| // Copyright 2022 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. |
| |
| // PROOF OF CONCEPT ONLY |
| // |
| // This is an experiment in providing a nicer experience for the "look at the |
| // metrics page in a browser" experience. It provides a path forward should we |
| // ever want to make a binary format the default for actual scraping. When |
| // negotiating a format with the client, we can take into account that the |
| // client may be a browser, and is asking for text/html. |
| |
| package expfmt |
| |
| import ( |
| "bytes" |
| "html/template" |
| "io" |
| |
| dto "github.com/prometheus/client_model/go" |
| ) |
| |
| // TODO: make this prettier |
| var preamble = []byte("<html><head><title>Metrics</title></head><body><h1>Metrics</h1>") |
| var metricFamilyTemplate = template.Must(template.New("metrics-page").Parse(`<pre>{{.}}</pre>`)) |
| var postamble = []byte("</body></html>") |
| |
| // MetricFamilyToHTML writes the HTML for a single MetricFamily. |
| func MetricFamilyToHTML(out io.Writer, in *dto.MetricFamily) error { |
| buf := &bytes.Buffer{} |
| |
| _, err := MetricFamilyToText(buf, in) |
| if err != nil { |
| return nil |
| } |
| |
| return metricFamilyTemplate.Execute(out, buf) |
| } |
| |
| // HTMLPreamble writes the header and general front matter for the HTML |
| // representation. |
| func HTMLPreamble(out io.Writer) error { |
| _, err := out.Write(preamble) |
| return err |
| } |
| |
| // HTMLPostamble writes the footer and closing tags for the HTML representation. |
| // It closes all tags opened in the preamble. |
| func HTMLPostamble(out io.Writer) error { |
| _, err := out.Write(postamble) |
| return err |
| } |
| |
| func NewHTMLEncoder(w io.Writer) encoderCloser { |
| // TODO: don't swallow errors. The current interfaces don't allow for a global preamble, so we're writing it right here 🤞 |
| _ = HTMLPreamble(w) |
| return encoderCloser{ |
| encode: func(v *dto.MetricFamily) error { |
| return MetricFamilyToHTML(w, v) |
| }, |
| close: func() error { return HTMLPostamble(w) }, |
| } |
| } |
