[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>

5 files changed, 317 insertions, 0 deletions

diff --git a/vendor/github.com/prometheus/procfs/internal/util/parse.go b/vendor/github.com/prometheus/procfs/internal/util/parse.go
new file mode 100644
index 000000000..14272dc78
--- /dev/null
+++ b/vendor/github.com/prometheus/procfs/internal/util/parse.go
@@ -0,0 +1,112 @@
+// Copyright 2018 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 util
+
+import (
+	"os"
+	"strconv"
+	"strings"
+)
+
+// ParseUint32s parses a slice of strings into a slice of uint32s.
+func ParseUint32s(ss []string) ([]uint32, error) {
+	us := make([]uint32, 0, len(ss))
+	for _, s := range ss {
+		u, err := strconv.ParseUint(s, 10, 32)
+		if err != nil {
+			return nil, err
+		}
+
+		us = append(us, uint32(u))
+	}
+
+	return us, nil
+}
+
+// ParseUint64s parses a slice of strings into a slice of uint64s.
+func ParseUint64s(ss []string) ([]uint64, error) {
+	us := make([]uint64, 0, len(ss))
+	for _, s := range ss {
+		u, err := strconv.ParseUint(s, 10, 64)
+		if err != nil {
+			return nil, err
+		}
+
+		us = append(us, u)
+	}
+
+	return us, nil
+}
+
+// ParsePInt64s parses a slice of strings into a slice of int64 pointers.
+func ParsePInt64s(ss []string) ([]*int64, error) {
+	us := make([]*int64, 0, len(ss))
+	for _, s := range ss {
+		u, err := strconv.ParseInt(s, 10, 64)
+		if err != nil {
+			return nil, err
+		}
+
+		us = append(us, &u)
+	}
+
+	return us, nil
+}
+
+// Parses a uint64 from given hex in string.
+func ParseHexUint64s(ss []string) ([]*uint64, error) {
+	us := make([]*uint64, 0, len(ss))
+	for _, s := range ss {
+		u, err := strconv.ParseUint(s, 16, 64)
+		if err != nil {
+			return nil, err
+		}
+
+		us = append(us, &u)
+	}
+
+	return us, nil
+}
+
+// ReadUintFromFile reads a file and attempts to parse a uint64 from it.
+func ReadUintFromFile(path string) (uint64, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return 0, err
+	}
+	return strconv.ParseUint(strings.TrimSpace(string(data)), 10, 64)
+}
+
+// ReadIntFromFile reads a file and attempts to parse a int64 from it.
+func ReadIntFromFile(path string) (int64, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return 0, err
+	}
+	return strconv.ParseInt(strings.TrimSpace(string(data)), 10, 64)
+}
+
+// ParseBool parses a string into a boolean pointer.
+func ParseBool(b string) *bool {
+	var truth bool
+	switch b {
+	case "enabled":
+		truth = true
+	case "disabled":
+		truth = false
+	default:
+		return nil
+	}
+	return &truth
+}
diff --git a/vendor/github.com/prometheus/procfs/internal/util/readfile.go b/vendor/github.com/prometheus/procfs/internal/util/readfile.go
new file mode 100644
index 000000000..71b7a70eb
--- /dev/null
+++ b/vendor/github.com/prometheus/procfs/internal/util/readfile.go
@@ -0,0 +1,37 @@
+// 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 util
+
+import (
+	"io"
+	"os"
+)
+
+// ReadFileNoStat uses io.ReadAll to read contents of entire file.
+// This is similar to os.ReadFile but without the call to os.Stat, because
+// many files in /proc and /sys report incorrect file sizes (either 0 or 4096).
+// Reads a max file size of 1024kB.  For files larger than this, a scanner
+// should be used.
+func ReadFileNoStat(filename string) ([]byte, error) {
+	const maxBufferSize = 1024 * 1024
+
+	f, err := os.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	reader := io.LimitReader(f, maxBufferSize)
+	return io.ReadAll(reader)
+}
diff --git a/vendor/github.com/prometheus/procfs/internal/util/sysreadfile.go b/vendor/github.com/prometheus/procfs/internal/util/sysreadfile.go
new file mode 100644
index 000000000..1ab875cee
--- /dev/null
+++ b/vendor/github.com/prometheus/procfs/internal/util/sysreadfile.go
@@ -0,0 +1,50 @@
+// Copyright 2018 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.
+
+//go:build (linux || darwin) && !appengine
+// +build linux darwin
+// +build !appengine
+
+package util
+
+import (
+	"bytes"
+	"os"
+	"syscall"
+)
+
+// SysReadFile is a simplified os.ReadFile that invokes syscall.Read directly.
+// https://github.com/prometheus/node_exporter/pull/728/files
+//
+// Note that this function will not read files larger than 128 bytes.
+func SysReadFile(file string) (string, error) {
+	f, err := os.Open(file)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	// On some machines, hwmon drivers are broken and return EAGAIN.  This causes
+	// Go's os.ReadFile implementation to poll forever.
+	//
+	// Since we either want to read data or bail immediately, do the simplest
+	// possible read using syscall directly.
+	const sysFileBufferSize = 128
+	b := make([]byte, sysFileBufferSize)
+	n, err := syscall.Read(int(f.Fd()), b)
+	if err != nil {
+		return "", err
+	}
+
+	return string(bytes.TrimSpace(b[:n])), nil
+}
diff --git a/vendor/github.com/prometheus/procfs/internal/util/sysreadfile_compat.go b/vendor/github.com/prometheus/procfs/internal/util/sysreadfile_compat.go
new file mode 100644
index 000000000..1d86f5e63
--- /dev/null
+++ b/vendor/github.com/prometheus/procfs/internal/util/sysreadfile_compat.go
@@ -0,0 +1,27 @@
+// 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.
+
+//go:build (linux && appengine) || (!linux && !darwin)
+// +build linux,appengine !linux,!darwin
+
+package util
+
+import (
+	"fmt"
+)
+
+// SysReadFile is here implemented as a noop for builds that do not support
+// the read syscall. For example Windows, or Linux on Google App Engine.
+func SysReadFile(file string) (string, error) {
+	return "", fmt.Errorf("not supported on this platform")
+}
diff --git a/vendor/github.com/prometheus/procfs/internal/util/valueparser.go b/vendor/github.com/prometheus/procfs/internal/util/valueparser.go
new file mode 100644
index 000000000..fe2355d3c
--- /dev/null
+++ b/vendor/github.com/prometheus/procfs/internal/util/valueparser.go
@@ -0,0 +1,91 @@
+// 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 util
+
+import (
+	"strconv"
+)
+
+// TODO(mdlayher): util packages are an anti-pattern and this should be moved
+// somewhere else that is more focused in the future.
+
+// A ValueParser enables parsing a single string into a variety of data types
+// in a concise and safe way. The Err method must be invoked after invoking
+// any other methods to ensure a value was successfully parsed.
+type ValueParser struct {
+	v   string
+	err error
+}
+
+// NewValueParser creates a ValueParser using the input string.
+func NewValueParser(v string) *ValueParser {
+	return &ValueParser{v: v}
+}
+
+// Int interprets the underlying value as an int and returns that value.
+func (vp *ValueParser) Int() int { return int(vp.int64()) }
+
+// PInt64 interprets the underlying value as an int64 and returns a pointer to
+// that value.
+func (vp *ValueParser) PInt64() *int64 {
+	if vp.err != nil {
+		return nil
+	}
+
+	v := vp.int64()
+	return &v
+}
+
+// int64 interprets the underlying value as an int64 and returns that value.
+// TODO: export if/when necessary.
+func (vp *ValueParser) int64() int64 {
+	if vp.err != nil {
+		return 0
+	}
+
+	// A base value of zero makes ParseInt infer the correct base using the
+	// string's prefix, if any.
+	const base = 0
+	v, err := strconv.ParseInt(vp.v, base, 64)
+	if err != nil {
+		vp.err = err
+		return 0
+	}
+
+	return v
+}
+
+// PUInt64 interprets the underlying value as an uint64 and returns a pointer to
+// that value.
+func (vp *ValueParser) PUInt64() *uint64 {
+	if vp.err != nil {
+		return nil
+	}
+
+	// A base value of zero makes ParseInt infer the correct base using the
+	// string's prefix, if any.
+	const base = 0
+	v, err := strconv.ParseUint(vp.v, base, 64)
+	if err != nil {
+		vp.err = err
+		return nil
+	}
+
+	return &v
+}
+
+// Err returns the last error, if any, encountered by the ValueParser.
+func (vp *ValueParser) Err() error {
+	return vp.err
+}