fix(agent): persist agent ID after auth to prevent crashloop duplicates

agent/rpc/auth_client_grpc.go

@@ -41,6 +41,10 @@ func NewAuthGrpcClient(conn *grpc.ClientConn, agentToken string, agentID int64)
 	return client
 }
 
+func (c *AuthClient) AgentID() int64 {
+	return c.agentID
+}
+
 func (c *AuthClient) Auth(ctx context.Context) (string, int64, error) {
 	ctx, cancel := context.WithTimeout(ctx, authClientTimeout)
 	defer cancel()

agent/rpc/auth_client_grpc_test.go

@@ -0,0 +1,32 @@
+// Copyright 2024 Woodpecker Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package rpc
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+)
+
+func TestAuthClientAgentID(t *testing.T) {
+	conn, err := grpc.NewClient("localhost:0", grpc.WithTransportCredentials(insecure.NewCredentials()))
+	assert.NoError(t, err)
+	defer conn.Close()
+
+	client := NewAuthGrpcClient(conn, "test-token", 42)
+	assert.Equal(t, int64(42), client.AgentID())
+}

cmd/agent/core/agent.go

@@ -137,6 +137,15 @@ func run(ctx context.Context, c *cli.Command, backends []types.Backend) error {
 		return fmt.Errorf("agent could not auth: %w", err)
 	}
 
+	// Persist the agent ID received during auth so that crashloops reuse the
+	// same server-side entry instead of creating a new one on every restart.
+	if agentConfigPath != "" {
+		agentConfig.AgentID = authClient.AgentID()
+		if err := writeAgentConfig(agentConfig, agentConfigPath); err == nil {
+			log.Debug().Msgf("persisted agent ID %d after auth", agentConfig.AgentID)
+		}
+	}
+
 	conn, err := grpc.NewClient(
 		c.String("server"),
 		transport,