first commit

listeners/http_stats.go

@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: 2023 mysubarumq
+// SPDX-FileContributor: alex-savin
+
+package listeners
+
+import (
+	"context"
+	"encoding/json"
+	"io"
+	"log/slog"
+	"net/http"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"git.savin.nyc/alex/mysubaru-mq/system"
+)
+
+// HTTPStats is a listener for presenting the server $SYS stats on a JSON http endpoint.
+type HTTPStats struct {
+	sync.RWMutex
+	id      string       // the internal id of the listener
+	address string       // the network address to bind to
+	config  *Config      // configuration values for the listener
+	listen  *http.Server // the http server
+	sysInfo *system.Info // pointers to the server data
+	log     *slog.Logger // server logger
+	end     uint32       // ensure the close methods are only called once
+}
+
+// NewHTTPStats initialises and returns a new HTTP listener, listening on an address.
+func NewHTTPStats(id, address string, config *Config, sysInfo *system.Info) *HTTPStats {
+	if config == nil {
+		config = new(Config)
+	}
+	return &HTTPStats{
+		id:      id,
+		address: address,
+		sysInfo: sysInfo,
+		config:  config,
+	}
+}
+
+// ID returns the id of the listener.
+func (l *HTTPStats) ID() string {
+	return l.id
+}
+
+// Address returns the address of the listener.
+func (l *HTTPStats) Address() string {
+	return l.address
+}
+
+// Protocol returns the address of the listener.
+func (l *HTTPStats) Protocol() string {
+	if l.listen != nil && l.listen.TLSConfig != nil {
+		return "https"
+	}
+
+	return "http"
+}
+
+// Init initializes the listener.
+func (l *HTTPStats) Init(log *slog.Logger) error {
+	l.log = log
+	mux := http.NewServeMux()
+	mux.HandleFunc("/", l.jsonHandler)
+	l.listen = &http.Server{
+		ReadTimeout:  5 * time.Second,
+		WriteTimeout: 5 * time.Second,
+		Addr:         l.address,
+		Handler:      mux,
+	}
+
+	if l.config.TLSConfig != nil {
+		l.listen.TLSConfig = l.config.TLSConfig
+	}
+
+	return nil
+}
+
+// Serve starts listening for new connections and serving responses.
+func (l *HTTPStats) Serve() {
+
+	var err error
+	if l.listen.TLSConfig != nil {
+		err = l.listen.ListenAndServeTLS("", "")
+	} else {
+		err = l.listen.ListenAndServe()
+	}
+
+	// After the listener has been shutdown, no need to print the http.ErrServerClosed error.
+	if err != nil && atomic.LoadUint32(&l.end) == 0 {
+		l.log.Error("failed to serve.", "error", err, "listener", l.id)
+	}
+}
+
+// Close closes the listener and any client connections.
+func (l *HTTPStats) Close() {
+	l.Lock()
+	defer l.Unlock()
+
+	if atomic.CompareAndSwapUint32(&l.end, 0, 1) {
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		_ = l.listen.Shutdown(ctx)
+	}
+
+	// closeClients(l.id)
+}
+
+// jsonHandler is an HTTP handler which outputs the $SYS stats as JSON.
+func (l *HTTPStats) jsonHandler(w http.ResponseWriter, req *http.Request) {
+	info := *l.sysInfo.Clone()
+
+	out, err := json.MarshalIndent(info, "", "\t")
+	if err != nil {
+		_, _ = io.WriteString(w, err.Error())
+	}
+
+	_, _ = w.Write(out)
+}