statsclient: added symlinks

Symlink support based on https://gerrit.fd.io/r/c/vpp/+/31636

Added new stat types `CounterStat` and `CombinedCounterStat` which
represent simple/combined value of a single item (interface, node)
as a array of values by workers.

Example:
/if/names                      NameVector [local0 tap0 tap1]
/if/ip6               SimpleCounterVector [[0 9 0] [0 25 3] [0 0 60] [0 0 0]]
/interfaces/tap0/ip6  SimpleCounterVector [[9] [25] [0] [0]]
/interfaces/tap1/ip6  SimpleCounterVector [[0] [3] [60] [0]]

Field `Symlink` added to StatEntry to mark symlink stats.

For stats v2 only

Change-Id: Iadc825f3c42b05bfc9a91462dba8a0b0068c7cd6
Signed-off-by: Vladimir Lavor <vlavor@cisco.com>

4 files changed, 82 insertions, 16 deletions

diff --git a/adapter/statsclient/stat_segment_api.go b/adapter/statsclient/stat_segment_api.go
index 23755a5..2161e6e 100644
--- a/adapter/statsclient/stat_segment_api.go
+++ b/adapter/statsclient/stat_segment_api.go
@@ -46,6 +46,7 @@ const (
 	statDirErrorIndex            = 4
 	statDirNameVector            = 5
 	statDirEmpty                 = 6
+	statDirSymlink               = 7
 )
 
 type (
@@ -75,8 +76,10 @@ type statSegment interface {
 	GetEpoch() (int64, bool)
 
 	// CopyEntryData accepts pointer to a directory segment and returns adapter.Stat
-	// based on directory type populated with data
-	CopyEntryData(segment dirSegment) adapter.Stat
+	// based on directory type populated with data. The index is an optional parameter
+	// (used by symlinks) returning stats for item on the given index only.
+	// Use ^uint32(0) as an empty index (since 0 is a valid value).
+	CopyEntryData(segment dirSegment, index uint32) adapter.Stat
 
 	// UpdateEntryData accepts pointer to a directory segment with data, and stat
 	// segment to update
diff --git a/adapter/statsclient/statsclient.go b/adapter/statsclient/statsclient.go
index 16af16a..0b16a77 100644
--- a/adapter/statsclient/statsclient.go
+++ b/adapter/statsclient/statsclient.go
@@ -505,13 +505,15 @@ func (sc *StatsClient) getStatEntriesOnIndex(vector dirVector, indexes ...uint32
 		if len(dirName) == 0 {
 			return
 		}
+		d := sc.CopyEntryData(dirPtr, ^uint32(0))
 		entries = append(entries, adapter.StatEntry{
 			StatIdentifier: adapter.StatIdentifier{
 				Index: index,
 				Name:  dirName,
 			},
-			Type: adapter.StatType(dirType),
-			Data: sc.CopyEntryData(dirPtr),
+			Type:    d.Type(),
+			Data:    d,
+			Symlink: adapter.StatType(dirType) == adapter.Symlink,
 		})
 	}
 	return entries, nil
diff --git a/adapter/statsclient/statseg_v1.go b/adapter/statsclient/statseg_v1.go
index e9e8331..efd487e 100644
--- a/adapter/statsclient/statseg_v1.go
+++ b/adapter/statsclient/statseg_v1.go
@@ -93,7 +93,7 @@ func (ss *statSegmentV1) GetEpoch() (int64, bool) {
 	return sh.epoch, sh.inProgress != 0
 }
 
-func (ss *statSegmentV1) CopyEntryData(segment dirSegment) adapter.Stat {
+func (ss *statSegmentV1) CopyEntryData(segment dirSegment, _ uint32) adapter.Stat {
 	dirEntry := (*statSegDirectoryEntryV1)(segment)
 	dirType := adapter.StatType(dirEntry.directoryType)
 
@@ -214,6 +214,9 @@ func (ss *statSegmentV1) CopyEntryData(segment dirSegment) adapter.Stat {
 	case statDirEmpty:
 		// no-op
 
+	case statDirSymlink:
+		debugf("Symlinks are not supported for stats v1")
+
 	default:
 		// TODO: monitor occurrences with metrics
 		debugf("Unknown type %d for stat entry: %q", dirEntry.directoryType, dirEntry.name)
diff --git a/adapter/statsclient/statseg_v2.go b/adapter/statsclient/statseg_v2.go
index 10bc5f5..16f1729 100644
--- a/adapter/statsclient/statseg_v2.go
+++ b/adapter/statsclient/statseg_v2.go
@@ -15,6 +15,8 @@
 package statsclient
 
 import (
+	"bytes"
+	"encoding/binary"
 	"sync/atomic"
 	"unsafe"
 
@@ -38,6 +40,7 @@ type sharedHeaderV2 struct {
 type statSegDirectoryEntryV2 struct {
 	directoryType dirType
 	// unionData can represent:
+	// - symlink indexes
 	// - index
 	// - value
 	// - pointer to data
@@ -87,7 +90,7 @@ func (ss *statSegmentV2) GetEpoch() (int64, bool) {
 	return sh.epoch, sh.inProgress != 0
 }
 
-func (ss *statSegmentV2) CopyEntryData(segment dirSegment) adapter.Stat {
+func (ss *statSegmentV2) CopyEntryData(segment dirSegment, index uint32) adapter.Stat {
 	dirEntry := (*statSegDirectoryEntryV2)(segment)
 	if dirEntry.unionData == 0 {
 		debugf("data value or pointer not defined for %s", dirEntry.name)
@@ -135,11 +138,21 @@ func (ss *statSegmentV2) CopyEntryData(segment dirSegment) adapter.Stat {
 				continue
 			}
 			counterVectorLength := *(*uint32)(vectorLen(counterVector))
-			data[i] = make([]adapter.Counter, counterVectorLength)
-			for j := uint32(0); j < counterVectorLength; j++ {
-				offset := uintptr(j) * unsafe.Sizeof(adapter.Counter(0))
-				val := *(*adapter.Counter)(statSegPointer(counterVector, offset))
-				data[i][j] = val
+			if index == ^uint32(0) {
+				data[i] = make([]adapter.Counter, counterVectorLength)
+				for j := uint32(0); j < counterVectorLength; j++ {
+					offset := uintptr(j) * unsafe.Sizeof(adapter.Counter(0))
+					data[i][j] = *(*adapter.Counter)(statSegPointer(counterVector, offset))
+				}
+			} else {
+				data[i] = make([]adapter.Counter, 1) // expect single value
+				for j := uint32(0); j < counterVectorLength; j++ {
+					offset := uintptr(j) * unsafe.Sizeof(adapter.Counter(0))
+					if index == j {
+						data[i][0] = *(*adapter.Counter)(statSegPointer(counterVector, offset))
+						break
+					}
+				}
 			}
 		}
 		return adapter.SimpleCounterStat(data)
@@ -160,11 +173,21 @@ func (ss *statSegmentV2) CopyEntryData(segment dirSegment) adapter.Stat {
 				continue
 			}
 			counterVectorLength := *(*uint32)(vectorLen(counterVector))
-			data[i] = make([]adapter.CombinedCounter, counterVectorLength)
-			for j := uint32(0); j < counterVectorLength; j++ {
-				offset := uintptr(j) * unsafe.Sizeof(adapter.CombinedCounter{})
-				val := *(*adapter.CombinedCounter)(statSegPointer(counterVector, offset))
-				data[i][j] = val
+			if index == ^uint32(0) {
+				data[i] = make([]adapter.CombinedCounter, counterVectorLength)
+				for j := uint32(0); j < counterVectorLength; j++ {
+					offset := uintptr(j) * unsafe.Sizeof(adapter.CombinedCounter{})
+					data[i][j] = *(*adapter.CombinedCounter)(statSegPointer(counterVector, offset))
+				}
+			} else {
+				data[i] = make([]adapter.CombinedCounter, 1) // expect single value pair
+				for j := uint32(0); j < counterVectorLength; j++ {
+					offset := uintptr(j) * unsafe.Sizeof(adapter.CombinedCounter{})
+					if index == j {
+						data[i][0] = *(*adapter.CombinedCounter)(statSegPointer(counterVector, offset))
+						break
+					}
+				}
 			}
 		}
 		return adapter.CombinedCounterStat(data)
@@ -205,6 +228,22 @@ func (ss *statSegmentV2) CopyEntryData(segment dirSegment) adapter.Stat {
 		return adapter.EmptyStat("<none>")
 		// no-op
 
+	case statDirSymlink:
+		// prevent recursion loops
+		if index != ^uint32(0) {
+			debugf("received symlink with defined item index")
+			return nil
+		}
+		i1, i2 := ss.getSymlinkIndexes(dirEntry)
+		// use first index to get the stats directory the symlink points to
+		header := ss.loadSharedHeader(ss.sharedHeader)
+		dirVector := ss.adjust(dirVector(&header.dirVector))
+		statSegDir2 := dirSegment(uintptr(dirVector) + uintptr(i1)*unsafe.Sizeof(statSegDirectoryEntryV2{}))
+
+		// retry with actual stats segment and use second index to get
+		// stats for the required item
+		return ss.CopyEntryData(statSegDir2, i2)
+
 	default:
 		// TODO: monitor occurrences with metrics
 		debugf("Unknown type %d for stat entry: %q", dirEntry.directoryType, dirEntry.name)
@@ -349,3 +388,22 @@ func (ss *statSegmentV2) getErrorVector() dirVector {
 	header := ss.loadSharedHeader(ss.sharedHeader)
 	return ss.adjust(dirVector(&header.errorVector))
 }
+
+func (ss *statSegmentV2) getSymlinkIndexes(dirEntry *statSegDirectoryEntryV2) (index1, index2 uint32) {
+	var b bytes.Buffer
+	if err := binary.Write(&b, binary.LittleEndian, dirEntry.unionData); err != nil {
+		debugf("error getting symlink indexes for %s: %v", dirEntry.name, err)
+		return
+	}
+	if len(b.Bytes()) != 8 {
+		debugf("incorrect symlink union data length for %s: expected 8, got %d", dirEntry.name, len(b.Bytes()))
+		return
+	}
+	for i := range b.Bytes()[:4] {
+		index1 += uint32(b.Bytes()[i]) << (uint32(i) * 8)
+	}
+	for i := range b.Bytes()[4:] {
+		index2 += uint32(b.Bytes()[i+4]) << (uint32(i) * 8)
+	}
+	return
+}