSI,
+					Source:         "testvolume0",
+					ReadOnly:       true,
+					AccessMode:     structs.CSIVolumeAccessModeSingleNodeReader,
+					AttachmentMode: structs.CSIVolumeAttachmentModeFilesystem,
+					MountOptions:   &structs.CSIMountOptions{},
+					PerAlloc:       false,
+				},
+			},
+			startsWithClaims: true,
+			expectedMounts: map[string]*csimanager.MountInfo{
+				"vol0": &csimanager.MountInfo{Source: fmt.Sprintf(
+					"test-alloc-dir/%s/testvolume0/ro-file-system-single-node-reader-only", alloc.ID)},
+			},
+			expectedMountCalls:     1,
+			expectedUnmountCalls:   1,
+			expectedClaimCalls:     2,
+			expectedUnpublishCalls: 1,
+		},
+
 		// TODO: this won't actually work on the client.
 		// https://github.com/hashicorp/nomad/issues/11798
 		//
@@ -136,7 +193,12 @@ func TestCSIHook(t *testing.T) {
 
 			callCounts := map[string]int{}
 			mgr := mockPluginManager{mounter: mockVolumeMounter{callCounts: callCounts}}
-			rpcer := mockRPCer{alloc: alloc, callCounts: callCounts}
+			rpcer := mockRPCer{
+				alloc:            alloc,
+				callCounts:       callCounts,
+				hasExistingClaim: helper.BoolToPtr(tc.startsWithClaims),
+				schedulable:      helper.BoolToPtr(!tc.startsUnschedulable),
+			}
 			ar := mockAllocRunner{
 				res: &cstructs.AllocHookResources{},
 				caps: &drivers.Capabilities{
@@ -145,17 +207,24 @@ func TestCSIHook(t *testing.T) {
 				},
 			}
 			hook := newCSIHook(alloc, logger, mgr, rpcer, ar, ar, "secret")
-			hook.maxBackoffInterval = 100 * time.Millisecond
-			hook.maxBackoffDuration = 2 * time.Second
+			hook.minBackoffInterval = 1 * time.Millisecond
+			hook.maxBackoffInterval = 10 * time.Millisecond
+			hook.maxBackoffDuration = 500 * time.Millisecond
 
 			require.NotNil(t, hook)
 
-			require.NoError(t, hook.Prerun())
-			mounts := ar.GetAllocHookResources().GetCSIMounts()
-			require.NotNil(t, mounts)
-			require.Equal(t, tc.expectedMounts, mounts)
+			if tc.expectedClaimErr != nil {
+				require.EqualError(t, hook.Prerun(), tc.expectedClaimErr.Error())
+				mounts := ar.GetAllocHookResources().GetCSIMounts()
+				require.Nil(t, mounts)
+			} else {
+				require.NoError(t, hook.Prerun())
+				mounts := ar.GetAllocHookResources().GetCSIMounts()
+				require.NotNil(t, mounts)
+				require.Equal(t, tc.expectedMounts, mounts)
+				require.NoError(t, hook.Postrun())
+			}
 
-			require.NoError(t, hook.Postrun())
 			require.Equal(t, tc.expectedMountCalls, callCounts["mount"])
 			require.Equal(t, tc.expectedUnmountCalls, callCounts["unmount"])
 			require.Equal(t, tc.expectedClaimCalls, callCounts["claim"])
@@ -168,25 +237,11 @@ func TestCSIHook(t *testing.T) {
 
 // HELPERS AND MOCKS
 
-func testVolume(id string) *structs.CSIVolume {
-	vol := structs.NewCSIVolume(id, 0)
-	vol.Schedulable = true
-	vol.RequestedCapabilities = []*structs.CSIVolumeCapability{
-		{
-			AttachmentMode: structs.CSIVolumeAttachmentModeFilesystem,
-			AccessMode:     structs.CSIVolumeAccessModeSingleNodeReader,
-		},
-		{
-			AttachmentMode: structs.CSIVolumeAttachmentModeFilesystem,
-			AccessMode:     structs.CSIVolumeAccessModeSingleNodeWriter,
-		},
-	}
-	return vol
-}
-
 type mockRPCer struct {
-	alloc      *structs.Allocation
-	callCounts map[string]int
+	alloc            *structs.Allocation
+	callCounts       map[string]int
+	hasExistingClaim *bool
+	schedulable      *bool
 }
 
 // RPC mocks the server RPCs, acting as though any request succeeds
@@ -195,7 +250,7 @@ func (r mockRPCer) RPC(method string, args interface{}, reply interface{}) error
 	case "CSIVolume.Claim":
 		r.callCounts["claim"]++
 		req := args.(*structs.CSIVolumeClaimRequest)
-		vol := testVolume(req.VolumeID)
+		vol := r.testVolume(req.VolumeID)
 		err := vol.Claim(req.ToClaim(), r.alloc)
 		if err != nil {
 			return err
@@ -215,6 +270,44 @@ func (r mockRPCer) RPC(method string, args interface{}, reply interface{}) error
 	return nil
 }
 
+// testVolume is a helper that optionally starts as unschedulable /
+// claimed until after the first claim RPC is made, so that we can
+// test retryable vs non-retryable failures
+func (r mockRPCer) testVolume(id string) *structs.CSIVolume {
+	vol := structs.NewCSIVolume(id, 0)
+	vol.Schedulable = *r.schedulable
+	vol.RequestedCapabilities = []*structs.CSIVolumeCapability{
+		{
+			AttachmentMode: structs.CSIVolumeAttachmentModeFilesystem,
+			AccessMode:     structs.CSIVolumeAccessModeSingleNodeReader,
+		},
+		{
+			AttachmentMode: structs.CSIVolumeAttachmentModeFilesystem,
+			AccessMode:     structs.CSIVolumeAccessModeSingleNodeWriter,
+		},
+	}
+
+	if *r.hasExistingClaim {
+		vol.AccessMode = structs.CSIVolumeAccessModeSingleNodeReader
+		vol.AttachmentMode = structs.CSIVolumeAttachmentModeFilesystem
+		vol.ReadClaims["another-alloc-id"] = &structs.CSIVolumeClaim{
+			AllocationID:   "another-alloc-id",
+			NodeID:         "another-node-id",
+			Mode:           structs.CSIVolumeClaimRead,
+			AccessMode:     structs.CSIVolumeAccessModeSingleNodeReader,
+			AttachmentMode: structs.CSIVolumeAttachmentModeFilesystem,
+			State:          structs.CSIVolumeClaimStateTaken,
+		}
+	}
+
+	if r.callCounts["claim"] >= 0 {
+		*r.hasExistingClaim = false
+		*r.schedulable = true
+	}
+
+	return vol
+}
+
 type mockVolumeMounter struct {
 	callCounts map[string]int
 }