image/resources/knfsd-metrics-agent/internal/slab/scraper.go

/*
 Copyright 2022 Google LLC

 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

      https://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 slab

import (
	"context"
	"time"

	"github.com/GoogleCloudPlatform/knfsd-cache-utils/image/resources/knfsd-metrics-agent/internal/slab/internal/metadata"
	"github.com/prometheus/procfs"
	"go.opentelemetry.io/collector/component"
	"go.opentelemetry.io/collector/model/pdata"
	"go.opentelemetry.io/collector/receiver/scraperhelper"
)

type slabScraper struct {
	fs procfs.FS
	mb *metadata.MetricsBuilder
}

func newScraper(cfg *Config) (scraperhelper.Scraper, error) {
	s := &slabScraper{
		mb: metadata.NewMetricsBuilder(cfg.Metrics),
	}
	return scraperhelper.NewScraper(
		typeStr,
		s.scrape,
		scraperhelper.WithStart(s.start))
}

func (s *slabScraper) start(context.Context, component.Host) error {
	fs, err := procfs.NewDefaultFS()
	if err != nil {
		return err
	}

	// Verify we can scrape slabinfo, most common reason this will fail is
	// because of permissions (needs to be root).
	_, err = fs.SlabInfo()
	// TODO: check for transient errors?
	if err != nil {
		return err
	}

	s.fs = fs
	return nil
}

func (s *slabScraper) scrape(ctx context.Context) (pdata.Metrics, error) {
	md := pdata.NewMetrics()

	info, err := s.fs.SlabInfo()
	if err != nil {
		return md, err
	}

	now := pdata.NewTimestampFromTime(time.Now())
	metrics := md.ResourceMetrics().AppendEmpty().
		InstrumentationLibraryMetrics().AppendEmpty().
		Metrics()

	dentry := find(info.Slabs, "dentry")
	if dentry != nil {
		s.mb.RecordSlabDentryCacheActiveObjectsDataPoint(now, dentry.ObjActive)
		s.mb.RecordSlabDentryCacheObjsizeDataPoint(now, dentry.ObjSize)
	}

	nfs := find(info.Slabs, "nfs_inode_cache")
	if nfs != nil {
		s.mb.RecordSlabNfsInodeCacheActiveObjectsDataPoint(now, nfs.ObjActive)
		s.mb.RecordSlabNfsInodeCacheObjsizeDataPoint(now, nfs.ObjSize)
	}

	s.mb.Emit(metrics)
	return md, nil
}

func find(slabs []*procfs.Slab, name string) *procfs.Slab {
	for _, s := range slabs {
		if s.Name == name {
			return s
		}
	}
	return nil
}