From d893e2489baacd05162ac1d7f6894fb63ec3b6dd Mon Sep 17 00:00:00 2001
From: Gianmaria Del Monte <g.macmount@gmail.com>
Date: Mon, 3 Jul 2023 11:10:52 +0200
Subject: [PATCH] dump config on SIGUSR1

---
 cmd/revad/main.go              |  2 ++
 cmd/revad/pkg/config/config.go |  1 +
 cmd/revad/runtime/runtime.go   | 42 ++++++++++++++++++++++++++++++++--
 3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/cmd/revad/main.go b/cmd/revad/main.go
index 991073ace7a..aad02a6baf7 100644
--- a/cmd/revad/main.go
+++ b/cmd/revad/main.go
@@ -115,6 +115,8 @@ func handleSignalFlag() {
 			signal = syscall.SIGQUIT
 		case "stop":
 			signal = syscall.SIGTERM
+		case "dump":
+			signal = syscall.SIGUSR1
 		default:
 			fmt.Fprintf(os.Stderr, "unknown signal %q\n", *signalFlag)
 			os.Exit(1)
diff --git a/cmd/revad/pkg/config/config.go b/cmd/revad/pkg/config/config.go
index 846b03374e1..732d6d4e7b2 100644
--- a/cmd/revad/pkg/config/config.go
+++ b/cmd/revad/pkg/config/config.go
@@ -59,6 +59,7 @@ type Shared struct {
 // Core holds the core configuration.
 type Core struct {
 	MaxCPUs            string `key:"max_cpus"             mapstructure:"max_cpus"`
+	ConfigDumpFile     string `key:"config_dump_file"     mapstructure:"config_dump_file"     default:"/tmp/reva-dump.toml"`
 	TracingEnabled     bool   `key:"tracing_enabled"      mapstructure:"tracing_enabled"      default:"true"`
 	TracingEndpoint    string `key:"tracing_endpoint"     mapstructure:"tracing_endpoint"     default:"localhost:6831"`
 	TracingCollector   string `key:"tracing_collector"    mapstructure:"tracing_collector"`
diff --git a/cmd/revad/runtime/runtime.go b/cmd/revad/runtime/runtime.go
index 3a4b6011097..e0545a98eee 100644
--- a/cmd/revad/runtime/runtime.go
+++ b/cmd/revad/runtime/runtime.go
@@ -21,10 +21,14 @@ package runtime
 import (
 	"fmt"
 	"net"
+	"os"
+	"os/signal"
 	"runtime"
 	"strconv"
 	"strings"
+	"syscall"
 
+	"github.com/BurntSushi/toml"
 	"github.com/pkg/errors"
 
 	"github.com/cs3org/reva/cmd/revad/pkg/config"
@@ -115,7 +119,7 @@ func New(config *config.Config, opt ...Option) (*Reva, error) {
 		return nil, err
 	}
 
-	return &Reva{
+	r := &Reva{
 		config:     config,
 		servers:    servers,
 		serverless: serverless,
@@ -123,7 +127,41 @@ func New(config *config.Config, opt ...Option) (*Reva, error) {
 		lns:        listeners,
 		pidfile:    opts.PidFile,
 		log:        log,
-	}, nil
+	}
+	r.initConfigDumper()
+	return r, nil
+}
+
+func (r *Reva) initConfigDumper() {
+	// dump the config when the process receives a SIGUSR1 signal
+	sigs := make(chan os.Signal, 1)
+	signal.Notify(sigs, syscall.SIGUSR1)
+
+	go func() {
+		<-sigs
+		r.dumpConfig()
+	}()
+}
+
+func (r *Reva) dumpConfig() {
+	cfg := r.config.Dump()
+	// TODO: merge this config with the one received from
+	// the running services
+	out := r.config.Core.ConfigDumpFile
+	f, err := os.OpenFile(out, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0644)
+	if err != nil {
+		r.log.Error().Err(err).Msgf("error opening file %s for dumping the config", out)
+		return
+	}
+	defer f.Close()
+
+	enc := toml.NewEncoder(f)
+	enc.Indent = ""
+	if err := enc.Encode(cfg); err != nil {
+		r.log.Error().Err(err).Msg("error encoding config")
+		return
+	}
+	r.log.Debug().Msgf("config dumped successfully in %s", out)
 }
 
 func servicesAddresses(cfg *config.Config) map[string]grace.Addressable {