RegisterAgent with hostname

Transfer the agent hostname to the server's model.agent.Name field.

Previously the autoscaler had to create the agent with the server and
get a unique token to pass to the agent at boot up.
This allows to get the right name for the agent while using the shared
master agent token at agent boot up.
Both ways are still supported.

server/grpc/rpc.go

@@ -52,12 +52,8 @@ type RPC struct {
 
 // Next implements the rpc.Next function
 func (s *RPC) Next(c context.Context, agentFilter rpc.Filter) (*rpc.Workflow, error) {
-	metadata, ok := grpcMetadata.FromIncomingContext(c)
-	if ok {
-		hostname, ok := metadata["hostname"]
-		if ok && len(hostname) != 0 {
-			log.Debug().Msgf("agent connected: %s: polling", hostname[0])
-		}
+	if hostname, err := s.getHostnameFromContext(c); err == nil {
+		log.Debug().Msgf("agent connected: %s: polling", hostname)
 	}
 
 	fn, err := createFilterFunc(agentFilter)
@@ -337,6 +333,12 @@ func (s *RPC) RegisterAgent(ctx context.Context, platform, backend, version stri
 		return -1, err
 	}
 
+	if agent.Name == "" {
+		if hostname, err := s.getHostnameFromContext(ctx); err == nil {
+			agent.Name = hostname
+		}
+	}
+
 	agent.Backend = backend
 	agent.Platform = platform
 	agent.Capacity = capacity
@@ -443,3 +445,14 @@ func (s *RPC) getAgentFromContext(ctx context.Context) (*model.Agent, error) {
 
 	return s.store.AgentFind(agentID)
 }
+
+func (s *RPC) getHostnameFromContext(ctx context.Context) (string, error) {
+	metadata, ok := grpcMetadata.FromIncomingContext(ctx)
+	if ok {
+		hostname, ok := metadata["hostname"]
+		if ok && len(hostname) != 0 {
+			return hostname[0], nil
+		}
+	}
+	return "", errors.New("no hostname in metadata")
+}

server/grpc/rpc_test.go

@@ -0,0 +1,108 @@
+// Copyright 2022 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 grpc
+
+import (
+	"context"
+	"testing"
+
+	"github.com/franela/goblin"
+	"github.com/stretchr/testify/assert"
+	"go.woodpecker-ci.org/woodpecker/v2/server/model"
+	mocks_store "go.woodpecker-ci.org/woodpecker/v2/server/store/mocks"
+	"google.golang.org/grpc/metadata"
+)
+
+func TestRegisterAgent(t *testing.T) {
+	g := goblin.Goblin(t)
+	g.Describe("When existing agent Name is empty", func() {
+		g.It("Should update Name with hostname from metadata", func() {
+			store := mocks_store.NewStore(t)
+			storeAgent := new(model.Agent)
+			storeAgent.ID = 1337
+			updatedAgent := model.Agent{
+				ID:          1337,
+				Created:     0,
+				Updated:     0,
+				Name:        "hostname",
+				OwnerID:     0,
+				Token:       "",
+				LastContact: 0,
+				Platform:    "platform",
+				Backend:     "backend",
+				Capacity:    2,
+				Version:     "version",
+				NoSchedule:  false,
+			}
+
+			store.On("AgentFind", int64(1337)).Once().Return(storeAgent, nil)
+			store.On("AgentUpdate", &updatedAgent).Once().Return(nil)
+			rpc := RPC{
+				store: store,
+			}
+			ctx := metadata.NewIncomingContext(
+				context.Background(),
+				metadata.Pairs("hostname", "hostname", "agent_id", "1337"),
+			)
+			capacity := int32(2)
+			agentID, err := rpc.RegisterAgent(ctx, "platform", "backend", "version", capacity)
+			if !assert.NoError(t, err) {
+				t.Fail()
+			}
+
+			assert.EqualValues(t, 1337, agentID)
+		})
+	})
+
+	g.Describe("When existing agent hostname is present", func() {
+		g.It("Should not update the hostname", func() {
+			store := mocks_store.NewStore(t)
+			storeAgent := new(model.Agent)
+			storeAgent.ID = 1337
+			storeAgent.Name = "originalHostname"
+			updatedAgent := model.Agent{
+				ID:          1337,
+				Created:     0,
+				Updated:     0,
+				Name:        "originalHostname",
+				OwnerID:     0,
+				Token:       "",
+				LastContact: 0,
+				Platform:    "platform",
+				Backend:     "backend",
+				Capacity:    2,
+				Version:     "version",
+				NoSchedule:  false,
+			}
+
+			store.On("AgentFind", int64(1337)).Once().Return(storeAgent, nil)
+			store.On("AgentUpdate", &updatedAgent).Once().Return(nil)
+			rpc := RPC{
+				store: store,
+			}
+			ctx := metadata.NewIncomingContext(
+				context.Background(),
+				metadata.Pairs("hostname", "newHostname", "agent_id", "1337"),
+			)
+			capacity := int32(2)
+			agentID, err := rpc.RegisterAgent(ctx, "platform", "backend", "version", capacity)
+			if !assert.NoError(t, err) {
+				t.Fail()
+			}
+
+			assert.EqualValues(t, 1337, agentID)
+		})
+	})
+}