[feature] Initial Prometheus metrics implementation (#2334)

* feat: Initial OTEL metrics

* docs: add metrics documentation

* fix: metrics endpoint conditional check

* feat: metrics endpoint basic auth

* fix: make metrics-auth-enabled default false

* fix: go fmt helpers.gen.go

* fix: add metric-related env vars to envparsing.sh

* fix: metrics docs

* fix: metrics related stuff in envparsing.sh

* fix: metrics docs

* chore: metrics docs wording

* fix: metrics stuff in envparsing?

* bump otel versions

---------

Co-authored-by: Tsuribori <user@acertaindebian>
Co-authored-by: Tsuribori <none@example.org>
Co-authored-by: tsmethurst <tobi.smethurst@protonmail.com>

1 files changed, 132 insertions, 0 deletions

diff --git a/vendor/github.com/prometheus/procfs/proc_fdinfo.go b/vendor/github.com/prometheus/procfs/proc_fdinfo.go
new file mode 100644
index 000000000..4b7933e4f
--- /dev/null
+++ b/vendor/github.com/prometheus/procfs/proc_fdinfo.go
@@ -0,0 +1,132 @@
+// Copyright 2019 The Prometheus Authors
+// 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.
+
+package procfs
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"regexp"
+
+	"github.com/prometheus/procfs/internal/util"
+)
+
+var (
+	rPos          = regexp.MustCompile(`^pos:\s+(\d+)$`)
+	rFlags        = regexp.MustCompile(`^flags:\s+(\d+)$`)
+	rMntID        = regexp.MustCompile(`^mnt_id:\s+(\d+)$`)
+	rInotify      = regexp.MustCompile(`^inotify`)
+	rInotifyParts = regexp.MustCompile(`^inotify\s+wd:([0-9a-f]+)\s+ino:([0-9a-f]+)\s+sdev:([0-9a-f]+)(?:\s+mask:([0-9a-f]+))?`)
+)
+
+// ProcFDInfo contains represents file descriptor information.
+type ProcFDInfo struct {
+	// File descriptor
+	FD string
+	// File offset
+	Pos string
+	// File access mode and status flags
+	Flags string
+	// Mount point ID
+	MntID string
+	// List of inotify lines (structured) in the fdinfo file (kernel 3.8+ only)
+	InotifyInfos []InotifyInfo
+}
+
+// FDInfo constructor. On kernels older than 3.8, InotifyInfos will always be empty.
+func (p Proc) FDInfo(fd string) (*ProcFDInfo, error) {
+	data, err := util.ReadFileNoStat(p.path("fdinfo", fd))
+	if err != nil {
+		return nil, err
+	}
+
+	var text, pos, flags, mntid string
+	var inotify []InotifyInfo
+
+	scanner := bufio.NewScanner(bytes.NewReader(data))
+	for scanner.Scan() {
+		text = scanner.Text()
+		if rPos.MatchString(text) {
+			pos = rPos.FindStringSubmatch(text)[1]
+		} else if rFlags.MatchString(text) {
+			flags = rFlags.FindStringSubmatch(text)[1]
+		} else if rMntID.MatchString(text) {
+			mntid = rMntID.FindStringSubmatch(text)[1]
+		} else if rInotify.MatchString(text) {
+			newInotify, err := parseInotifyInfo(text)
+			if err != nil {
+				return nil, err
+			}
+			inotify = append(inotify, *newInotify)
+		}
+	}
+
+	i := &ProcFDInfo{
+		FD:           fd,
+		Pos:          pos,
+		Flags:        flags,
+		MntID:        mntid,
+		InotifyInfos: inotify,
+	}
+
+	return i, nil
+}
+
+// InotifyInfo represents a single inotify line in the fdinfo file.
+type InotifyInfo struct {
+	// Watch descriptor number
+	WD string
+	// Inode number
+	Ino string
+	// Device ID
+	Sdev string
+	// Mask of events being monitored
+	Mask string
+}
+
+// InotifyInfo constructor. Only available on kernel 3.8+.
+func parseInotifyInfo(line string) (*InotifyInfo, error) {
+	m := rInotifyParts.FindStringSubmatch(line)
+	if len(m) >= 4 {
+		var mask string
+		if len(m) == 5 {
+			mask = m[4]
+		}
+		i := &InotifyInfo{
+			WD:   m[1],
+			Ino:  m[2],
+			Sdev: m[3],
+			Mask: mask,
+		}
+		return i, nil
+	}
+	return nil, fmt.Errorf("%w: invalid inode entry: %q", ErrFileParse, line)
+}
+
+// ProcFDInfos represents a list of ProcFDInfo structs.
+type ProcFDInfos []ProcFDInfo
+
+func (p ProcFDInfos) Len() int           { return len(p) }
+func (p ProcFDInfos) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+func (p ProcFDInfos) Less(i, j int) bool { return p[i].FD < p[j].FD }
+
+// InotifyWatchLen returns the total number of inotify watches.
+func (p ProcFDInfos) InotifyWatchLen() (int, error) {
+	length := 0
+	for _, f := range p {
+		length += len(f.InotifyInfos)
+	}
+
+	return length, nil
+}