netdata/netdata

// SPDX-License-Identifier: GPL-3.0-or-later

package powerdns_recursor

import (
    "encoding/json"
    "errors"
    "fmt"
    "io"
    "net/http"
    "strconv"

    "github.com/netdata/netdata/go/go.d.plugin/pkg/web"
)

const (
    urlPathLocalStatistics = "/api/v1/servers/localhost/statistics"
)

func (r *Recursor) collect() (map[string]int64, error) {
    statistics, err := r.scrapeStatistics()
    if err != nil {
        return nil, err
    }

    collected := make(map[string]int64)

    r.collectStatistics(collected, statistics)

    if !isPowerDNSRecursorMetrics(collected) {
        return nil, errors.New("returned metrics aren't PowerDNS Recursor metrics")
    }

    return collected, nil
}

func isPowerDNSRecursorMetrics(collected map[string]int64) bool {
    // PowerDNS Authoritative Server has same endpoint and returns data in the same format.
    _, ok1 := collected["over-capacity-drops"]
    _, ok2 := collected["tcp-questions"]
    return ok1 && ok2
}

func (r *Recursor) collectStatistics(collected map[string]int64, statistics statisticMetrics) {
    for _, s := range statistics {
        // https://doc.powerdns.com/authoritative/http-api/statistics.html#statisticitem
        if s.Type != "StatisticItem" {
            continue
        }

        value, ok := s.Value.(string)
        if !ok {
            r.Debugf("%s value (%v) unexpected type: want=string, got=%T.", s.Name, s.Value, s.Value)
            continue
        }

        v, err := strconv.ParseInt(value, 10, 64)
        if err != nil {
            r.Debugf("%s value (%v) parse error: %v", s.Name, s.Value, err)
            continue
        }

        collected[s.Name] = v
    }
}

func (r *Recursor) scrapeStatistics() ([]statisticMetric, error) {
    req, _ := web.NewHTTPRequest(r.Request)
    req.URL.Path = urlPathLocalStatistics

    var statistics statisticMetrics
    if err := r.doOKDecode(req, &statistics); err != nil {
        return nil, err
    }

    return statistics, nil
}

func (r *Recursor) doOKDecode(req *http.Request, in interface{}) error {
    resp, err := r.httpClient.Do(req)
    if err != nil {
        return fmt.Errorf("error on HTTP request '%s': %v", req.URL, err)
    }
    defer closeBody(resp)

    if resp.StatusCode != http.StatusOK {
        return fmt.Errorf("'%s' returned HTTP status code: %d", req.URL, resp.StatusCode)
    }

    if err := json.NewDecoder(resp.Body).Decode(in); err != nil {
        return fmt.Errorf("error on decoding response from '%s': %v", req.URL, err)
    }
    return nil
}

func closeBody(resp *http.Response) {
    if resp != nil && resp.Body != nil {
        _, _ = io.Copy(io.Discard, resp.Body)
        _ = resp.Body.Close()
    }
}