misc: fuse fs for the stats segment

This extra allows to mount a FUSE filesystem reflecting
the state of the stats segment.

Type: feature

Signed-off-by: Arthur de Kerhor <arthurdekerhor@gmail.com>
Change-Id: I692f9ca5a65c1123b3cf28c761455eec36049791

1 files changed, 207 insertions, 0 deletions

diff --git a/extras/vpp_stats_fs/stats_fs.go b/extras/vpp_stats_fs/stats_fs.go
new file mode 100644
index 00000000000..a9b8ae77633
--- /dev/null
+++ b/extras/vpp_stats_fs/stats_fs.go
@@ -0,0 +1,207 @@
+/*
+ * Copyright (c) 2021 Cisco Systems and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*Go-FUSE allows us to define the behaviour of our filesystem by recoding any primitive function we need.
+ *The structure of the filesystem is constructed as a tree.
+ *Each type of nodes (root, directory, file) follows its own prmitives.
+ */
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"path/filepath"
+	"strings"
+	"syscall"
+	"time"
+
+	"github.com/hanwen/go-fuse/v2/fs"
+	"github.com/hanwen/go-fuse/v2/fuse"
+
+	"git.fd.io/govpp.git/adapter"
+	"git.fd.io/govpp.git/adapter/statsclient"
+)
+
+func updateDir(ctx context.Context, n *fs.Inode, cl *statsclient.StatsClient, dirPath string) syscall.Errno {
+	list, err := cl.ListStats(dirPath)
+	if err != nil {
+		log.Println("list stats failed:", err)
+		return syscall.EAGAIN
+	}
+
+	if list == nil {
+		n.ForgetPersistent()
+		return syscall.ENOENT
+	}
+
+	for _, path := range list {
+		localPath := strings.TrimPrefix(path, dirPath)
+		dir, base := filepath.Split(localPath)
+
+		parent := n
+		for _, component := range strings.Split(dir, "/") {
+			if len(component) == 0 {
+				continue
+			}
+			child := parent.GetChild(component)
+			if child == nil {
+				child = parent.NewPersistentInode(ctx, &dirNode{client: cl, lastUpdate: time.Now()},
+					fs.StableAttr{Mode: fuse.S_IFDIR})
+				parent.AddChild(component, child, true)
+			}
+
+			parent = child
+		}
+		filename := strings.Replace(base, " ", "_", -1)
+		child := parent.GetChild(filename)
+		if child == nil {
+			child := parent.NewPersistentInode(ctx, &statNode{client: cl, path: path}, fs.StableAttr{})
+			parent.AddChild(filename, child, true)
+		}
+	}
+	return 0
+}
+
+func getCounterContent(path string, client *statsclient.StatsClient) (content string, status syscall.Errno) {
+	content = ""
+	//We add '$' because we deal with regexp here
+	res, err := client.DumpStats(path + "$")
+	if err != nil {
+		return content, syscall.EAGAIN
+	}
+	if res == nil {
+		return content, syscall.ENOENT
+	}
+
+	result := res[0]
+	if result.Data == nil {
+		return content, 0
+	}
+
+	switch result.Type {
+	case adapter.ScalarIndex:
+		stats := result.Data.(adapter.ScalarStat)
+		content = fmt.Sprintf("%.2f\n", stats)
+	case adapter.ErrorIndex:
+		stats := result.Data.(adapter.ErrorStat)
+		content = fmt.Sprintf("%-16s%s\n", "Index", "Count")
+		for i, value := range stats {
+			content += fmt.Sprintf("%-16d%d\n", i, value)
+		}
+	case adapter.SimpleCounterVector:
+		stats := result.Data.(adapter.SimpleCounterStat)
+		content = fmt.Sprintf("%-16s%-16s%s\n", "Thread", "Index", "Packets")
+		for i, vector := range stats {
+			for j, value := range vector {
+				content += fmt.Sprintf("%-16d%-16d%d\n", i, j, value)
+			}
+		}
+	case adapter.CombinedCounterVector:
+		stats := result.Data.(adapter.CombinedCounterStat)
+		content = fmt.Sprintf("%-16s%-16s%-16s%s\n", "Thread", "Index", "Packets", "Bytes")
+		for i, vector := range stats {
+			for j, value := range vector {
+				content += fmt.Sprintf("%-16d%-16d%-16d%d\n", i, j, value[0], value[1])
+			}
+		}
+	case adapter.NameVector:
+		stats := result.Data.(adapter.NameStat)
+		content = fmt.Sprintf("%-16s%s\n", "Index", "Name")
+		for i, value := range stats {
+			content += fmt.Sprintf("%-16d%s\n", i, string(value))
+		}
+	default:
+		content = fmt.Sprintf("Unknown stat type: %d\n", result.Type)
+		//For now, the empty type (file deleted) is not implemented in GoVPP
+		return content, syscall.ENOENT
+	}
+	return content, fs.OK
+}
+
+type rootNode struct {
+	fs.Inode
+	client     *statsclient.StatsClient
+	lastUpdate time.Time
+}
+
+var _ = (fs.NodeOnAdder)((*rootNode)(nil))
+
+func (root *rootNode) OnAdd(ctx context.Context) {
+	updateDir(ctx, &root.Inode, root.client, "/")
+	root.lastUpdate = time.Now()
+}
+
+//The dirNode structure represents directories
+type dirNode struct {
+	fs.Inode
+	client     *statsclient.StatsClient
+	lastUpdate time.Time
+}
+
+var _ = (fs.NodeOpendirer)((*dirNode)(nil))
+
+func (dn *dirNode) Opendir(ctx context.Context) syscall.Errno {
+	//We do not update a directory more than once a second, as counters are rarely added/deleted.
+	if time.Now().Sub(dn.lastUpdate) < time.Second {
+		return 0
+	}
+
+	//directoryPath is the path to the current directory from root
+	directoryPath := "/" + dn.Inode.Path(nil) + "/"
+	status := updateDir(ctx, &dn.Inode, dn.client, directoryPath)
+	dn.lastUpdate = time.Now()
+	return status
+}
+
+//The statNode structure represents counters
+type statNode struct {
+	fs.Inode
+	client *statsclient.StatsClient
+	path   string
+}
+
+var _ = (fs.NodeOpener)((*statNode)(nil))
+
+//When a file is opened, the correpsonding counter value is dumped and a file handle is created
+func (sn *statNode) Open(ctx context.Context, flags uint32) (fs.FileHandle, uint32, syscall.Errno) {
+	content, status := getCounterContent(sn.path, sn.client)
+	if status == syscall.ENOENT {
+		sn.Inode.ForgetPersistent()
+	}
+	return &statFH{data: []byte(content)}, fuse.FOPEN_DIRECT_IO, status
+}
+
+/* The statFH structure aims at dislaying the counters dynamically.
+ * It allows the Kernel to read data as I/O without having to specify files sizes, as they may evolve dynamically.
+ */
+type statFH struct {
+	data []byte
+}
+
+var _ = (fs.FileReader)((*statFH)(nil))
+
+func (fh *statFH) Read(ctx context.Context, data []byte, off int64) (fuse.ReadResult, syscall.Errno) {
+	end := int(off) + len(data)
+	if end > len(fh.data) {
+		end = len(fh.data)
+	}
+	return fuse.ReadResultData(fh.data[off:end]), fs.OK
+}
+
+//NewStatsFileSystem creates the fs for the stat segment.
+func NewStatsFileSystem(sc *statsclient.StatsClient) (root fs.InodeEmbedder, err error) {
+	return &rootNode{client: sc}, nil
+}