From d847c71a509dde358a8772c5ba15e756399734d3 Mon Sep 17 00:00:00 2001 From: Pierre-Olivier Mercier Date: Thu, 23 Apr 2026 10:06:48 +0700 Subject: [PATCH 01/11] checker: let CheckRule.Evaluate return per-subject CheckStates MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Rules that iterate over multiple elements (certificates, CAA records, nameservers, …) previously had to squash per-element results into a single concatenated message. Evaluate now returns []CheckState and CheckState carries an opaque Subject, so each element gets its own structured state. The server injects a StatusUnknown placeholder when a rule returns nothing, to avoid silently dropping the rule. --- checker/server.go | 16 ++++++++++++---- checker/server_test.go | 4 ++-- checker/types.go | 19 ++++++++++++++++--- 3 files changed, 30 insertions(+), 9 deletions(-) diff --git a/checker/server.go b/checker/server.go index 8b2eb31..444c118 100644 --- a/checker/server.go +++ b/checker/server.go @@ -291,11 +291,19 @@ func (s *Server) handleEvaluate(w http.ResponseWriter, r *http.Request) { continue } } - state := rule.Evaluate(r.Context(), obs, req.Options) - if state.Code == "" { - state.Code = rule.Name() + ruleStates := rule.Evaluate(r.Context(), obs, req.Options) + if len(ruleStates) == 0 { + ruleStates = []CheckState{{ + Status: StatusUnknown, + Message: fmt.Sprintf("rule %q returned no state", rule.Name()), + }} + } + for _, state := range ruleStates { + if state.Code == "" { + state.Code = rule.Name() + } + states = append(states, state) } - states = append(states, state) } writeJSON(w, http.StatusOK, ExternalEvaluateResponse{States: states}) diff --git a/checker/server_test.go b/checker/server_test.go index 6a228b6..23ac446 100644 --- a/checker/server_test.go +++ b/checker/server_test.go @@ -65,8 +65,8 @@ type dummyRule struct { func (r *dummyRule) Name() string { return r.name } func (r *dummyRule) Description() string { return r.desc } -func (r *dummyRule) Evaluate(ctx context.Context, obs ObservationGetter, opts CheckerOptions) CheckState { - return CheckState{Status: StatusOK, Message: r.name + " passed"} +func (r *dummyRule) Evaluate(ctx context.Context, obs ObservationGetter, opts CheckerOptions) []CheckState { + return []CheckState{{Status: StatusOK, Message: r.name + " passed"}} } // --- helpers --- diff --git a/checker/types.go b/checker/types.go index 9099a2f..2600987 100644 --- a/checker/types.go +++ b/checker/types.go @@ -182,11 +182,15 @@ func (s Status) String() string { } } -// CheckState is the result of evaluating a single rule. +// CheckState is the result of evaluating a single rule on a single subject. +// Subject is opaque to the SDK: producers and consumers agree on its shape +// (a hostname, a record key, a serial, …). Leave Subject empty for rules +// that produce a single, global result. type CheckState struct { Status Status `json:"status"` Message string `json:"message"` Code string `json:"code,omitempty"` + Subject string `json:"subject,omitempty"` Meta map[string]any `json:"meta,omitempty"` } @@ -222,11 +226,20 @@ type CheckRuleInfo struct { Options *CheckerOptionsDocumentation `json:"options,omitempty"` } -// CheckRule evaluates observations and produces a CheckState. +// CheckRule evaluates observations and produces one or more CheckStates. +// +// Evaluate returns a slice so a rule iterating over multiple elements can +// emit one state per subject (each carrying CheckState.Subject) without +// squashing them into a single concatenated message. +// +// Evaluate must not return a nil or empty slice: callers expect at least +// one state per rule. When a rule finds nothing to evaluate, return a +// single CheckState with an appropriate status (typically StatusInfo or +// StatusOK) describing that fact. type CheckRule interface { Name() string Description() string - Evaluate(ctx context.Context, obs ObservationGetter, opts CheckerOptions) CheckState + Evaluate(ctx context.Context, obs ObservationGetter, opts CheckerOptions) []CheckState } // CheckRuleWithOptions is an optional interface that rules can implement From 0c6a886e8272c07db9c79703ba0213b13a6f2ca9 Mon Sep 17 00:00:00 2001 From: Pierre-Olivier Mercier Date: Thu, 23 Apr 2026 10:12:55 +0700 Subject: [PATCH 02/11] server: expose Handle/HandleFunc for custom checker routes Lets plugins register auxiliary endpoints (debug pages, webhooks, UI assets) on the SDK mux, with TrackWork as an opt-in for the /health load signal. --- README.md | 26 ++++++++++++++++++++++++++ checker/server.go | 35 ++++++++++++++++++++++++----------- 2 files changed, 50 insertions(+), 11 deletions(-) diff --git a/README.md b/README.md index ed5f3f6..7f47eb8 100644 --- a/README.md +++ b/README.md @@ -30,6 +30,32 @@ go get git.happydns.org/checker-sdk-go/checker See [checker-dummy](https://git.happydns.org/checker-dummy) for a fully working, documented template. +## Extending the server + +`checker.Server` exposes the standard SDK routes (`/health`, `/collect`, +and, depending on the provider's optional interfaces, `/definition`, +`/evaluate`, `/report`). Plugins that need to serve auxiliary endpoints +(debug pages, webhooks, custom UI assets, …) can register them on the +same mux: + +```go +srv := checker.NewServer(provider) + +srv.HandleFunc("GET /debug/state", func(w http.ResponseWriter, r *http.Request) { + // … +}) + +// Opt a custom route into the in-flight / load-average signal +// reported on /health: +srv.Handle("POST /webhook", srv.TrackWork(myWebhookHandler)) + +log.Fatal(srv.ListenAndServe(":8080")) +``` + +Patterns that collide with built-in routes panic at registration — +pick non-overlapping paths. Custom handlers are not wrapped by the +load-tracking middleware unless you opt in via `TrackWork`. + ## License Apache License 2.0. See [LICENSE](LICENSE) and [NOTICE](NOTICE). diff --git a/checker/server.go b/checker/server.go index 444c118..6163497 100644 --- a/checker/server.go +++ b/checker/server.go @@ -111,19 +111,21 @@ func NewServer(provider ObservationProvider) *Server { } s.mux = http.NewServeMux() s.mux.HandleFunc("GET /health", s.handleHealth) - s.mux.Handle("POST /collect", s.trackWork(http.HandlerFunc(s.handleCollect))) + s.mux.Handle("POST /collect", s.TrackWork(http.HandlerFunc(s.handleCollect))) if dp, ok := provider.(CheckerDefinitionProvider); ok { - s.definition = dp.Definition() - s.definition.BuildRulesInfo() - s.mux.HandleFunc("GET /definition", s.handleDefinition) - s.mux.Handle("POST /evaluate", s.trackWork(http.HandlerFunc(s.handleEvaluate))) + if def := dp.Definition(); def != nil { + s.definition = def + s.definition.BuildRulesInfo() + s.mux.HandleFunc("GET /definition", s.handleDefinition) + s.mux.Handle("POST /evaluate", s.TrackWork(http.HandlerFunc(s.handleEvaluate))) + } } if _, ok := provider.(CheckerHTMLReporter); ok { - s.mux.Handle("POST /report", s.trackWork(http.HandlerFunc(s.handleReport))) + s.mux.Handle("POST /report", s.TrackWork(http.HandlerFunc(s.handleReport))) } else if _, ok := provider.(CheckerMetricsReporter); ok { - s.mux.Handle("POST /report", s.trackWork(http.HandlerFunc(s.handleReport))) + s.mux.Handle("POST /report", s.TrackWork(http.HandlerFunc(s.handleReport))) } go s.runSampler(ctx) @@ -137,6 +139,18 @@ func (s *Server) Handler() http.Handler { return requestLogger(s.mux) } +// Handle registers an auxiliary handler on the server's mux. Must be called +// before ListenAndServe or Handler(). Custom handlers are not tracked by +// TrackWork; wrap them explicitly if you want them counted in /health load. +func (s *Server) Handle(pattern string, handler http.Handler) { + s.mux.Handle(pattern, handler) +} + +// HandleFunc is the http.HandlerFunc-flavoured counterpart of Handle. +func (s *Server) HandleFunc(pattern string, handler func(http.ResponseWriter, *http.Request)) { + s.mux.HandleFunc(pattern, handler) +} + // ListenAndServe starts the HTTP server on the given address. // // ListenAndServe does not stop the background load-average sampler on return; @@ -158,10 +172,9 @@ func (s *Server) Close() error { return nil } -// trackWork wraps a handler with in-flight and total-request accounting. -// It is applied only to "work" endpoints (/collect, /evaluate, /report) so -// that /health polling traffic does not pollute the load signal. -func (s *Server) trackWork(next http.Handler) http.Handler { +// TrackWork wraps a handler with in-flight and total-request accounting, +// opting custom routes into the load signal reported on /health. +func (s *Server) TrackWork(next http.Handler) http.Handler { return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { s.inFlight.Add(1) s.totalRequests.Add(1) From 199c7dea3fc3d305bdcf523ca6a9438cb12206fb Mon Sep 17 00:00:00 2001 From: Pierre-Olivier Mercier Date: Thu, 23 Apr 2026 11:20:29 +0700 Subject: [PATCH 03/11] checker: add /check route for standalone human-facing web UI Providers that implement the new CheckerInteractive interface (RenderForm + ParseForm) get a built-in HTML form on GET /check and a consolidated result page on POST /check that runs the standard Collect -> Evaluate -> GetHTMLReport / ExtractMetrics pipeline. This lets a checker be used directly from a browser outside of happyDomain, with the checker itself resolving what the host would normally auto-fill (typically via its own DNS queries). Also guards NewServer against a nil Definition() so providers that advertise CheckerDefinitionProvider without a ready definition no longer panic at registration. --- README.md | 21 +++ checker/interactive.go | 347 ++++++++++++++++++++++++++++++++++++ checker/interactive_test.go | 245 +++++++++++++++++++++++++ checker/server.go | 49 +++-- 4 files changed, 644 insertions(+), 18 deletions(-) create mode 100644 checker/interactive.go create mode 100644 checker/interactive_test.go diff --git a/README.md b/README.md index 7f47eb8..e224fdf 100644 --- a/README.md +++ b/README.md @@ -56,6 +56,27 @@ Patterns that collide with built-in routes panic at registration — pick non-overlapping paths. Custom handlers are not wrapped by the load-tracking middleware unless you opt in via `TrackWork`. +## Standalone human UI (`/check`) + +Providers that implement `CheckerInteractive` get a built-in human-facing +web form on `/check`, usable outside of happyDomain: + +```go +type CheckerInteractive interface { + RenderForm() []CheckerOptionField + ParseForm(r *http.Request) (CheckerOptions, error) +} +``` + +- `GET /check` renders a form derived from `RenderForm()`. +- `POST /check` calls `ParseForm` to obtain `CheckerOptions`, runs the + standard `Collect` → `Evaluate` → `GetHTMLReport` / `ExtractMetrics` + pipeline, and returns a consolidated HTML page. + +`ParseForm` is where the checker replaces what happyDomain would normally +auto-fill (zone records, service payload, …) — typically by issuing its +own DNS queries from the human-supplied inputs. + ## License Apache License 2.0. See [LICENSE](LICENSE) and [NOTICE](NOTICE). diff --git a/checker/interactive.go b/checker/interactive.go new file mode 100644 index 0000000..b3473bc --- /dev/null +++ b/checker/interactive.go @@ -0,0 +1,347 @@ +// Copyright 2020-2026 The happyDomain 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. + +package checker + +import ( + "bytes" + "encoding/json" + "fmt" + "html/template" + "log" + "net/http" + "time" +) + +// CheckerInteractive is an optional interface that observation providers +// can implement to expose a human-facing web form usable standalone, +// outside of a happyDomain host. Detect support with a type assertion: +// _, ok := provider.(CheckerInteractive). +// +// When the provider implements it, Server binds GET and POST on /check. +// GET renders an HTML form built from RenderForm(). POST calls ParseForm +// to obtain the CheckerOptions, then runs the standard pipeline +// (Collect, Evaluate, GetHTMLReport, ExtractMetrics) and renders a +// consolidated result page. +// +// Unlike /evaluate, which relies on happyDomain to fill AutoFill-backed +// options from execution context, a CheckerInteractive implementation is +// responsible for resolving whatever it needs from the human inputs +// (typically via direct DNS queries) before Collect runs. +type CheckerInteractive interface { + // RenderForm returns the fields the human must fill in to bootstrap + // a check. Typically a minimal set (domain name, nameserver to + // query, …) that ParseForm expands into the full CheckerOptions + // that Collect expects. + RenderForm() []CheckerOptionField + + // ParseForm reads the submitted form and returns the CheckerOptions + // ready to feed Collect. It is the checker's responsibility to do + // whatever lookups or resolutions are needed to populate fields + // that would normally be auto-filled by happyDomain. Returning an + // error causes the SDK to re-render the form with the error + // displayed. + ParseForm(r *http.Request) (CheckerOptions, error) +} + +// checkResult holds everything the result page needs to render. +type checkResult struct { + Title string + States []CheckState + Metrics []CheckMetric + ReportHTML string + CollectErr string + ReportErr string + MetricsErr string +} + +type checkFormPage struct { + Title string + Fields []CheckerOptionField + Error string +} + +func (s *Server) handleCheckForm(w http.ResponseWriter, r *http.Request) { + s.renderCheckForm(w, s.interactive.RenderForm(), "") +} + +func (s *Server) handleCheckSubmit(w http.ResponseWriter, r *http.Request) { + if err := r.ParseForm(); err != nil { + s.renderCheckForm(w, s.interactive.RenderForm(), fmt.Sprintf("invalid form: %v", err)) + return + } + + opts, err := s.interactive.ParseForm(r) + if err != nil { + s.renderCheckForm(w, s.interactive.RenderForm(), err.Error()) + return + } + + result := &checkResult{Title: s.checkPageTitle()} + + data, err := s.provider.Collect(r.Context(), opts) + if err != nil { + result.CollectErr = err.Error() + s.renderCheckResult(w, result) + return + } + + raw, err := json.Marshal(data) + if err != nil { + result.CollectErr = fmt.Sprintf("failed to marshal collected data: %v", err) + s.renderCheckResult(w, result) + return + } + + if s.definition != nil { + obs := &mapObservationGetter{data: map[ObservationKey]json.RawMessage{ + s.provider.Key(): raw, + }} + result.States = s.evaluateRules(r.Context(), obs, opts, nil) + } + + ctx := NewReportContext(raw, nil) + + if reporter, ok := s.provider.(CheckerHTMLReporter); ok { + html, rerr := reporter.GetHTMLReport(ctx) + if rerr != nil { + result.ReportErr = rerr.Error() + } else { + result.ReportHTML = html + } + } + + if reporter, ok := s.provider.(CheckerMetricsReporter); ok { + metrics, merr := reporter.ExtractMetrics(ctx, time.Now()) + if merr != nil { + result.MetricsErr = merr.Error() + } else { + result.Metrics = metrics + } + } + + s.renderCheckResult(w, result) +} + +func (s *Server) checkPageTitle() string { + if s.definition != nil && s.definition.Name != "" { + return s.definition.Name + } + return "Checker" +} + +func renderHTML(w http.ResponseWriter, status int, tpl *template.Template, data any) { + var buf bytes.Buffer + if err := tpl.Execute(&buf, data); err != nil { + log.Printf("render %s: %v", tpl.Name(), err) + http.Error(w, "failed to render page", http.StatusInternalServerError) + return + } + w.Header().Set("Content-Type", "text/html; charset=utf-8") + w.WriteHeader(status) + w.Write(buf.Bytes()) +} + +func (s *Server) renderCheckForm(w http.ResponseWriter, fields []CheckerOptionField, errMsg string) { + status := http.StatusOK + if errMsg != "" { + status = http.StatusBadRequest + } + renderHTML(w, status, checkFormTemplate, checkFormPage{ + Title: s.checkPageTitle(), + Fields: fields, + Error: errMsg, + }) +} + +func (s *Server) renderCheckResult(w http.ResponseWriter, result *checkResult) { + renderHTML(w, http.StatusOK, checkResultTemplate, result) +} + +func statusClass(s Status) string { + switch s { + case StatusOK: + return "ok" + case StatusInfo: + return "info" + case StatusWarn: + return "warn" + case StatusCrit: + return "crit" + case StatusError: + return "error" + default: + return "unknown" + } +} + +// defaultString avoids printing the literal "" for unset defaults. +func defaultString(v any) string { + if v == nil { + return "" + } + switch t := v.(type) { + case string: + return t + case bool: + if t { + return "true" + } + return "" + default: + return fmt.Sprintf("%v", v) + } +} + +func defaultBool(v any) bool { + b, _ := v.(bool) + return b +} + +var templateFuncs = template.FuncMap{ + "statusClass": statusClass, + "statusString": Status.String, + "defaultString": defaultString, + "defaultBool": defaultBool, +} + +const baseCSS = ` +body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif; max-width: 960px; margin: 2rem auto; padding: 0 1rem; color: #222; } +h1, h2 { border-bottom: 1px solid #eee; padding-bottom: 0.3rem; } +form { display: grid; gap: 1rem; } +label { display: block; font-weight: 600; margin-bottom: 0.25rem; } +.required::after { content: " *"; color: #c00; } +.desc { font-weight: normal; color: #666; font-size: 0.9rem; display: block; margin-top: 0.1rem; } +input[type=text], input[type=password], input[type=number], select, textarea { + width: 100%; padding: 0.5rem; border: 1px solid #bbb; border-radius: 4px; box-sizing: border-box; font: inherit; +} +textarea { min-height: 6rem; } +button { padding: 0.6rem 1.2rem; background: #0b63c5; color: #fff; border: 0; border-radius: 4px; font: inherit; cursor: pointer; } +button:hover { background: #084c98; } +.err { background: #fee; border: 1px solid #fbb; color: #900; padding: 0.6rem 0.8rem; border-radius: 4px; margin: 1rem 0; } +table { border-collapse: collapse; width: 100%; margin: 0.5rem 0 1.5rem; } +th, td { text-align: left; padding: 0.5rem 0.6rem; border-bottom: 1px solid #eee; vertical-align: top; } +th { background: #f7f7f7; } +.badge { display: inline-block; padding: 0.15rem 0.5rem; border-radius: 3px; font-size: 0.8rem; font-weight: 600; color: #fff; } +.badge.ok { background: #2a9d3c; } +.badge.info { background: #3277cc; } +.badge.warn { background: #d08a00; } +.badge.crit { background: #c0392b; } +.badge.error { background: #7a1f1f; } +.badge.unknown { background: #777; } +iframe.report { width: 100%; min-height: 480px; border: 1px solid #ccc; border-radius: 4px; } +.actions { margin-top: 1.5rem; } +.actions a { color: #0b63c5; text-decoration: none; } +.actions a:hover { text-decoration: underline; } +` + +var checkFormTemplate = template.Must(template.New("form").Funcs(templateFuncs).Parse(` + + + +{{.Title}} – Check + + + +

{{.Title}}

+{{if .Error}}
{{.Error}}
{{end}} +
+{{range .Fields}}{{if not .Hide}} +
+ + {{if .Choices}} + + {{else if eq .Type "bool"}} + + {{else if .Textarea}} + + {{else if eq .Type "number"}} + + {{else if eq .Type "uint"}} + + {{else if .Secret}} + + {{else}} + + {{end}} +
+{{end}}{{end}} +
+
+ +`)) + +var checkResultTemplate = template.Must(template.New("result").Funcs(templateFuncs).Parse(` + + + +{{.Title}} – Result + + + +

{{.Title}}

+ +{{if .CollectErr}}
Collect failed: {{.CollectErr}}
{{end}} + +{{if .States}} +

Check states

+ + + + {{range .States}} + + + + + + + {{end}} + +
StatusCodeSubjectMessage
{{statusString .Status}}{{.Code}}{{.Subject}}{{.Message}}
+{{end}} + +{{if .Metrics}} +

Metrics

+ + + + {{range .Metrics}} + + + + + + + {{end}} + +
NameValueUnitLabels
{{.Name}}{{.Value}}{{.Unit}}{{range $k, $v := .Labels}}{{$k}}={{$v}} {{end}}
+{{end}} + +{{if .MetricsErr}}
Metrics error: {{.MetricsErr}}
{{end}} + +{{if .ReportHTML}} +

Report

+ +{{end}} + +{{if .ReportErr}}
Report error: {{.ReportErr}}
{{end}} + +
← Run another check
+ +`)) diff --git a/checker/interactive_test.go b/checker/interactive_test.go new file mode 100644 index 0000000..0a48512 --- /dev/null +++ b/checker/interactive_test.go @@ -0,0 +1,245 @@ +// Copyright 2020-2026 The happyDomain 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. + +package checker + +import ( + "context" + "errors" + "net/http" + "net/http/httptest" + "net/url" + "strings" + "testing" +) + +// interactiveProvider embeds testProvider and adds CheckerInteractive. +type interactiveProvider struct { + *testProvider + fields []CheckerOptionField + parseFn func(r *http.Request) (CheckerOptions, error) + parseErr error +} + +func (p *interactiveProvider) RenderForm() []CheckerOptionField { + return p.fields +} + +func (p *interactiveProvider) ParseForm(r *http.Request) (CheckerOptions, error) { + if p.parseErr != nil { + return nil, p.parseErr + } + if p.parseFn != nil { + return p.parseFn(r) + } + return CheckerOptions{"domain": r.FormValue("domain")}, nil +} + +func postForm(handler http.Handler, path string, values url.Values) *httptest.ResponseRecorder { + req := httptest.NewRequest("POST", path, strings.NewReader(values.Encode())) + req.Header.Set("Content-Type", "application/x-www-form-urlencoded") + rec := httptest.NewRecorder() + handler.ServeHTTP(rec, req) + return rec +} + +// minimalProvider implements only ObservationProvider. +type minimalProvider struct{ key ObservationKey } + +func (m *minimalProvider) Key() ObservationKey { return m.key } +func (m *minimalProvider) Collect(ctx context.Context, opts CheckerOptions) (any, error) { + return nil, nil +} + +func TestCheck_NotRegistered_WhenProviderLacksInterface(t *testing.T) { + p := &minimalProvider{key: "test"} + srv := NewServer(p) + defer srv.Close() + + rec := doRequest(srv.Handler(), "GET", "/check", nil, nil) + if rec.Code != http.StatusNotFound { + t.Fatalf("GET /check without CheckerInteractive = %d, want 404", rec.Code) + } +} + +func TestCheck_Form_Renders(t *testing.T) { + p := &interactiveProvider{ + testProvider: &testProvider{key: "test"}, + fields: []CheckerOptionField{ + {Id: "domain", Type: "string", Label: "Domain name", Required: true, Placeholder: "example.com"}, + {Id: "verbose", Type: "bool", Label: "Verbose", Default: true}, + {Id: "flavor", Type: "string", Choices: []string{"a", "b"}, Default: "b"}, + {Id: "hidden", Type: "string", Hide: true}, + }, + } + srv := NewServer(p) + defer srv.Close() + + rec := doRequest(srv.Handler(), "GET", "/check", nil, nil) + if rec.Code != http.StatusOK { + t.Fatalf("GET /check = %d, want 200", rec.Code) + } + body := rec.Body.String() + for _, want := range []string{ + `name="domain"`, + `placeholder="example.com"`, + `Domain name`, + `type="checkbox"`, + `name="verbose"`, + ` checked`, + `