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ddevault committed Sep 18, 2020
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19 changes: 19 additions & 0 deletions LICENSE
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Copyright (c) 2020 Drew DeVault

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
33 changes: 33 additions & 0 deletions README.md
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# chartsrv

chartsrv is a dead-simple web application which runs [Prometheus][0] queries and
charts the result as an SVG.

[0]: https://prometheus.io/

## Running the daemon

```
$ go build -o chartsrv main.go
$ ./chartsrv https://prometheus.example.org
Listening on :8142
```

Forward `/chart.svg` to this address with your favorite reverse proxy.

## Usage

Create a URL like `https://chartsrv.example.org/chart.svg?query=...&args...` and
set the query parameters as appropriate:

- **query**: required. Prometheus query to execute.
- **title**: chart title
- **stacked**: set to create an area chart instead of a line chart
- **since**: [time.ParseDuration][1] to set distance in the past to start
charting from
- **width**: chart width in inches
- **height**: chart height in inches
- **step**: number of seconds between data points
- **max**: maximum Y value

[1]: https://golang.org/pkg/time/#ParseDuration
8 changes: 8 additions & 0 deletions go.mod
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module git.sr.ht/~sircmpwn/promsvg

go 1.15

require (
github.com/go-chi/chi v4.1.2+incompatible // indirect
gonum.org/v1/plot v0.8.0 // indirect
)
63 changes: 63 additions & 0 deletions go.sum
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dmitri.shuralyov.com/gpu/mtl v0.0.0-20190408044501-666a987793e9/go.mod h1:H6x//7gZCb22OMCxBHrMx7a5I7Hp++hsVxbQ4BYO7hU=
gioui.org v0.0.0-20200628203458-851255f7a67b/go.mod h1:jiUwifN9cRl/zmco43aAqh0aV+s9GbhG13KcD+gEpkU=
github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
github.com/ajstarks/svgo v0.0.0-20180226025133-644b8db467af h1:wVe6/Ea46ZMeNkQjjBW6xcqyQA/j5e0D6GytH95g0gQ=
github.com/ajstarks/svgo v0.0.0-20180226025133-644b8db467af/go.mod h1:K08gAheRH3/J6wwsYMMT4xOr94bZjxIelGM0+d/wbFw=
github.com/boombuler/barcode v1.0.0/go.mod h1:paBWMcWSl3LHKBqUq+rly7CNSldXjb2rDl3JlRe0mD8=
github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/fogleman/gg v1.2.1-0.20190220221249-0403632d5b90/go.mod h1:R/bRT+9gY/C5z7JzPU0zXsXHKM4/ayA+zqcVNZzPa1k=
github.com/fogleman/gg v1.3.0 h1:/7zJX8F6AaYQc57WQCyN9cAIz+4bCJGO9B+dyW29am8=
github.com/fogleman/gg v1.3.0/go.mod h1:R/bRT+9gY/C5z7JzPU0zXsXHKM4/ayA+zqcVNZzPa1k=
github.com/go-chi/chi v1.0.0 h1:s/kv1cTXfivYjdKJdyUzNGyAWZ/2t7duW1gKn5ivu+c=
github.com/go-chi/chi v4.1.2+incompatible h1:fGFk2Gmi/YKXk0OmGfBh0WgmN3XB8lVnEyNz34tQRec=
github.com/go-chi/chi v4.1.2+incompatible/go.mod h1:eB3wogJHnLi3x/kFX2A+IbTBlXxmMeXJVKy9tTv1XzQ=
github.com/go-fonts/dejavu v0.1.0/go.mod h1:4Wt4I4OU2Nq9asgDCteaAaWZOV24E+0/Pwo0gppep4g=
github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1/go.mod h1:vR7hzQXu2zJy9AVAgeJqvqgH9Q5CA+iKCZ2gyEVpxRU=
github.com/go-latex/latex v0.0.0-20200518072620-0806b477ea35 h1:uroDDLmuCK5Pz5J/Ef5vCL6F0sJmAtZFTm0/cF027F4=
github.com/go-latex/latex v0.0.0-20200518072620-0806b477ea35/go.mod h1:PNI+CcWytn/2Z/9f1SGOOYn0eILruVyp0v2/iAs8asQ=
github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 h1:DACJavvAHhabrF08vX0COfcOBJRhZ8lUbR+ZWIs0Y5g=
github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0/go.mod h1:E/TSTwGwJL78qG/PmXZO1EjYhfJinVAhrmmHX6Z8B9k=
github.com/jung-kurt/gofpdf v1.0.0/go.mod h1:7Id9E/uU8ce6rXgefFLlgrJj/GYY22cpxn+r32jIOes=
github.com/jung-kurt/gofpdf v1.0.3-0.20190309125859-24315acbbda5/go.mod h1:7Id9E/uU8ce6rXgefFLlgrJj/GYY22cpxn+r32jIOes=
github.com/jung-kurt/gofpdf v1.16.2 h1:jgbatWHfRlPYiK85qgevsZTHviWXKwB1TTiKdz5PtRc=
github.com/jung-kurt/gofpdf v1.16.2/go.mod h1:1hl7y57EsiPAkLbOwzpzqgx1A30nQCk/YmFV8S2vmK0=
github.com/phpdave11/gofpdi v1.0.7/go.mod h1:vBmVV0Do6hSBHC8uKUQ71JGW+ZGQq74llk/7bXwjDoI=
github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/ruudk/golang-pdf417 v0.0.0-20181029194003-1af4ab5afa58/go.mod h1:6lfFZQK844Gfx8o5WFuvpxWRwnSoipWe/p622j1v06w=
github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
golang.org/x/exp v0.0.0-20180321215751-8460e604b9de/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
golang.org/x/exp v0.0.0-20180807140117-3d87b88a115f/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
golang.org/x/exp v0.0.0-20190125153040-c74c464bbbf2/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
golang.org/x/exp v0.0.0-20190306152737-a1d7652674e8/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
golang.org/x/exp v0.0.0-20191002040644-a1355ae1e2c3/go.mod h1:NOZ3BPKG0ec/BKJQgnvsSFpcKLM5xXVWnvZS97DWHgE=
golang.org/x/image v0.0.0-20180708004352-c73c2afc3b81/go.mod h1:ux5Hcp/YLpHSI86hEcLt0YII63i6oz57MZXIpbrjZUs=
golang.org/x/image v0.0.0-20190227222117-0694c2d4d067/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
golang.org/x/image v0.0.0-20190802002840-cff245a6509b/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
golang.org/x/image v0.0.0-20190910094157-69e4b8554b2a/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
golang.org/x/image v0.0.0-20200430140353-33d19683fad8/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
golang.org/x/image v0.0.0-20200618115811-c13761719519 h1:1e2ufUJNM3lCHEY5jIgac/7UTjd6cgJNdatjPdFWf34=
golang.org/x/image v0.0.0-20200618115811-c13761719519/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
golang.org/x/mobile v0.0.0-20190719004257-d2bd2a29d028/go.mod h1:E/iHnbuqvinMTCcRqshq8CkpyQDoeVncDDYHnLhea+o=
golang.org/x/mod v0.1.0/go.mod h1:0QHyrYULN0/3qlju5TqG8bIK38QM8yzMo5ekMj3DlcY=
golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
golang.org/x/sys v0.0.0-20190312061237-fead79001313/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20200124204421-9fbb57f87de9/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
golang.org/x/tools v0.0.0-20180525024113-a5b4c53f6e8b/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
golang.org/x/tools v0.0.0-20190206041539-40960b6deb8e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
golang.org/x/tools v0.0.0-20190927191325-030b2cf1153e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
gonum.org/v1/gonum v0.0.0-20180816165407-929014505bf4/go.mod h1:Y+Yx5eoAFn32cQvJDxZx5Dpnq+c3wtXuadVZAcxbbBo=
gonum.org/v1/gonum v0.8.1/go.mod h1:oe/vMfY3deqTw+1EZJhuvEW2iwGF1bW9wwu7XCu0+v0=
gonum.org/v1/netlib v0.0.0-20190313105609-8cb42192e0e0/go.mod h1:wa6Ws7BG/ESfp6dHfk7C6KdzKA7wR7u/rKwOGE66zvw=
gonum.org/v1/plot v0.0.0-20190515093506-e2840ee46a6b/go.mod h1:Wt8AAjI+ypCyYX3nZBvf6cAIx93T+c/OS2HFAYskSZc=
gonum.org/v1/plot v0.8.0 h1:dNgubmltsMoehfn6XgbutHpicbUfbkcGSxkICy1bC4o=
gonum.org/v1/plot v0.8.0/go.mod h1:3GH8dTfoceRTELDnv+4HNwbvM/eMfdDUGHFG2bo3NeE=
rsc.io/pdf v0.1.1/go.mod h1:n8OzWcQ6Sp37PL01nO98y4iUCRdTGarVfzxY20ICaU4=
272 changes: 272 additions & 0 deletions main.go
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package main

import (
"encoding/json"
"fmt"
"image/color"
"log"
"net/http"
"net/url"
"os"
"sort"
"strconv"
"strings"
"time"

"github.com/go-chi/chi"
"github.com/go-chi/chi/middleware"
"gonum.org/v1/plot"
"gonum.org/v1/plot/plotter"
"gonum.org/v1/plot/plotutil"
"gonum.org/v1/plot/vg"
)

var (
upstream string
)

type PromResponse struct {
Status string `json:"status"`
Data struct {
ResultType string `json:"resultType"`
Result []struct {
Metric map[string]string `json:"metric"`
Values [][]interface{} `json:"values"`
} `json:"result"`
} `json:"data"`
}

type Datapoint struct {
Time time.Time
Value float64
}

type PromResult struct {
Metric string
Values []Datapoint
}

func Query(q string, start time.Time, end time.Time, step int) ([]PromResult, error) {
body := url.Values{}
body.Set("query", q)
body.Set("start", fmt.Sprintf("%d", start.Unix()))
body.Set("end", fmt.Sprintf("%d", end.Unix()))
body.Set("step", fmt.Sprintf("%d", step))
resp, err := http.Post(fmt.Sprintf("%s/api/v1/query_range", upstream),
"application/x-www-form-urlencoded", strings.NewReader(body.Encode()))
if err != nil {
return nil, err
}
defer resp.Body.Close()

if resp.StatusCode != 200 {
return nil, fmt.Errorf("Received %d response from upstream", resp.StatusCode)
}

var data PromResponse
if err := json.NewDecoder(resp.Body).Decode(&data); err != nil {
return nil, err
}

if data.Data.ResultType != "matrix" {
return nil, fmt.Errorf("result type isn't of type matrix: %s",
data.Data.ResultType)
}

if len(data.Data.Result) == 0 {
return nil, fmt.Errorf("No data")
}

var results []PromResult
for _, res := range data.Data.Result {
r := PromResult{}
r.Metric = metricName(res.Metric)

var values []Datapoint
for _, vals := range res.Values {
timestamp := vals[0].(float64)
value := vals[1].(string)
fv, _ := strconv.ParseFloat(value, 64)
values = append(values, Datapoint{
time.Unix(int64(timestamp), 0),
fv,
})
}
r.Values = values

results = append(results, r)
}
return results, nil
}

func metricName(metric map[string]string) string {
if len(metric) == 0 {
return "{}"
}

out := ""
var inner []string
for key, value := range metric {
if key == "__name__" {
out = value
continue
}
inner = append(inner, fmt.Sprintf(`%s="%s"`, key, value))
}

if len(inner) == 0 {
return out
}

sort.Slice(inner, func(i, j int) bool {
return inner[i] < inner[j]
})

return out + "{" + strings.Join(inner, ",") + "}"
}

func main() {
plotutil.DefaultDashes = [][]vg.Length{{}}

upstream = os.Args[1]
router := chi.NewRouter()
router.Use(middleware.RealIP)
router.Use(middleware.Logger)

router.Get("/chart.svg", func(w http.ResponseWriter, r *http.Request) {
args := r.URL.Query()
var query string
if q, ok := args["query"]; !ok {
w.WriteHeader(400)
w.Write([]byte("Expected ?query=... parameter"))
return
} else {
query = q[0]
}

start := time.Now().Add(-24 * 60 * time.Minute)
end := time.Now()
if s, ok := args["since"]; ok {
d, _ := time.ParseDuration(s[0])
start = time.Now().Add(-d)
}

width := 12*vg.Inch
height := 6*vg.Inch
if ws, ok := args["width"]; ok {
w, _ := strconv.ParseFloat(ws[0], 32)
width = vg.Length(w)*vg.Inch
}
if hs, ok := args["height"]; ok {
h, _ := strconv.ParseFloat(hs[0], 32)
height = vg.Length(h)*vg.Inch
}

// Set step so that there's approximately 25 data points per inch
step := int(end.Sub(start).Seconds() / (25 * float64(width / vg.Inch)))
if s, ok := args["step"]; ok {
d, _ := strconv.ParseInt(s[0], 10, 32)
step = int(d)
}
_, stacked := args["stacked"]

data, err := Query(query, start, end, step)
if err != nil {
w.WriteHeader(400)
w.Write([]byte(fmt.Sprintf("%v", err)))
return
}

p, err := plot.New()
if err != nil {
panic(err)
}
if t, ok := args["title"]; ok {
p.Title.Text = t[0]
}
p.X.Label.Text = "Time"
p.X.Tick.Marker = dateTicks{}
if ms, ok := args["max"]; ok {
m, _ := strconv.ParseFloat(ms[0], 64)
p.Y.Max = m
}
p.Legend.Top = true

sums := make([]float64, len(data[0].Values))

plotters := make([]plot.Plotter, len(data))
var nextColor int
colors := plotutil.SoftColors
for i, res := range data {
var points plotter.XYs
for j, d := range res.Values {
value := d.Value
if stacked {
value += sums[j]
}
points = append(points, plotter.XY{
float64(d.Time.Unix()),
value,
})
sums[j] += d.Value
}

l, _, err := plotter.NewLinePoints(points)
if err != nil {
w.WriteHeader(400)
w.Write([]byte(fmt.Sprintf("%v", err)))
return
}
if stacked {
l.FillColor = colors[nextColor]
if i != len(data) - 1 {
l.Color = color.RGBA{0, 0, 0, 0}
}
} else {
l.Color = colors[nextColor]
}
nextColor += 1
if nextColor >= len(colors) {
nextColor = 0
}
plotters[i] = l
p.Legend.Add(res.Metric, l)
}
for i := len(plotters) - 1; i >= 0; i-- {
p.Add(plotters[i])
}

writer, err := p.WriterTo(width, height, "svg")
if err != nil {
w.WriteHeader(400)
w.Write([]byte(fmt.Sprintf("%v", err)))
return
}

w.Header().Add("Content-Type", "image/svg+xml")
writer.WriteTo(w)
})

addr := ":8142"
if len(os.Args) > 2 {
addr = os.Args[2]
}
log.Printf("Listening on %s", addr)
http.ListenAndServe(addr, router)
}

type dateTicks struct{}
// Ticks computes the default tick marks, but inserts commas
// into the labels for the major tick marks.
func (dateTicks) Ticks(min, max float64) []plot.Tick {
tks := plot.DefaultTicks{}.Ticks(min, max)
for i, t := range tks {
if t.Label == "" { // Skip minor ticks, they are fine.
continue
}
d, _ := strconv.ParseFloat(t.Label, 64)
tm := time.Unix(int64(d), 0)
tks[i].Label = tm.Format("15:04:05")
}
return tks
}

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