From b5e9076c6e1683e4d2384ac76e85ad1503c5336a Mon Sep 17 00:00:00 2001 From: Martin Fischer Date: Sat, 17 Jan 2026 20:07:17 +0100 Subject: initial commit --- .gitignore | 1 + LICENSE | 19 ++++++++ README.md | 19 ++++++++ default.nix | 8 ++++ go.mod | 31 +++++++++++++ go.sum | 83 ++++++++++++++++++++++++++++++++++ hashes.nix | 3 ++ main.go | 144 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ main_test.go | 90 +++++++++++++++++++++++++++++++++++++ service.nix | 35 +++++++++++++++ 10 files changed, 433 insertions(+) create mode 100644 .gitignore create mode 100644 LICENSE create mode 100644 README.md create mode 100644 default.nix create mode 100644 go.mod create mode 100644 go.sum create mode 100644 hashes.nix create mode 100644 main.go create mode 100644 main_test.go create mode 100644 service.nix diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..c4a847d --- /dev/null +++ b/.gitignore @@ -0,0 +1 @@ +/result diff --git a/LICENSE b/LICENSE new file mode 100644 index 0000000..b8b8894 --- /dev/null +++ b/LICENSE @@ -0,0 +1,19 @@ +Copyright (c) 2026 Martin Fischer + +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. diff --git a/README.md b/README.md new file mode 100644 index 0000000..6611111 --- /dev/null +++ b/README.md @@ -0,0 +1,19 @@ +# web-feed-exporter + +Prometheus metrics for the most recently published timestamp of web feeds +(RSS, Atom or JSON), so your Grafana dashboard can remind you to post +to your blog or social media. + +## Provided metrics + +The following metrics are provided. All of them have a `feed` label containing the feed name. + +* `webfeed_items`, how many items the feed contains +* `webfeed_newest_published_timestamp_seconds`, Unix timestamp of the newest published item +* `webfeed_oldest_published_timestamp_seconds`, Unix timestamp of the oldest published item (that is still in the feed) + +## Limitations + +Feeds often contain only a limited number of the most recent items. +This exporter does not store anything so it also provides no metrics +for how many items were published in total or in specific time frames. diff --git a/default.nix b/default.nix new file mode 100644 index 0000000..61416cd --- /dev/null +++ b/default.nix @@ -0,0 +1,8 @@ +{ pkgs ? import {} }: + +pkgs.buildGoModule { + pname = "web-feed-exporter"; + version = "0+git"; + src = pkgs.lib.cleanSource ./.; + vendorHash = (import ./hashes.nix).vendor; +} diff --git a/go.mod b/go.mod new file mode 100644 index 0000000..c3d92e9 --- /dev/null +++ b/go.mod @@ -0,0 +1,31 @@ +module push-f.com/web-feed-exporter + +go 1.25.4 + +require ( + github.com/alecthomas/kong v1.13.0 + github.com/google/go-cmp v0.7.0 + github.com/mmcdole/gofeed v1.3.0 + github.com/prometheus/client_golang v1.23.2 + github.com/prometheus/common v0.66.1 +) + +require ( + github.com/PuerkitoBio/goquery v1.8.0 // indirect + github.com/andybalholm/cascadia v1.3.1 // indirect + github.com/beorn7/perks v1.0.1 // indirect + github.com/cespare/xxhash/v2 v2.3.0 // indirect + github.com/json-iterator/go v1.1.12 // indirect + github.com/kr/text v0.2.0 // indirect + github.com/mmcdole/goxpp v1.1.1-0.20240225020742-a0c311522b23 // indirect + github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect + github.com/modern-go/reflect2 v1.0.2 // indirect + github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect + github.com/prometheus/client_model v0.6.2 // indirect + github.com/prometheus/procfs v0.16.1 // indirect + go.yaml.in/yaml/v2 v2.4.2 // indirect + golang.org/x/net v0.43.0 // indirect + golang.org/x/sys v0.35.0 // indirect + golang.org/x/text v0.28.0 // indirect + google.golang.org/protobuf v1.36.8 // indirect +) diff --git a/go.sum b/go.sum new file mode 100644 index 0000000..e568b51 --- /dev/null +++ b/go.sum @@ -0,0 +1,83 @@ +github.com/PuerkitoBio/goquery v1.8.0 h1:PJTF7AmFCFKk1N6V6jmKfrNH9tV5pNE6lZMkG0gta/U= +github.com/PuerkitoBio/goquery v1.8.0/go.mod h1:ypIiRMtY7COPGk+I/YbZLbxsxn9g5ejnI2HSMtkjZvI= +github.com/alecthomas/assert/v2 v2.11.0 h1:2Q9r3ki8+JYXvGsDyBXwH3LcJ+WK5D0gc5E8vS6K3D0= +github.com/alecthomas/assert/v2 v2.11.0/go.mod h1:Bze95FyfUr7x34QZrjL+XP+0qgp/zg8yS+TtBj1WA3k= +github.com/alecthomas/kong v1.13.0 h1:5e/7XC3ugvhP1DQBmTS+WuHtCbcv44hsohMgcvVxSrA= +github.com/alecthomas/kong v1.13.0/go.mod h1:wrlbXem1CWqUV5Vbmss5ISYhsVPkBb1Yo7YKJghju2I= +github.com/alecthomas/repr v0.5.2 h1:SU73FTI9D1P5UNtvseffFSGmdNci/O6RsqzeXJtP0Qs= +github.com/alecthomas/repr v0.5.2/go.mod h1:Fr0507jx4eOXV7AlPV6AVZLYrLIuIeSOWtW57eE/O/4= 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new file mode 100644 index 0000000..3ecd26a --- /dev/null +++ b/hashes.nix @@ -0,0 +1,3 @@ +{ + vendor = "sha256-xNwlFPf8yg3Rbe9MWH05XNapyA1CFhhzy4jEB1VxGGQ="; +} diff --git a/main.go b/main.go new file mode 100644 index 0000000..94b040d --- /dev/null +++ b/main.go @@ -0,0 +1,144 @@ +package main + +import ( + "encoding/json" + "fmt" + "log/slog" + "math" + "net/http" + "net/url" + "os" + + "github.com/alecthomas/kong" + "github.com/mmcdole/gofeed" + "github.com/prometheus/client_golang/prometheus" + "github.com/prometheus/client_golang/prometheus/promhttp" +) + +type Args struct { + Port int `help:"Port to listen on" short:"p" default:"8888" env:"PORT"` + Feeds StringMap `placeholder:"{\"name\": \"url\", ...}" required:"" help:"Feeds to fetch" env:"FEEDS"` +} + +type StringMap map[string]string + +func (p *StringMap) UnmarshalJSON(data []byte) error { + stringMap := (*map[string]string)(p) + return json.Unmarshal(data, &stringMap) +} + +func main() { + logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{ + Level: slog.LevelDebug, + })) + slog.SetDefault(logger) + + var args Args + ctx := kong.Parse(&args, kong.Description( + "Prometheus metrics for the most/least recently published timestamp of web feeds (RSS, Atom or JSON).", + )) + + te, err := newExporter(args.Feeds, prometheus.DefaultRegisterer) + ctx.FatalIfErrorf(err) + + prometheus.MustRegister(te) + http.Handle("/metrics", promhttp.Handler()) + + slog.Info("starting", "urls", args.Feeds) + slog.Info(fmt.Sprintf("serving metrics at http://localhost:%d/metrics", args.Port)) + http.ListenAndServe(fmt.Sprintf(":%d", args.Port), nil) +} + +type Exporter struct { + urls map[string]string + itemCount *prometheus.Desc + newestPublishedTimestampSeconds *prometheus.Desc + oldestPublishedTimestampSeconds *prometheus.Desc +} + +func newExporter(feeds map[string]string, reg prometheus.Registerer) (*Exporter, error) { + if len(feeds) == 0 { + return nil, fmt.Errorf("provided feeds map is empty") + } + + for _, urlStr := range feeds { + url, err := url.Parse(urlStr) + if err != nil { + return nil, err + } + if url.Scheme != "http" && url.Scheme != "https" { + return nil, fmt.Errorf("unsupported protocol scheme %q (only http and https are supported)", url.Scheme) + } + } + + return &Exporter{ + urls: feeds, + itemCount: prometheus.NewDesc( + "webfeed_items", + "How many items the feed contains", + []string{"feed"}, + nil, + ), + newestPublishedTimestampSeconds: prometheus.NewDesc( + "webfeed_newest_published_timestamp_seconds", + "Unix timestamp of the newest published item", + []string{"feed"}, + nil, + ), + oldestPublishedTimestampSeconds: prometheus.NewDesc( + "webfeed_oldest_published_timestamp_seconds", + "Unix timestamp of the oldest published item (that is still in the feed)", + []string{"feed"}, + nil, + ), + }, nil +} + +func (e *Exporter) Describe(ch chan<- *prometheus.Desc) { + ch <- e.itemCount + ch <- e.newestPublishedTimestampSeconds + ch <- e.oldestPublishedTimestampSeconds +} + +func (e *Exporter) Collect(ch chan<- prometheus.Metric) { + for name, url := range e.urls { + e.collectFeed(name, url, ch) + } +} + +func (e *Exporter) collectFeed(name, url string, ch chan<- prometheus.Metric) { + feed, err := fetchFeed(url) + if err != nil { + slog.Error("failed to fetch feed", "url", url, "error", err) + return + } + + ch <- prometheus.MustNewConstMetric(e.itemCount, prometheus.GaugeValue, float64(len(feed.Items)), name) + + if len(feed.Items) == 0 { + return + } + + newestPublished := int64(-1) + oldestPublished := int64(math.MaxInt64) + + for _, item := range feed.Items { + if item.PublishedParsed != nil { + if item.PublishedParsed.Unix() > int64(newestPublished) { + newestPublished = item.PublishedParsed.Unix() + } + if item.PublishedParsed.Unix() < int64(oldestPublished) { + oldestPublished = item.PublishedParsed.Unix() + } + } + } + + ch <- prometheus.MustNewConstMetric(e.newestPublishedTimestampSeconds, prometheus.GaugeValue, float64(newestPublished), name) + ch <- prometheus.MustNewConstMetric(e.oldestPublishedTimestampSeconds, prometheus.GaugeValue, float64(oldestPublished), name) +} + +var fetchFeed = func(url string) (*gofeed.Feed, error) { + fp := gofeed.NewParser() + fp.UserAgent = "web-feed-exporter" + return fp.ParseURL(url) +} diff --git a/main_test.go b/main_test.go new file mode 100644 index 0000000..112798e --- /dev/null +++ b/main_test.go @@ -0,0 +1,90 @@ +package main + +import ( + "fmt" + "log" + "os" + "path" + "slices" + "strings" + "testing" + "time" + + "github.com/google/go-cmp/cmp" + "github.com/mmcdole/gofeed" + "github.com/prometheus/client_golang/prometheus" + "github.com/prometheus/common/expfmt" +) + +func TestGrepRepo(t *testing.T) { + reposDir := t.TempDir() + err := os.Mkdir(path.Join(reposDir, "project1"), 0o755) + if err != nil { + t.Fatal(err) + } + + feedUrl1 := "http://example.com/feed1.xml" + feedUrl2 := "http://example.com/feed2.xml" + + urls := map[string]string{"feed1": feedUrl1, "feed2": feedUrl2} + reg := prometheus.NewRegistry() + te, err := newExporter(urls, reg) + if err != nil { + t.Fatal(err) + } + reg.MustRegister(te) + + latestTimes := map[string][]int64{ + feedUrl1: {1700000000, 1900000000, 1300000000}, + feedUrl2: {1500000000}, + } + + fetchFeed = func(url string) (*gofeed.Feed, error) { + items := []*gofeed.Item{} + for _, sec := range latestTimes[url] { + time := time.Unix(sec, 0) + items = append(items, &gofeed.Item{ + PublishedParsed: &time, + }) + } + return &gofeed.Feed{ + Items: items, + }, nil + } + + want := "# HELP webfeed_items How many items the feed contains\n" + + "# TYPE webfeed_items gauge\n" + + fmt.Sprintf("webfeed_items{feed=\"feed1\"} %d\n", len(latestTimes[feedUrl1])) + + fmt.Sprintf("webfeed_items{feed=\"feed2\"} %d\n", len(latestTimes[feedUrl2])) + + "# HELP webfeed_newest_published_timestamp_seconds Unix timestamp of the newest published item\n" + + "# TYPE webfeed_newest_published_timestamp_seconds gauge\n" + + fmt.Sprintf("webfeed_newest_published_timestamp_seconds{feed=\"feed1\"} %.1e\n", float64(slices.Max(latestTimes[feedUrl1]))) + + fmt.Sprintf("webfeed_newest_published_timestamp_seconds{feed=\"feed2\"} %.1e\n", float64(slices.Max(latestTimes[feedUrl2]))) + + "# HELP webfeed_oldest_published_timestamp_seconds Unix timestamp of the oldest published item (that is still in the feed)\n" + + "# TYPE webfeed_oldest_published_timestamp_seconds gauge\n" + + fmt.Sprintf("webfeed_oldest_published_timestamp_seconds{feed=\"feed1\"} %.1e\n", float64(slices.Min(latestTimes[feedUrl1]))) + + fmt.Sprintf("webfeed_oldest_published_timestamp_seconds{feed=\"feed2\"} %.1e\n", float64(slices.Min(latestTimes[feedUrl2]))) + + if diff := cmp.Diff(collectMetrics(reg), want); diff != "" { + t.Errorf("unexpected metrics: %v", diff) + } +} + +func collectMetrics(reg *prometheus.Registry) string { + mfs, done, err := prometheus.ToTransactionalGatherer(reg).Gather() + if err != nil { + log.Fatal(err) + } + defer done() + + var buf strings.Builder + enc := expfmt.NewEncoder(&buf, expfmt.NewFormat(expfmt.TypeTextPlain)) + + for _, mf := range mfs { + err := enc.Encode(mf) + if err != nil { + log.Fatal(err) + } + } + return buf.String() +} diff --git a/service.nix b/service.nix new file mode 100644 index 0000000..1942107 --- /dev/null +++ b/service.nix @@ -0,0 +1,35 @@ +{ config, lib, pkgs, ... }: + +let + web_feed_exporter = pkgs.callPackage ./default.nix {}; + cfg = config.services.webFeedExporter; +in +{ + options.services.webFeedExporter = { + enable = lib.mkEnableOption "web-feed-exporter"; + + port = lib.mkOption { + type = lib.types.int; + }; + + feeds = lib.mkOption { + type = lib.types.attrsOf lib.types.str; + description = "Map of feed names to feed URLs."; + }; + }; + + config = lib.mkIf cfg.enable { + systemd.services.web-feed-exporter = { + serviceConfig = { + DynamicUser = true; + ExecStart = "${web_feed_exporter}/bin/web-feed-exporter"; + }; + environment = { + PORT = toString cfg.port; + FEEDS = builtins.toJSON cfg.feeds; + }; + + wantedBy = ["multi-user.target"]; + }; + }; +} -- cgit v1.3.1