Run as cache server (#275)

This PR
- adds the `cache-server` command so act_runner can run as a cache server. When running as a cache server, act_runner only processes the requests related to cache and does not run jobs.
- adds the `external_server` configuration for cache. If specified, act_runner will use this URL as the ACTIONS_CACHE_URL instead of starting a cache server itself.

Reviewed-on: https://gitea.com/gitea/act_runner/pulls/275
Co-authored-by: Zettat123 <zettat123@gmail.com>
Co-committed-by: Zettat123 <zettat123@gmail.com>

internal/app/cmd/cache-server.go

@@ -0,0 +1,69 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/signal"
+
+	"gitea.com/gitea/act_runner/internal/pkg/config"
+
+	"github.com/nektos/act/pkg/artifactcache"
+	log "github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+)
+
+type cacheServerArgs struct {
+	Dir  string
+	Host string
+	Port uint16
+}
+
+func runCacheServer(ctx context.Context, configFile *string, cacheArgs *cacheServerArgs) func(cmd *cobra.Command, args []string) error {
+	return func(cmd *cobra.Command, args []string) error {
+		cfg, err := config.LoadDefault(*configFile)
+		if err != nil {
+			return fmt.Errorf("invalid configuration: %w", err)
+		}
+
+		initLogging(cfg)
+
+		var (
+			dir  = cfg.Cache.Dir
+			host = cfg.Cache.Host
+			port = cfg.Cache.Port
+		)
+
+		// cacheArgs has higher priority
+		if cacheArgs.Dir != "" {
+			dir = cacheArgs.Dir
+		}
+		if cacheArgs.Host != "" {
+			host = cacheArgs.Host
+		}
+		if cacheArgs.Port != 0 {
+			port = cacheArgs.Port
+		}
+
+		cacheHandler, err := artifactcache.StartHandler(
+			dir,
+			host,
+			port,
+			log.StandardLogger().WithField("module", "cache_request"),
+		)
+		if err != nil {
+			return err
+		}
+
+		log.Infof("cache server is listening on %v", cacheHandler.ExternalURL())
+
+		c := make(chan os.Signal, 1)
+		signal.Notify(c, os.Interrupt)
+		<-c
+
+		return nil
+	}
+}

internal/app/cmd/cmd.go

@@ -63,6 +63,19 @@ func Execute(ctx context.Context) {
 		},
 	})
 
+	// ./act_runner cache-server
+	var cacheArgs cacheServerArgs
+	cacheCmd := &cobra.Command{
+		Use:   "cache-server",
+		Short: "Start a cache server for the cache action",
+		Args:  cobra.MaximumNArgs(0),
+		RunE:  runCacheServer(ctx, &configFile, &cacheArgs),
+	}
+	cacheCmd.Flags().StringVarP(&cacheArgs.Dir, "dir", "d", "", "Cache directory")
+	cacheCmd.Flags().StringVarP(&cacheArgs.Host, "host", "s", "", "Host of the cache server")
+	cacheCmd.Flags().Uint16VarP(&cacheArgs.Port, "port", "p", 0, "Port of the cache server")
+	rootCmd.AddCommand(cacheCmd)
+
 	// hide completion command
 	rootCmd.CompletionOptions.HiddenDefaultCmd = true
 

internal/app/run/runner.go

@@ -53,6 +53,9 @@ func NewRunner(cfg *config.Config, reg *config.Registration, cli client.Client)
 		envs[k] = v
 	}
 	if cfg.Cache.Enabled == nil || *cfg.Cache.Enabled {
+		if cfg.Cache.ExternalServer != "" {
+			envs["ACTIONS_CACHE_URL"] = cfg.Cache.ExternalServer
+		} else {
 			cacheHandler, err := artifactcache.StartHandler(
 				cfg.Cache.Dir,
 				cfg.Cache.Host,
@@ -66,6 +69,7 @@ func NewRunner(cfg *config.Config, reg *config.Registration, cli client.Client)
 				envs["ACTIONS_CACHE_URL"] = cacheHandler.ExternalURL() + "/"
 			}
 		}
+	}
 
 	// set artifact gitea api
 	artifactGiteaAPI := strings.TrimSuffix(cli.Address(), "/") + "/api/actions_pipeline/"

internal/pkg/config/config.example.yaml

@@ -45,6 +45,10 @@ cache:
   # The port of the cache server.
   # 0 means to use a random available port.
   port: 0
+  # The external cache server URL. Valid only when enable is true.
+  # If it's specified, act_runner will use this URL as the ACTIONS_CACHE_URL rather than start a server by itself.
+  # The URL should generally end with "/".
+  external_server: ""
 
 container:
   # Specifies the network to which the container will connect.

internal/pkg/config/config.go

@@ -38,6 +38,7 @@ type Cache struct {
 	Dir            string `yaml:"dir"`             // Dir specifies the directory path for caching.
 	Host           string `yaml:"host"`            // Host specifies the caching host.
 	Port           uint16 `yaml:"port"`            // Port specifies the caching port.
+	ExternalServer string `yaml:"external_server"` // ExternalServer specifies the URL of external cache server
 }
 
 // Container represents the configuration for the container.