From 268c2db394ce5f909230fb150b6c9f3af4cc0fa8 Mon Sep 17 00:00:00 2001
From: qwerty287 <qwerty287@posteo.de>
Date: Wed, 24 Jan 2024 13:53:36 +0100
Subject: [PATCH 1/7] Modularize agent (wip)

---
 cli/exec/exec.go                          | 13 +++--
 cmd/agent/{ => core}/agent.go             | 65 +++++++----------------
 cmd/agent/{ => core}/agent_test.go        |  2 +-
 cmd/agent/{ => core}/config.go            |  2 +-
 cmd/agent/{ => core}/config_test.go       |  2 +-
 cmd/agent/{ => core}/flags.go             |  2 +-
 cmd/agent/{ => core}/health.go            |  2 +-
 cmd/agent/{ => core}/health_test.go       |  2 +-
 cmd/agent/core/run.go                     | 48 +++++++++++++++++
 cmd/agent/docker.go                       |  6 +++
 cmd/agent/kubernetes.go                   |  7 +++
 cmd/agent/local.go                        |  7 +++
 cmd/agent/main.go                         | 31 +----------
 pipeline/backend/backend.go               |  2 +-
 pipeline/backend/docker/docker.go         |  4 ++
 pipeline/backend/kubernetes/kubernetes.go |  4 ++
 pipeline/backend/local/local.go           |  4 ++
 pipeline/backend/types/backend.go         |  5 ++
 18 files changed, 122 insertions(+), 86 deletions(-)
 rename cmd/agent/{ => core}/agent.go (83%)
 rename cmd/agent/{ => core}/agent_test.go (99%)
 rename cmd/agent/{ => core}/config.go (99%)
 rename cmd/agent/{ => core}/config_test.go (99%)
 rename cmd/agent/{ => core}/flags.go (99%)
 rename cmd/agent/{ => core}/health.go (99%)
 rename cmd/agent/{ => core}/health_test.go (99%)
 create mode 100644 cmd/agent/core/run.go
 create mode 100644 cmd/agent/docker.go
 create mode 100644 cmd/agent/kubernetes.go
 create mode 100644 cmd/agent/local.go

diff --git a/cli/exec/exec.go b/cli/exec/exec.go
index 7a28593168..91eb23f33f 100644
--- a/cli/exec/exec.go
+++ b/cli/exec/exec.go
@@ -30,7 +30,6 @@ import (
 
 	"go.woodpecker-ci.org/woodpecker/v2/cli/common"
 	"go.woodpecker-ci.org/woodpecker/v2/pipeline"
-	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend"
 	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/docker"
 	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/kubernetes"
 	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/local"
@@ -213,11 +212,15 @@ func execWithAxis(c *cli.Context, file, repoPath string, axis matrix.Axis) error
 	}
 
 	backendCtx := context.WithValue(c.Context, backendTypes.CliContext, c)
-	backend.Init()
+	backendsByName := map[string]backendTypes.Backend{
+		"docker":              docker.New(),
+		"local":               local.New(),
+		kubernetes.EngineName: kubernetes.New(),
+	}
 
-	backendEngine, err := backend.FindBackend(backendCtx, c.String("backend-engine"))
-	if err != nil {
-		return err
+	backendEngine, ok := backendsByName[c.String("backend-engine")]
+	if !ok {
+		return fmt.Errorf("backend engine '%s' not found", c.String("backend-engine"))
 	}
 
 	if _, err = backendEngine.Load(backendCtx); err != nil {
diff --git a/cmd/agent/agent.go b/cmd/agent/core/agent.go
similarity index 83%
rename from cmd/agent/agent.go
rename to cmd/agent/core/agent.go
index 4ee9ca0074..e42d2eb97d 100644
--- a/cmd/agent/agent.go
+++ b/cmd/agent/core/agent.go
@@ -13,7 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package main
+package core
 
 import (
 	"context"
@@ -39,17 +39,14 @@ import (
 
 	"go.woodpecker-ci.org/woodpecker/v2/agent"
 	agentRpc "go.woodpecker-ci.org/woodpecker/v2/agent/rpc"
-	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend"
 	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/types"
 	"go.woodpecker-ci.org/woodpecker/v2/pipeline/rpc"
-	"go.woodpecker-ci.org/woodpecker/v2/shared/addon"
-	addonTypes "go.woodpecker-ci.org/woodpecker/v2/shared/addon/types"
 	"go.woodpecker-ci.org/woodpecker/v2/shared/logger"
 	"go.woodpecker-ci.org/woodpecker/v2/shared/utils"
 	"go.woodpecker-ci.org/woodpecker/v2/version"
 )
 
-func run(c *cli.Context) error {
+func run(c *cli.Context, backendEngine types.Backend) error {
 	agentConfigPath := c.String("agent-config")
 	hostname := c.String("hostname")
 	if len(hostname) == 0 {
@@ -155,11 +152,6 @@ func run(c *cli.Context) error {
 
 	// new engine
 	backendCtx := context.WithValue(ctx, types.CliContext, c)
-	backendEngine, err := getBackendEngine(backendCtx, c.String("backend-engine"), c.StringSlice("addons"))
-	if err != nil {
-		return err
-	}
-
 	if !backendEngine.IsAvailable(backendCtx) {
 		log.Error().Str("engine", backendEngine.Name()).Msg("selected backend engine is unavailable")
 		return fmt.Errorf("selected backend engine %s is unavailable", backendEngine.Name())
@@ -249,44 +241,27 @@ func run(c *cli.Context) error {
 	return nil
 }
 
-func getBackendEngine(backendCtx context.Context, backendName string, addons []string) (types.Backend, error) {
-	addonBackend, err := addon.Load[types.Backend](addons, addonTypes.TypeBackend)
-	if err != nil {
-		log.Error().Err(err).Msg("cannot load backend addon")
-		return nil, err
-	}
-	if addonBackend != nil {
-		return addonBackend.Value, nil
-	}
-
-	backend.Init()
-	engine, err := backend.FindBackend(backendCtx, backendName)
-	if err != nil {
-		log.Error().Err(err).Msgf("cannot find backend engine '%s'", backendName)
-		return nil, err
-	}
-	return engine, nil
-}
-
-func runWithRetry(context *cli.Context) error {
-	if err := logger.SetupGlobalLogger(context, true); err != nil {
-		return err
-	}
+func runWithRetry(backendEngine types.Backend) func(context *cli.Context) error {
+	return func(context *cli.Context) error {
+		if err := logger.SetupGlobalLogger(context, true); err != nil {
+			return err
+		}
 
-	initHealth()
-
-	retryCount := context.Int("connect-retry-count")
-	retryDelay := context.Duration("connect-retry-delay")
-	var err error
-	for i := 0; i < retryCount; i++ {
-		if err = run(context); status.Code(err) == codes.Unavailable {
-			log.Warn().Err(err).Msg(fmt.Sprintf("cannot connect to server, retrying in %v", retryDelay))
-			time.Sleep(retryDelay)
-		} else {
-			break
+		initHealth()
+
+		retryCount := context.Int("connect-retry-count")
+		retryDelay := context.Duration("connect-retry-delay")
+		var err error
+		for i := 0; i < retryCount; i++ {
+			if err = run(context, backendEngine); status.Code(err) == codes.Unavailable {
+				log.Warn().Err(err).Msg(fmt.Sprintf("cannot connect to server, retrying in %v", retryDelay))
+				time.Sleep(retryDelay)
+			} else {
+				break
+			}
 		}
+		return err
 	}
-	return err
 }
 
 func stringSliceAddToMap(sl []string, m map[string]string) error {
diff --git a/cmd/agent/agent_test.go b/cmd/agent/core/agent_test.go
similarity index 99%
rename from cmd/agent/agent_test.go
rename to cmd/agent/core/agent_test.go
index 1e645e68de..8c3c92db47 100644
--- a/cmd/agent/agent_test.go
+++ b/cmd/agent/core/agent_test.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package main
+package core
 
 import (
 	"testing"
diff --git a/cmd/agent/config.go b/cmd/agent/core/config.go
similarity index 99%
rename from cmd/agent/config.go
rename to cmd/agent/core/config.go
index 61e700e1b0..f2bde30511 100644
--- a/cmd/agent/config.go
+++ b/cmd/agent/core/config.go
@@ -13,7 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package main
+package core
 
 import (
 	"bytes"
diff --git a/cmd/agent/config_test.go b/cmd/agent/core/config_test.go
similarity index 99%
rename from cmd/agent/config_test.go
rename to cmd/agent/core/config_test.go
index fa21ca6b1b..c3c94fd0bc 100644
--- a/cmd/agent/config_test.go
+++ b/cmd/agent/core/config_test.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package main
+package core
 
 import (
 	"os"
diff --git a/cmd/agent/flags.go b/cmd/agent/core/flags.go
similarity index 99%
rename from cmd/agent/flags.go
rename to cmd/agent/core/flags.go
index 0020d3ab0d..bc111d489f 100644
--- a/cmd/agent/flags.go
+++ b/cmd/agent/core/flags.go
@@ -13,7 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package main
+package core
 
 import (
 	"os"
diff --git a/cmd/agent/health.go b/cmd/agent/core/health.go
similarity index 99%
rename from cmd/agent/health.go
rename to cmd/agent/core/health.go
index 8c11589b61..80d5135eaf 100644
--- a/cmd/agent/health.go
+++ b/cmd/agent/core/health.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package main
+package core
 
 import (
 	"encoding/json"
diff --git a/cmd/agent/health_test.go b/cmd/agent/core/health_test.go
similarity index 99%
rename from cmd/agent/health_test.go
rename to cmd/agent/core/health_test.go
index 463928f762..326d37536a 100644
--- a/cmd/agent/health_test.go
+++ b/cmd/agent/core/health_test.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package main
+package core
 
 import (
 	"testing"
diff --git a/cmd/agent/core/run.go b/cmd/agent/core/run.go
new file mode 100644
index 0000000000..b7edd133ad
--- /dev/null
+++ b/cmd/agent/core/run.go
@@ -0,0 +1,48 @@
+// Copyright 2018 Drone.IO Inc.
+//
+// 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 core
+
+import (
+	"os"
+
+	_ "github.com/joho/godotenv/autoload"
+	"github.com/rs/zerolog/log"
+	"github.com/urfave/cli/v2"
+
+	backend "go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/types"
+	"go.woodpecker-ci.org/woodpecker/v2/shared/logger"
+	"go.woodpecker-ci.org/woodpecker/v2/shared/utils"
+	"go.woodpecker-ci.org/woodpecker/v2/version"
+)
+
+func RunAgent(backend backend.Backend) {
+	app := cli.NewApp()
+	app.Name = "woodpecker-agent"
+	app.Version = version.String()
+	app.Usage = "woodpecker agent"
+	app.Action = runWithRetry(backend)
+	app.Commands = []*cli.Command{
+		{
+			Name:   "ping",
+			Usage:  "ping the agent",
+			Action: pinger,
+		},
+	}
+	app.Flags = utils.MergeSlices(flags, logger.GlobalLoggerFlags, backend.Flags())
+
+	if err := app.Run(os.Args); err != nil {
+		log.Fatal().Err(err).Msg("error running agent") //nolint:forbidigo
+	}
+}
diff --git a/cmd/agent/docker.go b/cmd/agent/docker.go
new file mode 100644
index 0000000000..5abc8b6490
--- /dev/null
+++ b/cmd/agent/docker.go
@@ -0,0 +1,6 @@
+//go:build docker
+package main
+
+import "go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/local"
+
+var backend = local.New()
diff --git a/cmd/agent/kubernetes.go b/cmd/agent/kubernetes.go
new file mode 100644
index 0000000000..7ecf64de10
--- /dev/null
+++ b/cmd/agent/kubernetes.go
@@ -0,0 +1,7 @@
+//go:build kubernetes
+
+package main
+
+import "go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/local"
+
+var backend = local.New()
diff --git a/cmd/agent/local.go b/cmd/agent/local.go
new file mode 100644
index 0000000000..9f83a75484
--- /dev/null
+++ b/cmd/agent/local.go
@@ -0,0 +1,7 @@
+//go:build !docker && !kubernetes
+
+package main
+
+import "go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/local"
+
+var backend = local.New()
diff --git a/cmd/agent/main.go b/cmd/agent/main.go
index 01bb60246c..0b3cc77abc 100644
--- a/cmd/agent/main.go
+++ b/cmd/agent/main.go
@@ -15,36 +15,9 @@
 package main
 
 import (
-	"os"
-
-	_ "github.com/joho/godotenv/autoload"
-	"github.com/rs/zerolog/log"
-	"github.com/urfave/cli/v2"
-
-	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/docker"
-	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/kubernetes"
-	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/local"
-	"go.woodpecker-ci.org/woodpecker/v2/shared/logger"
-	"go.woodpecker-ci.org/woodpecker/v2/shared/utils"
-	"go.woodpecker-ci.org/woodpecker/v2/version"
+	"go.woodpecker-ci.org/woodpecker/v2/cmd/agent/core"
 )
 
 func main() {
-	app := cli.NewApp()
-	app.Name = "woodpecker-agent"
-	app.Version = version.String()
-	app.Usage = "woodpecker agent"
-	app.Action = runWithRetry
-	app.Commands = []*cli.Command{
-		{
-			Name:   "ping",
-			Usage:  "ping the agent",
-			Action: pinger,
-		},
-	}
-	app.Flags = utils.MergeSlices(flags, logger.GlobalLoggerFlags, docker.Flags, kubernetes.Flags, local.Flags)
-
-	if err := app.Run(os.Args); err != nil {
-		log.Fatal().Err(err).Msg("error running agent") //nolint:forbidigo
-	}
+	core.RunAgent(backend) // TODO allow compiler option
 }
diff --git a/pipeline/backend/backend.go b/pipeline/backend/backend.go
index 99ecb69134..efe291cee3 100644
--- a/pipeline/backend/backend.go
+++ b/pipeline/backend/backend.go
@@ -29,7 +29,7 @@ var (
 	backends       []types.Backend
 )
 
-func Init() {
+func Init(backends []types.Backend) {
 	backends = []types.Backend{
 		docker.New(),
 		local.New(),
diff --git a/pipeline/backend/docker/docker.go b/pipeline/backend/docker/docker.go
index 2406910627..8a92deea5c 100644
--- a/pipeline/backend/docker/docker.go
+++ b/pipeline/backend/docker/docker.go
@@ -93,6 +93,10 @@ func httpClientOfOpts(dockerCertPath string, verifyTLS bool) *http.Client {
 	}
 }
 
+func (e *docker) Flags() []cli.Flag {
+	return Flags
+}
+
 // Load new client for Docker Backend using environment variables.
 func (e *docker) Load(ctx context.Context) (*backend.BackendInfo, error) {
 	c, ok := ctx.Value(backend.CliContext).(*cli.Context)
diff --git a/pipeline/backend/kubernetes/kubernetes.go b/pipeline/backend/kubernetes/kubernetes.go
index 10c0ec841b..09bd7e9e66 100644
--- a/pipeline/backend/kubernetes/kubernetes.go
+++ b/pipeline/backend/kubernetes/kubernetes.go
@@ -129,6 +129,10 @@ func (e *kube) IsAvailable(context.Context) bool {
 	return len(host) > 0
 }
 
+func (e *kube) Flags() []cli.Flag {
+	return Flags
+}
+
 func (e *kube) Load(ctx context.Context) (*types.BackendInfo, error) {
 	config, err := configFromCliContext(ctx)
 	if err != nil {
diff --git a/pipeline/backend/local/local.go b/pipeline/backend/local/local.go
index aee231c655..cd96b470c0 100644
--- a/pipeline/backend/local/local.go
+++ b/pipeline/backend/local/local.go
@@ -66,6 +66,10 @@ func (e *local) IsAvailable(context.Context) bool {
 	return true
 }
 
+func (e *local) Flags() []cli.Flag {
+	return Flags
+}
+
 func (e *local) Load(ctx context.Context) (*types.BackendInfo, error) {
 	c, ok := ctx.Value(types.CliContext).(*cli.Context)
 	if ok {
diff --git a/pipeline/backend/types/backend.go b/pipeline/backend/types/backend.go
index d6cfd09909..5bb765f5a8 100644
--- a/pipeline/backend/types/backend.go
+++ b/pipeline/backend/types/backend.go
@@ -17,6 +17,8 @@ package types
 import (
 	"context"
 	"io"
+
+	"github.com/urfave/cli/v2"
 )
 
 // Backend defines a container orchestration backend and is used
@@ -28,6 +30,9 @@ type Backend interface {
 	// IsAvailable check if the backend is available.
 	IsAvailable(ctx context.Context) bool
 
+	// Flags return the configuration flags of the backend.
+	Flags() []cli.Flag
+
 	// Load loads the backend engine.
 	Load(ctx context.Context) (*BackendInfo, error)
 

From 5ba8834435e97051ffd8edf690c124daea644ad1 Mon Sep 17 00:00:00 2001
From: qwerty287 <qwerty287@posteo.de>
Date: Sun, 28 Jan 2024 14:13:39 +0100
Subject: [PATCH 2/7] Add multi-backends back

---
 cli/exec/exec.go            | 17 +++++++++--------
 cmd/agent/core/agent.go     | 14 +++++++++++---
 cmd/agent/core/run.go       | 10 +++++++---
 cmd/agent/docker.go         |  6 ------
 cmd/agent/kubernetes.go     |  7 -------
 cmd/agent/local.go          |  7 -------
 cmd/agent/main.go           | 10 +++++++++-
 pipeline/backend/backend.go |  9 ---------
 8 files changed, 36 insertions(+), 44 deletions(-)
 delete mode 100644 cmd/agent/docker.go
 delete mode 100644 cmd/agent/kubernetes.go
 delete mode 100644 cmd/agent/local.go

diff --git a/cli/exec/exec.go b/cli/exec/exec.go
index 91eb23f33f..9fc374a39a 100644
--- a/cli/exec/exec.go
+++ b/cli/exec/exec.go
@@ -30,6 +30,7 @@ import (
 
 	"go.woodpecker-ci.org/woodpecker/v2/cli/common"
 	"go.woodpecker-ci.org/woodpecker/v2/pipeline"
+	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend"
 	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/docker"
 	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/kubernetes"
 	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/local"
@@ -212,15 +213,15 @@ func execWithAxis(c *cli.Context, file, repoPath string, axis matrix.Axis) error
 	}
 
 	backendCtx := context.WithValue(c.Context, backendTypes.CliContext, c)
-	backendsByName := map[string]backendTypes.Backend{
-		"docker":              docker.New(),
-		"local":               local.New(),
-		kubernetes.EngineName: kubernetes.New(),
-	}
+	backend.Init([]backendTypes.Backend{
+		docker.New(),
+		local.New(),
+		kubernetes.New(),
+	})
 
-	backendEngine, ok := backendsByName[c.String("backend-engine")]
-	if !ok {
-		return fmt.Errorf("backend engine '%s' not found", c.String("backend-engine"))
+	backendEngine, err := backend.FindBackend(backendCtx, c.String("backend-engine"))
+	if err != nil {
+		return err
 	}
 
 	if _, err = backendEngine.Load(backendCtx); err != nil {
diff --git a/cmd/agent/core/agent.go b/cmd/agent/core/agent.go
index e42d2eb97d..98fa215160 100644
--- a/cmd/agent/core/agent.go
+++ b/cmd/agent/core/agent.go
@@ -39,6 +39,7 @@ import (
 
 	"go.woodpecker-ci.org/woodpecker/v2/agent"
 	agentRpc "go.woodpecker-ci.org/woodpecker/v2/agent/rpc"
+	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend"
 	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/types"
 	"go.woodpecker-ci.org/woodpecker/v2/pipeline/rpc"
 	"go.woodpecker-ci.org/woodpecker/v2/shared/logger"
@@ -46,7 +47,7 @@ import (
 	"go.woodpecker-ci.org/woodpecker/v2/version"
 )
 
-func run(c *cli.Context, backendEngine types.Backend) error {
+func run(c *cli.Context, backendEngines []types.Backend) error {
 	agentConfigPath := c.String("agent-config")
 	hostname := c.String("hostname")
 	if len(hostname) == 0 {
@@ -152,6 +153,13 @@ func run(c *cli.Context, backendEngine types.Backend) error {
 
 	// new engine
 	backendCtx := context.WithValue(ctx, types.CliContext, c)
+	backend.Init(backendEngines)
+	backendName := c.String("backend-engine")
+	backendEngine, err := backend.FindBackend(backendCtx, backendName)
+	if err != nil {
+		log.Error().Err(err).Msgf("cannot find backend engine '%s'", backendName)
+		return err
+	}
 	if !backendEngine.IsAvailable(backendCtx) {
 		log.Error().Str("engine", backendEngine.Name()).Msg("selected backend engine is unavailable")
 		return fmt.Errorf("selected backend engine %s is unavailable", backendEngine.Name())
@@ -241,7 +249,7 @@ func run(c *cli.Context, backendEngine types.Backend) error {
 	return nil
 }
 
-func runWithRetry(backendEngine types.Backend) func(context *cli.Context) error {
+func runWithRetry(backendEngines []types.Backend) func(context *cli.Context) error {
 	return func(context *cli.Context) error {
 		if err := logger.SetupGlobalLogger(context, true); err != nil {
 			return err
@@ -253,7 +261,7 @@ func runWithRetry(backendEngine types.Backend) func(context *cli.Context) error
 		retryDelay := context.Duration("connect-retry-delay")
 		var err error
 		for i := 0; i < retryCount; i++ {
-			if err = run(context, backendEngine); status.Code(err) == codes.Unavailable {
+			if err = run(context, backendEngines); status.Code(err) == codes.Unavailable {
 				log.Warn().Err(err).Msg(fmt.Sprintf("cannot connect to server, retrying in %v", retryDelay))
 				time.Sleep(retryDelay)
 			} else {
diff --git a/cmd/agent/core/run.go b/cmd/agent/core/run.go
index b7edd133ad..d3541037a9 100644
--- a/cmd/agent/core/run.go
+++ b/cmd/agent/core/run.go
@@ -27,12 +27,12 @@ import (
 	"go.woodpecker-ci.org/woodpecker/v2/version"
 )
 
-func RunAgent(backend backend.Backend) {
+func RunAgent(backends []backend.Backend) {
 	app := cli.NewApp()
 	app.Name = "woodpecker-agent"
 	app.Version = version.String()
 	app.Usage = "woodpecker agent"
-	app.Action = runWithRetry(backend)
+	app.Action = runWithRetry(backends)
 	app.Commands = []*cli.Command{
 		{
 			Name:   "ping",
@@ -40,7 +40,11 @@ func RunAgent(backend backend.Backend) {
 			Action: pinger,
 		},
 	}
-	app.Flags = utils.MergeSlices(flags, logger.GlobalLoggerFlags, backend.Flags())
+	agentFlags := utils.MergeSlices(flags, logger.GlobalLoggerFlags)
+	for _, b := range backends {
+		agentFlags = utils.MergeSlices(agentFlags, b.Flags())
+	}
+	app.Flags = agentFlags
 
 	if err := app.Run(os.Args); err != nil {
 		log.Fatal().Err(err).Msg("error running agent") //nolint:forbidigo
diff --git a/cmd/agent/docker.go b/cmd/agent/docker.go
deleted file mode 100644
index 5abc8b6490..0000000000
--- a/cmd/agent/docker.go
+++ /dev/null
@@ -1,6 +0,0 @@
-//go:build docker
-package main
-
-import "go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/local"
-
-var backend = local.New()
diff --git a/cmd/agent/kubernetes.go b/cmd/agent/kubernetes.go
deleted file mode 100644
index 7ecf64de10..0000000000
--- a/cmd/agent/kubernetes.go
+++ /dev/null
@@ -1,7 +0,0 @@
-//go:build kubernetes
-
-package main
-
-import "go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/local"
-
-var backend = local.New()
diff --git a/cmd/agent/local.go b/cmd/agent/local.go
deleted file mode 100644
index 9f83a75484..0000000000
--- a/cmd/agent/local.go
+++ /dev/null
@@ -1,7 +0,0 @@
-//go:build !docker && !kubernetes
-
-package main
-
-import "go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/local"
-
-var backend = local.New()
diff --git a/cmd/agent/main.go b/cmd/agent/main.go
index 0b3cc77abc..d83ba14007 100644
--- a/cmd/agent/main.go
+++ b/cmd/agent/main.go
@@ -16,8 +16,16 @@ package main
 
 import (
 	"go.woodpecker-ci.org/woodpecker/v2/cmd/agent/core"
+	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/docker"
+	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/kubernetes"
+	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/local"
+	backendTypes "go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/types"
 )
 
 func main() {
-	core.RunAgent(backend) // TODO allow compiler option
+	core.RunAgent([]backendTypes.Backend{
+		docker.New(),
+		local.New(),
+		kubernetes.New(),
+	})
 }
diff --git a/pipeline/backend/backend.go b/pipeline/backend/backend.go
index efe291cee3..16688e9a30 100644
--- a/pipeline/backend/backend.go
+++ b/pipeline/backend/backend.go
@@ -18,9 +18,6 @@ import (
 	"context"
 	"fmt"
 
-	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/docker"
-	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/kubernetes"
-	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/local"
 	"go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/types"
 )
 
@@ -30,12 +27,6 @@ var (
 )
 
 func Init(backends []types.Backend) {
-	backends = []types.Backend{
-		docker.New(),
-		local.New(),
-		kubernetes.New(),
-	}
-
 	backendsByName = make(map[string]types.Backend)
 	for _, engine := range backends {
 		backendsByName[engine.Name()] = engine

From 300f3f3331d3f167ae9b8096d41a29c1438aa538 Mon Sep 17 00:00:00 2001
From: qwerty287 <qwerty287@posteo.de>
Date: Sun, 28 Jan 2024 14:19:11 +0100
Subject: [PATCH 3/7] update docs

---
 cmd/agent/core/flags.go                       |  5 ----
 .../75-addons/00-overview.md                  |  1 -
 .../75-addons/20-creating-addons.md           |  1 -
 .../10-custom-agent-backends.md               | 23 +++++++++++++++++++
 4 files changed, 23 insertions(+), 7 deletions(-)
 create mode 100644 docs/docs/92-development/10-custom-agent-backends.md

diff --git a/cmd/agent/core/flags.go b/cmd/agent/core/flags.go
index bc111d489f..5e92f74be3 100644
--- a/cmd/agent/core/flags.go
+++ b/cmd/agent/core/flags.go
@@ -97,9 +97,4 @@ var flags = []cli.Flag{
 		Usage:   "backend to run pipelines on",
 		Value:   "auto-detect",
 	},
-	&cli.StringSliceFlag{
-		EnvVars: []string{"WOODPECKER_ADDONS"},
-		Name:    "addons",
-		Usage:   "list of addon files",
-	},
 }
diff --git a/docs/docs/30-administration/75-addons/00-overview.md b/docs/docs/30-administration/75-addons/00-overview.md
index 485f9ce84e..31c93e7824 100644
--- a/docs/docs/30-administration/75-addons/00-overview.md
+++ b/docs/docs/30-administration/75-addons/00-overview.md
@@ -13,7 +13,6 @@ To adapt Woodpecker to your needs beyond the [configuration](../10-server-config
 Addons can be used for:
 
 - Forges
-- Agent backends
 - Config services
 - Secret services
 - Environment services
diff --git a/docs/docs/30-administration/75-addons/20-creating-addons.md b/docs/docs/30-administration/75-addons/20-creating-addons.md
index 0fd6d2fe07..abae26587a 100644
--- a/docs/docs/30-administration/75-addons/20-creating-addons.md
+++ b/docs/docs/30-administration/75-addons/20-creating-addons.md
@@ -22,7 +22,6 @@ Directly import Woodpecker's Go package (`go.woodpecker-ci.org/woodpecker/woodpe
 | Addon type           | Return type                                                                      |
 | -------------------- | -------------------------------------------------------------------------------- |
 | `Forge`              | `"go.woodpecker-ci.org/woodpecker/woodpecker/v2/server/forge".Forge`             |
-| `Backend`            | `"go.woodpecker-ci.org/woodpecker/woodpecker/v2/pipeline/backend/types".Backend` |
 | `ConfigService`      | `"go.woodpecker-ci.org/woodpecker/v2/server/plugins/config".Extension`           |
 | `SecretService`      | `"go.woodpecker-ci.org/woodpecker/v2/server/model".SecretService`                |
 | `EnvironmentService` | `"go.woodpecker-ci.org/woodpecker/v2/server/model".EnvironmentService`           |
diff --git a/docs/docs/92-development/10-custom-agent-backends.md b/docs/docs/92-development/10-custom-agent-backends.md
new file mode 100644
index 0000000000..dc1fd9d93d
--- /dev/null
+++ b/docs/docs/92-development/10-custom-agent-backends.md
@@ -0,0 +1,23 @@
+# Custom agent backends
+
+If none of our backends fits your usecases, you can write your own.
+
+Therefore, implement the interface `"go.woodpecker-ci.org/woodpecker/woodpecker/v2/pipeline/backend/types".Backend` and
+build a custom agent using your backend with this `main.go`:
+
+```go
+package main
+
+import (
+	"go.woodpecker-ci.org/woodpecker/v2/cmd/agent/core"
+	backendTypes "go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/types"
+)
+
+func main() {
+	core.RunAgent([]backendTypes.Backend{
+		yourBackend,
+	})
+}
+```
+
+It is also possible to use multiple backends, you can select with [`WOODPECKER_BACKEND`](../30-administration/15-agent-config.md#woodpecker_backend) between them.

From ded2577785d9dd89f5e98df2eaa5f0234f18126e Mon Sep 17 00:00:00 2001
From: qwerty287 <qwerty287@posteo.de>
Date: Sun, 28 Jan 2024 14:21:36 +0100
Subject: [PATCH 4/7] fix docs + copyright

---
 cmd/agent/core/run.go                          | 2 +-
 docs/docs/30-administration/15-agent-config.md | 6 ------
 shared/addon/types/types.go                    | 1 -
 3 files changed, 1 insertion(+), 8 deletions(-)

diff --git a/cmd/agent/core/run.go b/cmd/agent/core/run.go
index d3541037a9..90c3656eb7 100644
--- a/cmd/agent/core/run.go
+++ b/cmd/agent/core/run.go
@@ -1,4 +1,4 @@
-// Copyright 2018 Drone.IO Inc.
+// 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.
diff --git a/docs/docs/30-administration/15-agent-config.md b/docs/docs/30-administration/15-agent-config.md
index 26005eaf5a..31a37ab1c7 100644
--- a/docs/docs/30-administration/15-agent-config.md
+++ b/docs/docs/30-administration/15-agent-config.md
@@ -168,12 +168,6 @@ Configures if the gRPC server certificate should be verified, only valid when `W
 
 Configures the backend engine to run pipelines on. Possible values are `auto-detect`, `docker`, `local` or `kubernetes`.
 
-### `WOODPECKER_ADDONS`
-
-> Default: empty
-
-List of addon files. See [addons](./75-addons/00-overview.md).
-
 ### `WOODPECKER_BACKEND_DOCKER_*`
 
 See [Docker backend configuration](./22-backends/10-docker.md#configuration)
diff --git a/shared/addon/types/types.go b/shared/addon/types/types.go
index 158df423b1..3287efc575 100644
--- a/shared/addon/types/types.go
+++ b/shared/addon/types/types.go
@@ -4,7 +4,6 @@ type Type string
 
 const (
 	TypeForge              Type = "forge"
-	TypeBackend            Type = "backend"
 	TypeConfigService      Type = "config_service"
 	TypeSecretService      Type = "secret_service"
 	TypeEnvironmentService Type = "environment_service"

From 41d2a9b26540e9d27578a36d67a00b465a35dad7 Mon Sep 17 00:00:00 2001
From: qwerty287 <qwerty287@posteo.de>
Date: Sun, 28 Jan 2024 14:23:33 +0100
Subject: [PATCH 5/7] fix mdlint

---
 docs/docs/92-development/10-custom-agent-backends.md | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/docs/docs/92-development/10-custom-agent-backends.md b/docs/docs/92-development/10-custom-agent-backends.md
index dc1fd9d93d..3514e73d9e 100644
--- a/docs/docs/92-development/10-custom-agent-backends.md
+++ b/docs/docs/92-development/10-custom-agent-backends.md
@@ -9,14 +9,14 @@ build a custom agent using your backend with this `main.go`:
 package main
 
 import (
-	"go.woodpecker-ci.org/woodpecker/v2/cmd/agent/core"
-	backendTypes "go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/types"
+  "go.woodpecker-ci.org/woodpecker/v2/cmd/agent/core"
+  backendTypes "go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/types"
 )
 
 func main() {
-	core.RunAgent([]backendTypes.Backend{
-		yourBackend,
-	})
+  core.RunAgent([]backendTypes.Backend{
+    yourBackend,
+  })
 }
 ```
 

From 844facb94ef98205c5416c3f755765464d772638 Mon Sep 17 00:00:00 2001
From: qwerty287 <qwerty287@posteo.de>
Date: Sun, 28 Jan 2024 14:30:06 +0100
Subject: [PATCH 6/7] prettier

---
 .../75-addons/20-creating-addons.md                | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/docs/docs/30-administration/75-addons/20-creating-addons.md b/docs/docs/30-administration/75-addons/20-creating-addons.md
index abae26587a..8ad4fe3e9e 100644
--- a/docs/docs/30-administration/75-addons/20-creating-addons.md
+++ b/docs/docs/30-administration/75-addons/20-creating-addons.md
@@ -19,13 +19,13 @@ Directly import Woodpecker's Go package (`go.woodpecker-ci.org/woodpecker/woodpe
 
 ### Return types
 
-| Addon type           | Return type                                                                      |
-| -------------------- | -------------------------------------------------------------------------------- |
-| `Forge`              | `"go.woodpecker-ci.org/woodpecker/woodpecker/v2/server/forge".Forge`             |
-| `ConfigService`      | `"go.woodpecker-ci.org/woodpecker/v2/server/plugins/config".Extension`           |
-| `SecretService`      | `"go.woodpecker-ci.org/woodpecker/v2/server/model".SecretService`                |
-| `EnvironmentService` | `"go.woodpecker-ci.org/woodpecker/v2/server/model".EnvironmentService`           |
-| `RegistryService`    | `"go.woodpecker-ci.org/woodpecker/v2/server/model".RegistryService`              |
+| Addon type           | Return type                                                            |
+| -------------------- | ---------------------------------------------------------------------- |
+| `Forge`              | `"go.woodpecker-ci.org/woodpecker/woodpecker/v2/server/forge".Forge`   |
+| `ConfigService`      | `"go.woodpecker-ci.org/woodpecker/v2/server/plugins/config".Extension` |
+| `SecretService`      | `"go.woodpecker-ci.org/woodpecker/v2/server/model".SecretService`      |
+| `EnvironmentService` | `"go.woodpecker-ci.org/woodpecker/v2/server/model".EnvironmentService` |
+| `RegistryService`    | `"go.woodpecker-ci.org/woodpecker/v2/server/model".RegistryService`    |
 
 ### Using configurations
 

From 9e403114337051f2de99d6c6c27f61cbb915bac4 Mon Sep 17 00:00:00 2001
From: qwerty287 <80460567+qwerty287@users.noreply.github.com>
Date: Sun, 28 Jan 2024 14:40:58 +0100
Subject: [PATCH 7/7] Update run.go

---
 cmd/agent/core/run.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/cmd/agent/core/run.go b/cmd/agent/core/run.go
index 90c3656eb7..b485f5019c 100644
--- a/cmd/agent/core/run.go
+++ b/cmd/agent/core/run.go
@@ -17,6 +17,7 @@ package core
 import (
 	"os"
 
+	// Load config from .env
 	_ "github.com/joho/godotenv/autoload"
 	"github.com/rs/zerolog/log"
 	"github.com/urfave/cli/v2"