[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, 102 insertions, 0 deletions

diff --git a/vendor/github.com/prometheus/procfs/proc_psi.go b/vendor/github.com/prometheus/procfs/proc_psi.go
new file mode 100644
index 000000000..fe9dbb425
--- /dev/null
+++ b/vendor/github.com/prometheus/procfs/proc_psi.go
@@ -0,0 +1,102 @@
+// 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
+
+// The PSI / pressure interface is described at
+//   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/accounting/psi.txt
+// Each resource (cpu, io, memory, ...) is exposed as a single file.
+// Each file may contain up to two lines, one for "some" pressure and one for "full" pressure.
+// Each line contains several averages (over n seconds) and a total in µs.
+//
+// Example io pressure file:
+// > some avg10=0.06 avg60=0.21 avg300=0.99 total=8537362
+// > full avg10=0.00 avg60=0.13 avg300=0.96 total=8183134
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/prometheus/procfs/internal/util"
+)
+
+const lineFormat = "avg10=%f avg60=%f avg300=%f total=%d"
+
+// PSILine is a single line of values as returned by `/proc/pressure/*`.
+//
+// The Avg entries are averages over n seconds, as a percentage.
+// The Total line is in microseconds.
+type PSILine struct {
+	Avg10  float64
+	Avg60  float64
+	Avg300 float64
+	Total  uint64
+}
+
+// PSIStats represent pressure stall information from /proc/pressure/*
+//
+// "Some" indicates the share of time in which at least some tasks are stalled.
+// "Full" indicates the share of time in which all non-idle tasks are stalled simultaneously.
+type PSIStats struct {
+	Some *PSILine
+	Full *PSILine
+}
+
+// PSIStatsForResource reads pressure stall information for the specified
+// resource from /proc/pressure/<resource>. At time of writing this can be
+// either "cpu", "memory" or "io".
+func (fs FS) PSIStatsForResource(resource string) (PSIStats, error) {
+	data, err := util.ReadFileNoStat(fs.proc.Path(fmt.Sprintf("%s/%s", "pressure", resource)))
+	if err != nil {
+		return PSIStats{}, fmt.Errorf("%s: psi_stats: unavailable for %q: %w", ErrFileRead, resource, err)
+	}
+
+	return parsePSIStats(bytes.NewReader(data))
+}
+
+// parsePSIStats parses the specified file for pressure stall information.
+func parsePSIStats(r io.Reader) (PSIStats, error) {
+	psiStats := PSIStats{}
+
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		l := scanner.Text()
+		prefix := strings.Split(l, " ")[0]
+		switch prefix {
+		case "some":
+			psi := PSILine{}
+			_, err := fmt.Sscanf(l, fmt.Sprintf("some %s", lineFormat), &psi.Avg10, &psi.Avg60, &psi.Avg300, &psi.Total)
+			if err != nil {
+				return PSIStats{}, err
+			}
+			psiStats.Some = &psi
+		case "full":
+			psi := PSILine{}
+			_, err := fmt.Sscanf(l, fmt.Sprintf("full %s", lineFormat), &psi.Avg10, &psi.Avg60, &psi.Avg300, &psi.Total)
+			if err != nil {
+				return PSIStats{}, err
+			}
+			psiStats.Full = &psi
+		default:
+			// If we encounter a line with an unknown prefix, ignore it and move on
+			// Should new measurement types be added in the future we'll simply ignore them instead
+			// of erroring on retrieval
+			continue
+		}
+	}
+
+	return psiStats, nil
+}