Add health check

.gitignore

@@ -1,2 +1,3 @@
 irccat
 irccat.json
+health.timestamp

Dockerfile

@@ -21,8 +21,12 @@ RUN CGO_ENABLED=0 go get -t -v ./... && go build -a .
 # Step two: copy over the binary and root certs
 FROM scratch
 COPY --from=build /go/bin/irccat /irccat
+COPY --from=build /go/bin/healthcheck /healthcheck
 COPY --from=build /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
 
+# Docker-only (no OCI)
+HEALTHCHECK --interval=60s --timeout=10s --start-period=600s CMD ["/healthcheck"]
+
 EXPOSE 12345
 EXPOSE 8045
 

examples/irccat.json

@@ -17,7 +17,8 @@
 	    "irccat": "#irccat-dev"
 	}
        }
-    }
+    },
+    "health_endpoint": "/healthz"
   },
   "irc": {
     "server": "irc.example.com:6697",
@@ -30,7 +31,9 @@
     "sasl_login": "",
     "sasl_pass": "",
     "channels": ["#channel"],
-    "keys": {"#channel": "join_key"}
+    "keys": {"#channel": "join_key"},
+    "health_file": "./health.timestamp",
+    "health_period": "5m"
   },
   "commands": {
     "auth_channel": "#channel",

healthcheck/healthcheck.go

@@ -0,0 +1,43 @@
+// Command healthcheck reads a file containing a UNIX UTC timestamp and exits
+// nonzero after printing a message to stderr if the allotted time has elapsed
+// since a value was last recorded. Config value irc.health_period specifies
+// the max allotted time plus a small cushion for lag. It defaults to fifteen
+// minutes, which is go-ircevent's default PING frequency (as of
+// github.com/thoj/go-ircevent@v0.0.0-20210723090443-73e444401d64). Optional
+// config item irc.health_file designates the path to the timestamp file. If
+// unset, the program says so (to stderr) and exits zero.
+package main
+
+import (
+	"log"
+	"time"
+
+	"github.com/irccloud/irccat/util"
+	"github.com/spf13/viper"
+)
+
+var lagInterval = 10 * time.Second // for testing
+var defaultPeriod = 15 * time.Minute
+
+func main() {
+	viper.SetConfigName("irccat")
+	viper.AddConfigPath("/etc")
+	viper.AddConfigPath(".")
+	viper.SetDefault("irc.health_period", defaultPeriod)
+
+	if err := viper.ReadInConfig(); err != nil {
+		log.Fatalln("Error reading config file. Exiting.")
+	}
+
+	healthFile := viper.GetString("irc.health_file")
+	if healthFile == "" {
+		log.Println("Config option irc.health_file unset; exiting.")
+		return
+	}
+
+	freq := lagInterval + viper.GetDuration("irc.health_period")
+
+	if err := util.CheckTimestamp(healthFile, freq); err != nil {
+		log.Fatalln(err.Error())
+	}
+}

httplistener/health.go

@@ -0,0 +1,44 @@
+package httplistener
+
+import (
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/irccloud/irccat/util"
+	"github.com/spf13/viper"
+)
+
+var LagInterval = 10 * time.Second // for testing
+var DefaultPeriod = 15 * time.Minute
+
+// healthHandler returns non-2xx if the configured timeout has elapsed.
+//
+// This mainly exists to present an interface for supervisors relying on
+// liveliness/readiness probes (e.g., for Kubernetes deployments). However, a
+// conservative client could query it before sending a payload. See also
+// /healthcheck in this same pkg.
+func (hl *HTTPListener) healthHandler(
+	w http.ResponseWriter,
+	request *http.Request,
+) {
+	if request.Method != "GET" {
+		http.NotFound(w, request)
+		return
+	}
+	healthFile := viper.GetString("irc.health_file")
+	if healthFile == "" {
+		http.NotFound(w, request)
+		return
+	}
+	viper.SetDefault("irc.health_period", DefaultPeriod)
+
+	freq := LagInterval + viper.GetDuration("irc.health_period")
+	err := util.CheckTimestamp(healthFile, freq)
+	if err != nil {
+		log.Criticalf("%s", err)
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	fmt.Fprintln(w, "OK")
+}

httplistener/health_test.go

@@ -0,0 +1,88 @@
+package httplistener
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"path"
+	"testing"
+	"time"
+
+	"net/http"
+
+	"github.com/irccloud/irccat/util"
+	"github.com/juju/loggo"
+	"github.com/spf13/viper"
+)
+
+var origLag = LagInterval
+
+var configFmt = `---
+irc:
+  health_file: %s
+  health_period: 1ms
+http:
+  health_endpoint: /testing/healthz
+`
+
+func startServer(t *testing.T) {
+	hl := HTTPListener{
+		http: http.Server{Addr: "localhost:18045"},
+	}
+	http.HandleFunc(viper.GetString("http.health_endpoint"), hl.healthHandler)
+	go hl.http.ListenAndServe()
+	t.Cleanup(func() {hl.http.Shutdown(context.Background())})
+}
+
+func getOne(t *testing.T) (*http.Response, string) {
+	res, err := http.Get("http://localhost:18045/testing/healthz")
+	if err != nil {
+		t.Error(err)
+	}
+	got, err := io.ReadAll(res.Body)
+	if err != nil {
+		t.Error(err)
+	}
+	err = res.Body.Close()
+	if err != nil {
+		t.Error(err)
+	}
+	return res, string(got)
+}
+
+func TestHealthHandler(t *testing.T) {
+	writer, err := loggo.RemoveWriter("default")
+	if err != nil {
+		t.Error(err)
+	}
+	t.Cleanup(func() {loggo.DefaultContext().AddWriter("default", writer)})
+	LagInterval = 0
+	t.Cleanup(func() {LagInterval = origLag})
+	dir := t.TempDir()
+	now := time.Now()
+	file := path.Join(dir, "timestamp")
+	if err := util.WriteTimestamp(file, now); err != nil {
+		t.Error(err)
+	}
+	viper.SetConfigType("yaml")
+	config := []byte(fmt.Sprintf(configFmt, file))
+	viper.ReadConfig(bytes.NewBuffer(config))
+	startServer(t)
+	time.Sleep(time.Millisecond)
+	// Fail
+	resp, got := getOne(t)
+	if resp.StatusCode != 500 {
+		t.Error("unexpected status", resp.Status)
+	}
+	t.Log(resp.Status, got)
+	// Success
+	viper.Set("irc.health_period", time.Second)
+	resp, got = getOne(t)
+	if resp.StatusCode != 200 {
+		t.Error("unexpected failure", resp.Status)
+	}
+	if string(got) != "OK\n" {
+		t.Error("unexpected output", string(got))
+	}
+}

httplistener/httplistener.go

@@ -45,6 +45,12 @@ func New(irc *irc.Connection) (*HTTPListener, error) {
 		mux.HandleFunc("/prometheus", hl.prometheusHandler)
 	}
 
+	if viper.IsSet("http.health_endpoint") {
+		ep := viper.GetString("http.health_endpoint")
+		log.Infof("Listening for HTTP GET requests at", ep)
+		mux.HandleFunc(ep, hl.healthHandler)
+	}
+
 	hl.http.Handler = mux
 	if viper.GetBool("http.tls") {
 		go hl.http.ListenAndServeTLS(viper.GetString("http.tls_cert"), viper.GetString("http.tls_key"))

irc.go

@@ -17,6 +17,9 @@ func (i *IRCCat) connectIRC(debug bool) error {
 	irccon.Timeout = time.Second * 15
 	irccon.RequestCaps = []string{"away-notify", "account-notify", "draft/message-tags-0.2"}
 	irccon.UseTLS = viper.GetBool("irc.tls")
+	if viper.IsSet("irc.health_period") {
+		irccon.PingFreq = viper.GetDuration("irc.health_period")
+	}
 
 	if viper.IsSet("irc.sasl_pass") && viper.GetString("irc.sasl_pass") != "" {
 		if viper.IsSet("irc.sasl_login") && viper.GetString("irc.sasl_login") != "" {
@@ -52,6 +55,7 @@ func (i *IRCCat) connectIRC(debug bool) error {
 	irccon.AddCallback("QUIT", i.handleQuit)
 	irccon.AddCallback("KILL", i.handleQuit)
 	irccon.AddCallback("NICK", i.handleNick)
+	irccon.AddCallback("PONG", i.handlePong)
 
 	return nil
 }

main.go

@@ -3,6 +3,8 @@ package main
 import (
 	"flag"
 	"fmt"
+	"time"
+
 	"github.com/deckarep/golang-set"
 	"github.com/fsnotify/fsnotify"
 	"github.com/irccloud/irccat/httplistener"
@@ -13,6 +15,7 @@ import (
 	"os"
 	"os/signal"
 	"syscall"
+	"github.com/irccloud/irccat/util"
 )
 
 var log = loggo.GetLogger("main")
@@ -106,3 +109,16 @@ func (i *IRCCat) handleConfigChange(e fsnotify.Event) {
 		i.channels.Remove(channel)
 	}
 }
+
+// handlePong writes the current time in UNIX seconds to a designated file.
+// Opt in by specifying a file path for config item irc.health_file.
+func (i *IRCCat) handlePong(e *irc.Event) {
+	healthFile := viper.GetString("irc.health_file")
+	if healthFile == "" {
+		return
+	}
+	err:= util.WriteTimestamp(healthFile, time.Now())
+	if err != nil {
+		log.Criticalf("%s", err)
+	}
+}

util/timestamp.go

@@ -0,0 +1,53 @@
+package util
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+)
+
+func isExpired(lastStamp int64, period time.Duration) bool {
+	return time.Now().Sub(time.Unix(lastStamp, 0)) > period
+}
+
+func getTimestamp(tsFile string) (int64, error) {
+	raw, err := os.ReadFile(tsFile)
+	if err != nil {
+		return 0, fmt.Errorf("Couldn't read timestamp file: %s", err)
+	}
+	s := strings.TrimRight(string(raw), "\n")
+	ts, err := strconv.ParseInt(s, 10, 64)
+	if err != nil {
+		// Parsing error already includes offending text
+		return 0, fmt.Errorf("Couldn't parse timestamp: %s", err)
+	}
+	return ts, nil
+}
+
+// WriteTimestamp creates a timestamp file.
+func WriteTimestamp(tsFile string, t time.Time) error {
+	s := fmt.Sprintf("%d\n", t.Unix())
+	err := os.WriteFile(tsFile, []byte(s), 0666)
+	if err != nil {
+		return fmt.Errorf("Couldn't write to timestamp file: %s", err)
+	}
+	return nil
+}
+
+// CheckTimestamp reads a timestamp file and returns an error if it's expired.
+//
+// The file should contain a decimal representation of a Unix timestamp and an
+// optional LF newline.
+func CheckTimestamp(tsFile string, period time.Duration) error {
+	ts, err := getTimestamp(tsFile)
+	if err != nil {
+		return err
+	}
+	if isExpired(ts, period) {
+		diff := time.Now().Sub(time.Unix(ts, 0).Add(period))
+		return fmt.Errorf("Timeout exceeded by %s", diff.String())
+	}
+	return nil
+}

util/timestamp_test.go

@@ -0,0 +1,49 @@
+package util
+
+import (
+	"os"
+	"path"
+	"testing"
+	"time"
+)
+
+func TestIsExpired(t *testing.T) {
+	ts := time.Now().Unix()
+	if isExpired(ts, time.Second) {
+		t.Error("Shouldn't have expired")
+	}
+	if !isExpired(ts, time.Microsecond) {
+		t.Error("Should've expired")
+	}
+}
+
+func TestCheckTimestamp(t *testing.T) {
+	dir := t.TempDir()
+	now := time.Now()
+	file := path.Join(dir, "timestamp")
+	WriteTimestamp(file, now)
+	if err := CheckTimestamp(file, time.Second); err != nil {
+		t.Error(err)
+	}
+	err := CheckTimestamp(file, time.Microsecond)
+	if err == nil {
+		t.Error("Did not raise timeout")
+	}
+	t.Log(err)
+	fake := path.Join(dir, "fake")
+	// File missing
+	err = CheckTimestamp(fake, time.Second)
+	if err == nil {
+		t.Error("Did not raise missing file error")
+	}
+	t.Log(err)
+	// Wrong format
+	if err := os.WriteFile(fake, []byte{':', '('}, 0600); err != nil {
+		t.Error(err)
+	}
+	err = CheckTimestamp(fake, time.Second)
+	if err == nil {
+		t.Error("Did not raise bad parse error")
+	}
+	t.Log(err)
+}