From 4408aa0a1f3eadfd6c87a0a77df4659e690aadeb Mon Sep 17 00:00:00 2001
From: Dmitry Romanov <dmitry.romanov85@protonmail.com>
Date: Fri, 26 Apr 2024 14:59:03 +0700
Subject: [PATCH] metric for deleted and unclosed file descriptors

---
 fd/fds_collector.go | 52 +++++++++++++++++++++++++++++++++++++++++++++
 fd/file.d.go        |  1 +
 go.mod              |  2 +-
 3 files changed, 54 insertions(+), 1 deletion(-)
 create mode 100644 fd/fds_collector.go

diff --git a/fd/fds_collector.go b/fd/fds_collector.go
new file mode 100644
index 000000000..3f2485e6c
--- /dev/null
+++ b/fd/fds_collector.go
@@ -0,0 +1,52 @@
+package fd
+
+import (
+	"os"
+	"strings"
+
+	"github.com/ozontech/file.d/logger"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/procfs"
+)
+
+func newFdsCollector() prometheus.Collector {
+	c := &fdsCollector{
+		processDeletedFds: prometheus.NewDesc(
+			"process_deleted_fds",
+			"Number of deleted and unclosed file descriptors.",
+			nil, nil,
+		),
+	}
+	return c
+}
+
+type fdsCollector struct {
+	processDeletedFds *prometheus.Desc
+}
+
+func (f *fdsCollector) Collect(ch chan<- prometheus.Metric) {
+	p, err := procfs.NewProc(os.Getpid())
+	if err != nil {
+		logger.Errorf("failed to get procfs: %s", err.Error())
+		return
+	}
+
+	targets, err := p.FileDescriptorTargets()
+	if err != nil {
+		logger.Errorf("failed to read file descriptor targets: %s", err.Error())
+		return
+	}
+
+	processDeletedFds := 0
+	for _, target := range targets {
+		if strings.HasSuffix(target, " (deleted)") {
+			processDeletedFds++
+		}
+	}
+
+	ch <- prometheus.MustNewConstMetric(f.processDeletedFds, prometheus.GaugeValue, float64(processDeletedFds))
+}
+
+func (f *fdsCollector) Describe(ch chan<- *prometheus.Desc) {
+	ch <- f.processDeletedFds
+}
diff --git a/fd/file.d.go b/fd/file.d.go
index 65e21ce84..2b928b636 100644
--- a/fd/file.d.go
+++ b/fd/file.d.go
@@ -69,6 +69,7 @@ func (f *FileD) createRegistry() {
 	f.registry = prometheus.NewRegistry()
 	f.registry.MustRegister(prometheus.NewProcessCollector(prometheus.ProcessCollectorOpts{}))
 	f.registry.MustRegister(prometheus.NewGoCollector())
+	f.registry.MustRegister(newFdsCollector())
 }
 
 func (f *FileD) startPipelines() {
diff --git a/go.mod b/go.mod
index 1c64d9e88..dc8aa3dcc 100644
--- a/go.mod
+++ b/go.mod
@@ -27,6 +27,7 @@ require (
 	github.com/klauspost/compress v1.16.7
 	github.com/minio/minio-go v6.0.14+incompatible
 	github.com/prometheus/client_golang v1.16.0
+	github.com/prometheus/procfs v0.10.1
 	github.com/rjeczalik/notify v0.9.3
 	github.com/satori/go.uuid v1.2.0
 	github.com/stretchr/testify v1.8.4
@@ -120,7 +121,6 @@ require (
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/prometheus/client_model v0.3.0 // indirect
 	github.com/prometheus/common v0.42.0 // indirect
-	github.com/prometheus/procfs v0.10.1 // indirect
 	github.com/rcrowley/go-metrics v0.0.0-20201227073835-cf1acfcdf475 // indirect
 	github.com/ryanuber/go-glob v1.0.0 // indirect
 	github.com/segmentio/asm v1.2.0 // indirect