feat: accept new SLO specs using the filesystem HTTP api

README.md

@@ -186,6 +186,23 @@ picked up by a Prometheus instance. While running Pyrra on its own works, there
 won't be any SLO configured, nor will there be any data from a Prometheus to
 work with. It's designed to work alongside a Prometheus.
 
+SLO specs may be published using the `/specs/create` endpoint. This will cause `pyrra` to
+generate the corresponding recordingRules, write them out to disk and trigger a reload
+of Prometheus.
+
+Example:
+```
+% curl -i -X POST -H "content-type: multipart/form-data" -F "spec=@service-levels/some-slo.yaml" http://localhost:9444/ingest
+HTTP/1.1 200 OK
+Date: Fri, 15 Sep 2023 14:21:54 GMT
+Content-Length: 2
+Content-Type: text/plain; charset=utf-8
+
+ok
+```
+
+Note: the specs endpoint does not require authentication and needs to be explicitly enabled using `--specs-api`.
+
 ## Tech Stack
 
 **Client:** TypeScript with React, Bootstrap, and uPlot.

filesystem.go

@@ -3,6 +3,7 @@
 import (
 	"context"
 	"fmt"
+	"io"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -89,7 +90,140 @@
 	return objectives
 }
 
-func cmdFilesystem(logger log.Logger, reg *prometheus.Registry, promClient api.Client, configFiles, prometheusFolder string, genericRules bool) int {
+func _listFolderContents(folderPath string, w http.ResponseWriter) error {
+	err := filepath.Walk(folderPath, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		if info.IsDir() {
+			return nil
+		}
+		fmt.Fprintf(w, "%v\n", filepath.Base(path))
+		return nil
+	})
+	return err
+}
+
+func listSpecsHandler(logger log.Logger, specsDir string, prometheusDir string) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodGet {
+			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+			return
+		}
+		level.Info(logger).Log("msg", "listing available specs", "dir", specsDir)
+		fmt.Fprintf(w, "Specs currently available:\n")
+
+		err := _listFolderContents(specsDir, w)
+		if err != nil {
+			level.Error(logger).Log("msg", "error listing available specs", "err", err)
+		}
+
+		level.Info(logger).Log("msg", "listing generated rules", "dir", prometheusDir)
+		fmt.Fprintf(w, "Rules currently generated:\n")
+
+		err = _listFolderContents(prometheusDir, w)
+		if err != nil {
+			level.Error(logger).Log("msg", "error listing generated rules", "err", err)
+		}
+	}
+}
+
+func createSpecHandler(logger log.Logger, dir string, prometheusFolder string, reload chan struct{}, genericRules bool) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPost {
+			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+			return
+		}
+
+		r.ParseMultipartForm(32 << 20)
+		file, handler, err := r.FormFile("spec")
+		if err != nil {
+			http.Error(w, "Failure reading spec field in form upload: "+err.Error(), 400)
+			return
+		}
+
+		level.Info(logger).Log("msg", "processing SLO spec", "specFile", handler.Filename)
+
+		if err != nil {
+			level.Error(logger).Log("msg", "failed to process HTTP request", "err", err)
+			http.Error(w, "Failure: "+err.Error(), 400)
+			return
+		}
+
+		var ingestedSpec = dir + "/" + handler.Filename
+
+		level.Info(logger).Log("msg", "writing spec to disk", "location", ingestedSpec)
+		f, err := os.OpenFile(ingestedSpec, os.O_WRONLY|os.O_CREATE, 0666)
+		if err != nil {
+			level.Error(logger).Log("msg", "failed to write spec to disk", "err", err)
+			http.Error(w, "Failure: "+err.Error(), 500)
+			return
+		}
+		defer f.Close()
+
+		io.Copy(f, file)
+
+		level.Info(logger).Log("msg", "attempting to build rules from spec", "location", ingestedSpec)
+		err = writeRuleFile(logger, ingestedSpec, prometheusFolder, genericRules, false)
+		if err != nil {
+			level.Error(logger).Log("msg", "error building rules from spec", "file", ingestedSpec, "err", err)
+			http.Error(w, "Failure: "+err.Error(), 400)
+
+			err := os.Remove(ingestedSpec)
+			if err != nil {
+				level.Error(logger).Log("msg", "failed to remove spec", "file", ingestedSpec, "err", err)
+			}
+			return
+		}
+
+		level.Info(logger).Log("msg", "signaling Prometheus reload")
+		reload <- struct{}{}
+
+		fmt.Fprintf(w, "ok")
+	}
+}
+
+func removeSpecHandler(logger log.Logger, dir string, prometheusFolder string, reload chan struct{}) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodDelete {
+			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+			return
+		}
+
+		filePath := r.URL.Query().Get("f")
+		if filePath == "" {
+			http.Error(w, "Missing 'f' parameter in the query", http.StatusBadRequest)
+			return
+		}
+
+		cleanPath := filepath.Clean(filePath)
+
+		level.Info(logger).Log("msg", "removing for", "file", filePath)
+
+		level.Debug(logger).Log("msg", "removing spec", "file", filePath, "dir", dir)
+		err := os.Remove(dir + "/" + cleanPath)
+		if err != nil {
+			level.Error(logger).Log("msg", "failed to remove file", "file", filePath, "clean", cleanPath, "err", err)
+			http.Error(w, fmt.Sprintf("Error deleting spec: %s", err), http.StatusInternalServerError)
+			return
+		}
+
+		level.Debug(logger).Log("msg", "removing generated rules", "file", filePath, "dir", prometheusFolder)
+		err = os.Remove(prometheusFolder + "/" + cleanPath)
+		if err != nil {
+			level.Error(logger).Log("msg", "failed to remove Prometheus rules file", "file", filePath, "clean", cleanPath, "err", err)
+			http.Error(w, fmt.Sprintf("Error deleting rules: %s", err), http.StatusInternalServerError)
+			return
+		}
+
+		level.Info(logger).Log("msg", "signaling Prometheus reload")
+		reload <- struct{}{}
+
+		fmt.Fprintf(w, "ok")
+	}
+}
+
+func cmdFilesystem(logger log.Logger, reg *prometheus.Registry, promClient api.Client, configFiles, prometheusFolder string, specsApi bool, genericRules bool) int {
 	reconcilesTotal := prometheus.NewCounter(prometheus.CounterOpts{
 		Name: "pyrra_filesystem_reconciles_total",
 		Help: "The total amount of reconciles.",
@@ -122,7 +256,7 @@
 			}
 			<-ctx.Done()
 			return nil
 		}, func(err error) {
 			cancel()
 		})
 	}
@@ -242,6 +376,7 @@
 	}
 	{
 		prometheusInterceptor := connectprometheus.NewInterceptor(reg)
+		dir := filepath.Dir(configFiles)
 
 		router := http.NewServeMux()
 		router.Handle(objectivesv1alpha1connect.NewObjectiveBackendServiceHandler(
@@ -252,6 +387,15 @@
 		))
 		router.Handle("/metrics", promhttp.HandlerFor(reg, promhttp.HandlerOpts{}))
 
+		if specsApi {
+			level.Info(logger).Log("msg", "specs API endpoints are enabled")
+			router.HandleFunc("/specs/remove", removeSpecHandler(logger, dir, prometheusFolder, reload))
+			router.HandleFunc("/specs/create", createSpecHandler(logger, dir, prometheusFolder, reload, genericRules))
+			router.HandleFunc("/specs/list", listSpecsHandler(logger, dir, prometheusFolder))
+		} else {
+			level.Info(logger).Log("msg", "specs API endpoints are disabled")
+		}
+
 		server := http.Server{
 			Addr:    ":9444",
 			Handler: h2c.NewHandler(router, &http2.Server{}),