Implements fetcher runner by Cron instead of Config.MinFetchInterval

README.md

@@ -25,7 +25,7 @@ go get github.com/jpillora/overseer
 
 This program works with process managers, supports graceful, zero-down time restarts and self-upgrades its own binary.
 
-``` go
+```go
 package main
 
 import (
@@ -77,11 +77,21 @@ See [Config](https://godoc.org/github.com/jpillora/overseer#Config)uration optio
 
 ### More examples
 
-See the [example/](example/) directory and run `example.sh`, you should see the following output:
+
+See the [example/](example/) directory and run `example.sh EXAMPLE_NAME`, you should see the following output:
 
 ```sh
 $ cd example/
-$ sh example.sh
+```
+
+Examples:
+- default: `$ sh example.sh default` (see above)
+- cron_default: `$ sh example.sh cron_default`
+- cron_custom:  `$ sh example.sh cron_custom`
+
+
+```sh
+$ sh example.sh default
 BUILT APP (1)
 RUNNING APP
 app#1 (031c802ee74f00b2a5c52f2fe647523973c09441) listening...
@@ -148,6 +158,50 @@ func main() {
 }
 ```
 
+#### Using CRON
+
+##### Using default cron instance
+
+```go
+import (
+	"github.com/robfig/cron"
+)
+
+func main() {
+	schedule, _ := cron.Parse("@daily")
+	overseer.Run(overseer.Config{
+		Program: prog,
+		Address: ":3000",
+
+		FetchCronSchedule: &schedule,
+	})
+}
+```
+
+##### Using your cron instance
+
+```go
+import (
+	"github.com/robfig/cron"
+)
+
+func main() {
+	Cron := cron.New()
+	Cron.Start()
+	defer Cron.Stop()
+
+	schedule, _ := cron.Parse("@daily")
+	overseer.Run(overseer.Config{
+		Program: prog,
+		Address: ":3000",
+
+		Cron: Cron,
+		FetchCronSchedule: &schedule,
+	})
+}
+```
+
+
 ### Known issues
 
 * The master process's `overseer.Config` cannot be changed via an upgrade, the master process must be restarted.

example/cron_custom/main.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"github.com/jpillora/overseer"
+	"github.com/jpillora/overseer/example"
+	"github.com/jpillora/overseer/fetcher"
+	"github.com/robfig/cron"
+)
+
+//see example.sh for the use-case
+
+// BuildID is compile-time variable
+var BuildID = "0"
+
+//then create another 'main' which runs the upgrades
+//'main()' is run in the initial process
+func main() {
+	Cron := cron.New()
+	Cron.Start()
+	defer Cron.Stop()
+
+	schedule, _ := cron.Parse("@every 5s")
+
+	overseer.Run(overseer.Config{
+		Program: example.Prog(BuildID),
+		Address: ":5001",
+		Fetcher: &fetcher.File{Path: "my_app_next"},
+		Debug:   false, //display log of overseer actions
+
+		Cron:              Cron,
+		FetchCronSchedule: &schedule,
+	})
+}

example/cron_default/main.go

@@ -0,0 +1,23 @@
+package main
+
+import (
+	"github.com/jpillora/overseer"
+	"github.com/jpillora/overseer/example"
+	"github.com/jpillora/overseer/fetcher"
+)
+
+//see example.sh for the use-case
+
+// BuildID is compile-time variable
+var BuildID = "0"
+
+//then create another 'main' which runs the upgrades
+//'main()' is run in the initial process
+func main() {
+	overseer.Run(overseer.Config{
+		Program: example.Prog(BuildID),
+		Address: ":5001",
+		Fetcher: &fetcher.File{Path: "my_app_next"},
+		Debug:   false, //display log of overseer actions
+	})
+}

example/default/main.go

@@ -0,0 +1,23 @@
+package main
+
+import (
+	"github.com/jpillora/overseer"
+	"github.com/jpillora/overseer/example"
+	"github.com/jpillora/overseer/fetcher"
+)
+
+//see ../example.sh default for the use-case
+
+// BuildID is compile-time variable
+var BuildID = "0"
+
+//then create another 'main' which runs the upgrades
+//'main()' is run in the initial process
+func main() {
+	overseer.Run(overseer.Config{
+		Program: example.Prog(BuildID),
+		Address: ":5001",
+		Fetcher: &fetcher.File{Path: "my_app_next"},
+		Debug:   false, //display log of overseer actions
+	})
+}

example/example.sh

@@ -1,5 +1,12 @@
 #!/bin/bash
 
+if [ "$1" = '' ]; then
+    echo "Usage: $0 EXAMPLE_NAME" >&2
+    exit 1
+fi
+
+cd "$1" || exit $?
+
 #NOTE: DONT CTRL+C OR CLEANUP WONT OCCUR
 #      ENSURE PORTS 5001,5002 ARE UNUSED
 

example/prog.go

@@ -0,0 +1,24 @@
+package example
+
+import (
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/jpillora/overseer"
+)
+
+//convert your 'main()' into a 'prog(state)'
+//'prog()' is run in a child process
+func Prog(BuildID string) func(state overseer.State) {
+	return func(state overseer.State) {
+		fmt.Printf("app#%s (%s) listening...\n", BuildID, state.ID)
+		http.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			d, _ := time.ParseDuration(r.URL.Query().Get("d"))
+			time.Sleep(d)
+			fmt.Fprintf(w, "app#%s (%s) says hello\n", BuildID, state.ID)
+		}))
+		http.Serve(state.Listener, nil)
+		fmt.Printf("app#%s (%s) exiting...\n", BuildID, state.ID)
+	}
+}

overseer.go

@@ -5,6 +5,7 @@ package overseer
 import (
 	"errors"
 	"fmt"
+	"github.com/robfig/cron"
 	"log"
 	"os"
 	"runtime"
@@ -44,6 +45,12 @@ type Config struct {
 	//This helps to prevent unwieldy fetch.Interfaces from hogging
 	//too many resources. Defaults to 1 second.
 	MinFetchInterval time.Duration
+	//FetchCronRule defines the cron (github.com/robfig/cron) rule instead of
+	//MinFetchInterval
+	FetchCronSchedule *cron.Schedule
+	//Cron cron instance for use instead of interval.
+	//See `FetchCronSchedule` and `MinFetchInterval` fields.
+	Cron *cron.Cron
 	//PreUpgrade runs after a binary has been retrieved, user defined checks
 	//can be run here and returning an error will cancel the upgrade.
 	PreUpgrade func(tempBinaryPath string) error

proc_master.go

@@ -19,6 +19,7 @@ import (
 	"time"
 
 	"github.com/kardianos/osext"
+	"github.com/robfig/cron"
 )
 
 var tmpBinPath = filepath.Join(os.TempDir(), "overseer-"+token())
@@ -40,6 +41,8 @@ type master struct {
 	descriptorsReleased chan bool
 	signalledAt         time.Time
 	printCheckUpdate    bool
+	fetchingMux         sync.Mutex
+	fetching            bool
 }
 
 func (mp *master) run() error {
@@ -59,8 +62,17 @@ func (mp *master) run() error {
 	}
 	if mp.Config.Fetcher != nil {
 		mp.printCheckUpdate = true
-		mp.fetch()
-		go mp.fetchLoop()
+		if mp.FetchCronSchedule != nil {
+			if mp.Cron == nil {
+				mp.Cron = cron.New()
+				mp.Cron.Start()
+				defer mp.Cron.Stop()
+			}
+			go mp.Cron.Schedule(*mp.FetchCronSchedule, cron.FuncJob(mp.fetch))
+		} else {
+			mp.fetch()
+			go mp.fetchLoop()
+		}
 	}
 	return mp.forkLoop()
 }
@@ -196,9 +208,17 @@ func (mp *master) fetchLoop() {
 }
 
 func (mp *master) fetch() {
-	if mp.restarting {
+	if mp.fetching || mp.restarting {
 		return //skip if restarting
 	}
+	mp.fetchingMux.Lock()
+	mp.fetching = true
+
+	defer func() {
+		mp.fetching = false
+		mp.fetchingMux.Unlock()
+	}()
+
 	if mp.printCheckUpdate {
 		mp.debugf("checking for updates...")
 	}