bcachefs collector (#3523)

Add support for collecting and reporting metrics from bcachefs
filesystems.

Signed-off-by: Ananth Bhaskararaman <antsub@gmail.com>

Author: ananthb

collector/bcachefs_linux.go

@@ -0,0 +1,275 @@
+// Copyright 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 !nobcachefs
+
+package collector
+
+import (
+	"fmt"
+	"log/slog"
+	"os"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/procfs/bcachefs"
+)
+
+const subsystem = "bcachefs"
+
+var (
+	bcachefsInfoDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, subsystem, "info"),
+		"Filesystem information.",
+		[]string{"uuid"},
+		nil,
+	)
+	bcachefsBtreeCacheSizeBytes = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, subsystem, "btree_cache_size_bytes"),
+		"Btree cache memory usage in bytes.",
+		[]string{"uuid"},
+		nil,
+	)
+	bcachefsCompressionCompressedBytesDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, subsystem, "compression_compressed_bytes"),
+		"Compressed size by algorithm.",
+		[]string{"uuid", "algorithm"},
+		nil,
+	)
+	bcachefsCompressionUncompressedBytesDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, subsystem, "compression_uncompressed_bytes"),
+		"Uncompressed size by algorithm.",
+		[]string{"uuid", "algorithm"},
+		nil,
+	)
+	bcachefsErrorsTotalDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, subsystem, "errors_total"),
+		"Error count by error type.",
+		[]string{"uuid", "error_type"},
+		nil,
+	)
+	bcachefsBtreeWritesTotalDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, subsystem, "btree_writes_total"),
+		"Number of btree writes by type.",
+		[]string{"uuid", "type"},
+		nil,
+	)
+	bcachefsBtreeWriteAverageSizeBytesDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, subsystem, "btree_write_average_size_bytes"),
+		"Average btree write size by type.",
+		[]string{"uuid", "type"},
+		nil,
+	)
+	bcachefsDeviceInfoDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, subsystem, "device_info"),
+		"Device information.",
+		[]string{"uuid", "device", "label", "state"},
+		nil,
+	)
+	bcachefsDeviceBucketSizeBytesDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, subsystem, "device_bucket_size_bytes"),
+		"Bucket size in bytes.",
+		[]string{"uuid", "device"},
+		nil,
+	)
+	bcachefsDeviceBucketsDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, subsystem, "device_buckets"),
+		"Total number of buckets.",
+		[]string{"uuid", "device"},
+		nil,
+	)
+	bcachefsDeviceDurabilityDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, subsystem, "device_durability"),
+		"Device durability setting.",
+		[]string{"uuid", "device"},
+		nil,
+	)
+	bcachefsDeviceIODoneBytesTotalDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, subsystem, "device_io_done_bytes_total"),
+		"IO bytes by operation type and data type.",
+		[]string{"uuid", "device", "operation", "data_type"},
+		nil,
+	)
+	bcachefsDeviceIOErrorsTotalDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, subsystem, "device_io_errors_total"),
+		"IO errors by error type.",
+		[]string{"uuid", "device", "type"},
+		nil,
+	)
+)
+
+func init() {
+	registerCollector(subsystem, defaultEnabled, NewBcachefsCollector)
+}
+
+// bcachefsCollector collects metrics from bcachefs filesystems.
+type bcachefsCollector struct {
+	fs     bcachefs.FS
+	logger *slog.Logger
+}
+
+// NewBcachefsCollector returns a new Collector exposing bcachefs statistics.
+func NewBcachefsCollector(logger *slog.Logger) (Collector, error) {
+	fs, err := bcachefs.NewFS(*sysPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open sysfs: %w", err)
+	}
+
+	return &bcachefsCollector{
+		fs:     fs,
+		logger: logger,
+	}, nil
+}
+
+// Update retrieves and exports bcachefs statistics.
+func (c *bcachefsCollector) Update(ch chan<- prometheus.Metric) error {
+	stats, err := c.fs.Stats()
+	if err != nil {
+		if os.IsNotExist(err) {
+			c.logger.Debug("bcachefs sysfs path does not exist", "path", sysFilePath("fs/bcachefs"))
+			return ErrNoData
+		}
+		return fmt.Errorf("failed to retrieve bcachefs stats: %w", err)
+	}
+
+	if len(stats) == 0 {
+		return ErrNoData
+	}
+
+	for _, s := range stats {
+		uuid := s.UUID
+
+		ch <- prometheus.MustNewConstMetric(
+			bcachefsInfoDesc,
+			prometheus.GaugeValue,
+			1,
+			uuid,
+		)
+
+		ch <- prometheus.MustNewConstMetric(
+			bcachefsBtreeCacheSizeBytes,
+			prometheus.GaugeValue,
+			float64(s.BtreeCacheSizeBytes),
+			uuid,
+		)
+
+		for algorithm, comp := range s.Compression {
+			ch <- prometheus.MustNewConstMetric(
+				bcachefsCompressionCompressedBytesDesc,
+				prometheus.GaugeValue,
+				float64(comp.CompressedBytes),
+				uuid, algorithm,
+			)
+			ch <- prometheus.MustNewConstMetric(
+				bcachefsCompressionUncompressedBytesDesc,
+				prometheus.GaugeValue,
+				float64(comp.UncompressedBytes),
+				uuid, algorithm,
+			)
+		}
+
+		for errorType, errStats := range s.Errors {
+			ch <- prometheus.MustNewConstMetric(
+				bcachefsErrorsTotalDesc,
+				prometheus.CounterValue,
+				float64(errStats.Count),
+				uuid, errorType,
+			)
+		}
+
+		for counterName, counterStats := range s.Counters {
+			metricName := SanitizeMetricName(counterName) + "_total"
+			ch <- prometheus.MustNewConstMetric(
+				prometheus.NewDesc(
+					prometheus.BuildFQName(namespace, subsystem, metricName),
+					fmt.Sprintf("Bcachefs counter %s since filesystem creation.", counterName),
+					[]string{"uuid"},
+					nil,
+				),
+				prometheus.CounterValue,
+				float64(counterStats.SinceFilesystemCreation),
+				uuid,
+			)
+		}
+
+		for writeType, writeStats := range s.BtreeWrites {
+			ch <- prometheus.MustNewConstMetric(
+				bcachefsBtreeWritesTotalDesc,
+				prometheus.CounterValue,
+				float64(writeStats.Count),
+				uuid, writeType,
+			)
+			ch <- prometheus.MustNewConstMetric(
+				bcachefsBtreeWriteAverageSizeBytesDesc,
+				prometheus.GaugeValue,
+				float64(writeStats.SizeBytes),
+				uuid, writeType,
+			)
+		}
+
+		for device, devStats := range s.Devices {
+			if devStats == nil {
+				continue
+			}
+
+			ch <- prometheus.MustNewConstMetric(
+				bcachefsDeviceInfoDesc,
+				prometheus.GaugeValue,
+				1,
+				uuid, device, devStats.Label, devStats.State,
+			)
+
+			ch <- prometheus.MustNewConstMetric(
+				bcachefsDeviceBucketSizeBytesDesc,
+				prometheus.GaugeValue,
+				float64(devStats.BucketSizeBytes),
+				uuid, device,
+			)
+
+			ch <- prometheus.MustNewConstMetric(
+				bcachefsDeviceBucketsDesc,
+				prometheus.GaugeValue,
+				float64(devStats.Buckets),
+				uuid, device,
+			)
+
+			ch <- prometheus.MustNewConstMetric(
+				bcachefsDeviceDurabilityDesc,
+				prometheus.GaugeValue,
+				float64(devStats.Durability),
+				uuid, device,
+			)
+
+			for op, dataTypes := range devStats.IODone {
+				for dataType, value := range dataTypes {
+					ch <- prometheus.MustNewConstMetric(
+						bcachefsDeviceIODoneBytesTotalDesc,
+						prometheus.CounterValue,
+						float64(value),
+						uuid, device, op, dataType,
+					)
+				}
+			}
+
+			for errorType, value := range devStats.IOErrors {
+				ch <- prometheus.MustNewConstMetric(
+					bcachefsDeviceIOErrorsTotalDesc,
+					prometheus.CounterValue,
+					float64(value),
+					uuid, device, errorType,
+				)
+			}
+		}
+	}
+
+	return nil
+}