Dump config on SIGUSR1 (#4031)

changelog/unreleased/dump-config.md

@@ -0,0 +1,7 @@
+Enhancement: Dump reva config on SIGUSR1
+
+Add an option to the runtime to dump the configuration on a file
+(default to `/tmp/reva-dump.toml` and configurable) when the process
+receives a SIGUSR1 signal. Eventual errors are logged in the log.
+
+https://github.com/cs3org/reva/pull/4031

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)

cmd/revad/pkg/config/config.go

@@ -21,6 +21,8 @@ package config
 import (
 	"fmt"
 	"io"
+	"os"
+	"path/filepath"
 	"reflect"
 
 	"github.com/BurntSushi/toml"
@@ -59,6 +61,7 @@ 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"`
 	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"`
@@ -78,12 +81,19 @@ type Lookuper interface {
 	Lookup(key string) (any, error)
 }
 
+func (c *Config) init() {
+	if c.Core.ConfigDumpFile == "" {
+		c.Core.ConfigDumpFile = filepath.Join(os.TempDir(), "reva-dump.toml")
+	}
+}
+
 // Load loads the configuration from the reader.
 func Load(r io.Reader) (*Config, error) {
 	var c Config
 	if err := defaults.Set(&c); err != nil {
 		return nil, err
 	}
+	c.init()
 	var raw map[string]any
 	if _, err := toml.NewDecoder(r).Decode(&raw); err != nil {
 		return nil, errors.Wrap(err, "config: error decoding toml data")

cmd/revad/pkg/config/config_test.go

@@ -248,6 +248,7 @@ nats_token = "secret-token-example"`
 		MaxCPUs:         "1",
 		TracingEnabled:  true,
 		TracingEndpoint: "localhost:6831",
+		ConfigDumpFile:  "/tmp/reva-dump.toml",
 	}, c2.Core)
 
 	assert.Equal(t, Vars{
@@ -500,6 +501,7 @@ func TestDump(t *testing.T) {
 			"tracing_collector":    "",
 			"tracing_service_name": "",
 			"tracing_service":      "",
+			"config_dump_file":     "",
 		},
 		"vars": map[string]any{
 			"db_username": "root",

cmd/revad/runtime/runtime.go

@@ -22,10 +22,14 @@ import (
 	"context"
 	"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"
@@ -121,7 +125,7 @@ func New(config *config.Config, opt ...Option) (*Reva, error) {
 		return nil, err
 	}
 
-	return &Reva{
+	r := &Reva{
 		ctx:        ctx,
 		config:     config,
 		servers:    servers,
@@ -130,7 +134,40 @@ 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() {
+		for {
+			<-sigs
+			r.dumpConfig()
+		}
+	}()
+}
+
+func (r *Reva) dumpConfig() {
+	cfg := r.config.Dump()
+	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)
+	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 {