image/resources/knfsd-metrics-agent/internal/connections/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 connections

import (
	"bufio"
	"bytes"
	"context"
	"errors"
	"fmt"
	"os/exec"
	"time"

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

type scraper struct {
	mb *metadata.MetricsBuilder
}

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

func (s *scraper) scrape(ctx context.Context) (pdata.Metrics, error) {
	md := pdata.NewMetrics()
	now := pdata.NewTimestampFromTime(time.Now())

	// TODO: Consider counting unique clients (by IP) as well as total connections
	count, err := countConnectedClients(ctx)
	if err != nil {
		return md, err
	}

	metrics := md.ResourceMetrics().AppendEmpty().
		InstrumentationLibraryMetrics().AppendEmpty().
		Metrics()

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

func countConnectedClients(ctx context.Context) (int64, error) {
	var stdout, stderr bytes.Buffer
	cmd := exec.CommandContext(ctx, "ss",
		"--no-header", "--oneline", "--numeric",
		"--tcp", "--udp",
		"state", "established",
		"sport", "2049",
	)
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr
	err := cmd.Run()

	if err != nil {
		var exit *exec.ExitError
		if errors.As(err, &exit) {
			err = fmt.Errorf("command terminated with exit code %d\n%s", exit.ExitCode(), stderr.String())
		}
		return 0, err
	}

	var count int64
	s := bufio.NewScanner(&stdout)
	for s.Scan() {
		count++
	}

	err = s.Err()
	if err != nil {
		return 0, err
	}

	return count, nil
}