1 files changed, 155 insertions, 0 deletions
diff --git a/src/go/collectors/go.d.plugin/pkg/prometheus/client.go b/src/go/collectors/go.d.plugin/pkg/prometheus/client.go
new file mode 100644
index 000000000..3365b270c
--- /dev/null
+++ b/src/go/collectors/go.d.plugin/pkg/prometheus/client.go
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package prometheus
+
+import (
+	"bufio"
+	"bytes"
+	"compress/gzip"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"path/filepath"
+
+	"github.com/netdata/netdata/go/go.d.plugin/pkg/prometheus/selector"
+	"github.com/netdata/netdata/go/go.d.plugin/pkg/web"
+)
+
+type (
+	// Prometheus is a helper for scrape and parse prometheus format metrics.
+	Prometheus interface {
+		// ScrapeSeries and parse prometheus format metrics
+		ScrapeSeries() (Series, error)
+		Scrape() (MetricFamilies, error)
+		HTTPClient() *http.Client
+	}
+
+	prometheus struct {
+		client   *http.Client
+		request  web.Request
+		filepath string
+
+		sr selector.Selector
+
+		parser promTextParser
+
+		buf     *bytes.Buffer
+		gzipr   *gzip.Reader
+		bodyBuf *bufio.Reader
+	}
+)
+
+const (
+	acceptHeader = `text/plain;version=0.0.4;q=1,*/*;q=0.1`
+)
+
+// New creates a Prometheus instance.
+func New(client *http.Client, request web.Request) Prometheus {
+	return &prometheus{
+		client:  client,
+		request: request,
+		buf:     bytes.NewBuffer(make([]byte, 0, 16000)),
+	}
+}
+
+// NewWithSelector creates a Prometheus instance with the selector.
+func NewWithSelector(client *http.Client, request web.Request, sr selector.Selector) Prometheus {
+	p := &prometheus{
+		client:  client,
+		request: request,
+		sr:      sr,
+		buf:     bytes.NewBuffer(make([]byte, 0, 16000)),
+		parser:  promTextParser{sr: sr},
+	}
+
+	if v, err := url.Parse(request.URL); err == nil && v.Scheme == "file" {
+		p.filepath = filepath.Join(v.Host, v.Path)
+	}
+
+	return p
+}
+
+func (p *prometheus) HTTPClient() *http.Client {
+	return p.client
+}
+
+// ScrapeSeries scrapes metrics, parses and sorts
+func (p *prometheus) ScrapeSeries() (Series, error) {
+	p.buf.Reset()
+
+	if err := p.fetch(p.buf); err != nil {
+		return nil, err
+	}
+
+	return p.parser.parseToSeries(p.buf.Bytes())
+}
+
+func (p *prometheus) Scrape() (MetricFamilies, error) {
+	p.buf.Reset()
+
+	if err := p.fetch(p.buf); err != nil {
+		return nil, err
+	}
+
+	return p.parser.parseToMetricFamilies(p.buf.Bytes())
+}
+
+func (p *prometheus) fetch(w io.Writer) error {
+	// TODO: should be a separate text file prom client
+	if p.filepath != "" {
+		f, err := os.Open(p.filepath)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+
+		_, err = io.Copy(w, f)
+
+		return err
+	}
+
+	req, err := web.NewHTTPRequest(p.request)
+	if err != nil {
+		return err
+	}
+
+	req.Header.Add("Accept", acceptHeader)
+	req.Header.Add("Accept-Encoding", "gzip")
+
+	resp, err := p.client.Do(req)
+	if err != nil {
+		return err
+	}
+
+	defer func() {
+		_, _ = io.Copy(io.Discard, resp.Body)
+		_ = resp.Body.Close()
+	}()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("server '%s' returned HTTP status code %d (%s)", req.URL, resp.StatusCode, resp.Status)
+	}
+
+	if resp.Header.Get("Content-Encoding") != "gzip" {
+		_, err = io.Copy(w, resp.Body)
+		return err
+	}
+
+	if p.gzipr == nil {
+		p.bodyBuf = bufio.NewReader(resp.Body)
+		p.gzipr, err = gzip.NewReader(p.bodyBuf)
+		if err != nil {
+			return err
+		}
+	} else {
+		p.bodyBuf.Reset(resp.Body)
+		_ = p.gzipr.Reset(p.bodyBuf)
+	}
+
+	_, err = io.Copy(w, p.gzipr)
+	_ = p.gzipr.Close()
+
+	return err
+}