Improve Docker setup

- Add better explanation on how to run the signaling server yourself.
- Improve temporary postgres setup

Author: erikdubbelboer

README.md

@@ -122,9 +122,21 @@ UDP Transport
 
 While Poki provides hosted STUN/TURN and signaling services for free, you can also self-host these components:
 
-1. Set up your own signaling server using the provided Docker image
-2. Configure your own STUN/TURN servers
-3. Initialize the network with custom endpoints:
+1. Set up your own signaling server
+
+    Using the provided Docker image:
+    ```sh
+    $ docker build -t netlib .
+    $ docker run --rm -v /var/run/docker.sock:/var/run/docker.sock -p 8080:8080 -e ENV=local netlib
+    ```
+    Or by running the signaling server binary directly:
+    ```sh
+    $ go build -o signaling cmd/signaling/main.go
+    $ ENV=local ./signaling
+    ```
+2. For persistent storage remove `ENV=local` and set `DATABASE_URL` to your PostgreSQL database URL.
+3. Configure your own STUN/TURN servers.
+4. Initialize the network with custom endpoints:
 ```js
 const network = new Network('<game-id>', {
   signalingServer: 'wss://your-server.com',

cmd/signaling/main.go

@@ -18,6 +18,7 @@ import (
 	"github.com/poki/netlib/internal/util"
 	"github.com/rs/cors"
 	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
 )
 
 func main() {
@@ -32,7 +33,9 @@ func main() {
 
 	store, flushed, err := stores.FromEnv(ctx)
 	if err != nil {
-		logger.Panic("failed setup store", zap.Error(err))
+		// Don't print a stacktrace here, it's confusing for users.
+		logger.WithOptions(zap.AddStacktrace(zapcore.InvalidLevel)).Error("failed to setup store", zap.Error(err))
+		return
 	}
 
 	if os.Getenv("ENV") == "local" || os.Getenv("ENV") == "test" {

internal/signaling/stores/postgres.go

@@ -624,10 +624,7 @@ func (s *PostgresStore) DoLeaderElection(ctx context.Context, gameID, lobbyCode
 		return nil, err
 	}
 
-	needNewLeader := false
-	if currentLeader == "" {
-		needNewLeader = true
-	}
+	needNewLeader := currentLeader == ""
 
 	if !needNewLeader {
 		found := slices.Contains(peers, currentLeader)

internal/signaling/stores/setup.go

@@ -1,9 +1,12 @@
 package stores
 
 import (
+	"bytes"
 	"context"
 	"fmt"
+	"net"
 	"os"
+	"strings"
 	"time"
 
 	"github.com/jackc/pgx/v5/pgxpool"
@@ -31,7 +34,7 @@ func FromEnv(ctx context.Context) (Store, chan struct{}, error) {
 		}
 		return store, nil, nil
 
-	} else if _, hasDocker := os.LookupEnv("DOCKER_HOST"); hasDocker {
+	} else if os.Getenv("ENV") == "local" || os.Getenv("ENV") == "test" {
 		pool, err := dockertest.NewPool("")
 		if err != nil {
 			return nil, nil, err
@@ -66,7 +69,17 @@ func FromEnv(ctx context.Context) (Store, chan struct{}, error) {
 				return nil, nil, err
 			}
 		}
-		databaseUrl := fmt.Sprintf("postgres://test:test@%s/test?sslmode=disable", resource.GetHostPort("5432/tcp"))
+
+		hostPort := resource.GetHostPort("5432/tcp")
+
+		// If we are running in Docker, we need to replace localhost with host.docker.internal.
+		// This allows us to connect to the postgres dockertest just started inside our container.
+		// localhost will not work in this case as it refers to the container itself.
+		if runningInDocker() {
+			hostPort = strings.ReplaceAll(hostPort, "localhost", "host.docker.internal")
+		}
+
+		databaseUrl := fmt.Sprintf("postgres://test:test@%s/test?sslmode=disable", hostPort)
 
 		// This log message is used by the test suite to pass the database URL to the testproxy.
 		logger.Info("using database", zap.String("url", databaseUrl))
@@ -95,5 +108,21 @@ func FromEnv(ctx context.Context) (Store, chan struct{}, error) {
 		}
 		return store, flushed, nil
 	}
-	return nil, nil, fmt.Errorf("no database configured export DATABASE_URL or DOCKER_HOST to run locally")
+	return nil, nil, fmt.Errorf("no database configured, set DATABASE_URL in production, or ENV=local to automatically start a temporary database")
+}
+
+// runningInDocker returns true if the code is running inside a Docker container.
+func runningInDocker() bool {
+	if _, err := os.Stat("/.dockerenv"); err == nil {
+		return true
+	}
+
+	if b, err := os.ReadFile("/proc/1/cgroup"); err == nil {
+		return bytes.Contains(b, []byte("docker")) ||
+			bytes.Contains(b, []byte("kubepods")) ||
+			bytes.Contains(b, []byte("containerd"))
+	}
+
+	_, err := net.LookupHost("host.docker.internal")
+	return err == nil
 }