diff --git a/README.md b/README.md
index 37af5bc919c8e254e01022c3cab8a9c247b0c236..88e7f3b5996933a58542610a3cc48d39394a81f0 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,38 @@
# GitLab Runner Droplet Monitor [](https://git.ethitter.com/debian/gitlab-runner-do-monitor/commits/master)
-Monitor Digital Ocean for stale droplets created by GitLab Runner
\ No newline at end of file
+Monitor Digital Ocean for stale droplets created by GitLab Runner
+
+## Configuration
+
+```json
+{
+ "log-dest": "os.Stdout",
+ "api-key": "",
+ "threshold": 5400,
+ "delete-stale": true
+}
+
+```
+
+* `log-dest`: set to a path to write to a log file, otherwise `os.Stdout`
+* `api-key`: Digital Ocean Personal Access Token
+* `threshold`: time, in seconds, after which to consider a runner stale
+* `delete-stale`: whether to delete stale runners, in addition to reporting them
+
+##### A note about `threshold`
+
+This value needs to be greater than the job timeout specified in your GitLab Runner configuration, otherwise a runner may erroneously be considered stale.
+
+## Installation
+
+1. Download the appropriate binary from [tagged releases](https://git.ethitter.com/debian/gitlab-runner-do-monitor/tags), or build the binary yourself.
+1. Copy `config-sample.json` to an appropriate location and update the default values as needed.
+1. Create a cron task to periodically run the monitor.
+
+## Usage
+
+```bash
+./glrdomon -config config.json
+```
+
+* `-config`: specify path to config file, otherwise assumes `./config.json` relative to the binary
diff --git a/config-sample.json b/config-sample.json
new file mode 100644
index 0000000000000000000000000000000000000000..03c7e6a5ae06e67f8dae46fb41a58fb6a4ba1122
--- /dev/null
+++ b/config-sample.json
@@ -0,0 +1,6 @@
+{
+ "log-dest": "os.Stdout",
+ "api-key": "",
+ "threshold": 3600,
+ "delete-stale": true
+}
diff --git a/glrdomon.go b/glrdomon.go
index 79058077776c2ae70a619e5eef9ae972247a4576..262df5fd2ab68f89e7fbf10778b4f9c6f63aa024 100644
--- a/glrdomon.go
+++ b/glrdomon.go
@@ -1,5 +1,239 @@
package main
+import (
+ "context"
+ "encoding/json"
+ "flag"
+ "io/ioutil"
+ "log"
+ "os"
+ "path/filepath"
+ "sync"
+ "time"
+
+ "github.com/digitalocean/godo"
+ "github.com/dustin/go-humanize"
+ "golang.org/x/oauth2"
+)
+
+type config struct {
+ LogDest string `json:"log-dest"`
+ APIKey string `json:"api-key"`
+ Threshold int `json:"threshold"`
+ DeleteStale bool `json:"delete-stale"`
+}
+
+type tokenSource struct {
+ AccessToken string
+}
+
+var (
+ configPath string
+
+ logger *log.Logger
+ logDest string
+
+ apiKey string
+ threshold int
+ deleteStale bool
+
+ wg sync.WaitGroup
+
+ client *godo.Client
+)
+
+func init() {
+ flag.StringVar(&configPath, "config", "./config.json", "Path to configuration file")
+ flag.Parse()
+
+ if !validatePath(&configPath) {
+ usage()
+ }
+
+ configFile, err := ioutil.ReadFile(configPath)
+ if err != nil {
+ usage()
+ }
+
+ cfg := config{}
+ if err = json.Unmarshal(configFile, &cfg); err != nil {
+ usage()
+ }
+
+ apiKey = cfg.APIKey
+ threshold = cfg.Threshold
+ deleteStale = cfg.DeleteStale
+
+ logDest = cfg.LogDest
+ setUpLogger()
+
+ logger.Printf("Starting GitLab Runner monitoring with config %s", configPath)
+
+ if deleteStale {
+ logger.Println("Stale droplets WILL BE DELETED automatically")
+ } else {
+ logger.Println("Stale droplets will be logged, but not deleted")
+ }
+}
+
func main() {
+ authenticate()
+ checkAPI()
+
+ wg.Wait()
+ logger.Println("Execution complete!")
+}
+
+func authenticate() {
+ tokenSource := &tokenSource{
+ AccessToken: apiKey,
+ }
+
+ oauthClient := oauth2.NewClient(context.Background(), tokenSource)
+ client = godo.NewClient(oauthClient)
+}
+
+// oAuth token
+func (t *tokenSource) Token() (*oauth2.Token, error) {
+ token := &oauth2.Token{
+ AccessToken: t.AccessToken,
+ }
+
+ return token, nil
+}
+
+func checkAPI() {
+ ctx := context.TODO()
+ droplets, err := listDroplets(ctx, client)
+ if err != nil {
+ logger.Println("Warning! Failed to retrieve droplet list.")
+ logger.Print(err)
+ return
+ }
+
+ for _, droplet := range droplets {
+ wg.Add(1)
+ go checkDroplet(droplet)
+ }
+}
+
+func listDroplets(ctx context.Context, client *godo.Client) ([]godo.Droplet, error) {
+ list := []godo.Droplet{}
+
+ opt := &godo.ListOptions{}
+ for {
+ droplets, resp, err := client.Droplets.List(ctx, opt)
+ if err != nil {
+ return nil, err
+ }
+
+ for _, d := range droplets {
+ list = append(list, d)
+ }
+
+ if resp.Links == nil || resp.Links.IsLastPage() {
+ break
+ }
+
+ page, err := resp.Links.CurrentPage()
+ if err != nil {
+ return nil, err
+ }
+
+ opt.Page = page + 1
+ }
+
+ return list, nil
+}
+
+func checkDroplet(droplet godo.Droplet) {
+ defer wg.Done()
+
+ if !checkDropletAge(droplet) {
+ return
+ }
+
+ deleted := deleteDroplet(droplet)
+ if deleteStale {
+ if deleted {
+ logger.Printf("Removed droplet %s (%d)", droplet.Name, droplet.ID)
+ } else {
+ logger.Printf("Failed to delete droplet %s (%d)", droplet.Name, droplet.ID)
+ }
+ }
+}
+
+func checkDropletAge(droplet godo.Droplet) bool {
+ thr := time.Now().Add(time.Duration(-threshold) * time.Second)
+ created, err := time.Parse(time.RFC3339, droplet.Created)
+ if err != nil {
+ logger.Printf("Could not parse created-timestamp for droplet ID %d", droplet.ID)
+ return false
+ }
+
+ stale := thr.After(created)
+
+ if stale {
+ logger.Printf("Stale droplet => ID: %d; name: \"%s\"; created: %s, %s (%d)", droplet.ID, droplet.Name, humanize.Time(created), droplet.Created, created.Unix())
+ }
+
+ return stale
+}
+
+func deleteDroplet(droplet godo.Droplet) bool {
+ if !deleteStale {
+ return false
+ }
+
+ logger.Printf("Deleting droplet %s (%d)", droplet.Name, droplet.ID)
+
+ ctx := context.TODO()
+ _, err := client.Droplets.Delete(ctx, droplet.ID)
+
+ return err == nil
+}
+
+func setUpLogger() {
+ logOpts := log.Ldate | log.Ltime | log.LUTC | log.Lshortfile
+
+ if logDest == "os.Stdout" {
+ logger = log.New(os.Stdout, "DEBUG: ", logOpts)
+ } else {
+ path, err := filepath.Abs(logDest)
+ if err != nil {
+ logger.Fatal(err)
+ }
+
+ logFile, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0644)
+ if err != nil {
+ log.Fatal(err)
+ }
+
+ logger = log.New(logFile, "", logOpts)
+ }
+}
+
+func validatePath(path *string) bool {
+ if len(*path) <= 1 {
+ return false
+ }
+
+ var err error
+ *path, err = filepath.Abs(*path)
+
+ if err != nil {
+ logger.Printf("Error: %s", err.Error())
+ return false
+ }
+
+ if _, err = os.Stat(*path); os.IsNotExist(err) {
+ return false
+ }
+
+ return true
+}
+func usage() {
+ flag.Usage()
+ os.Exit(3)
}
diff --git a/glrdomon_test.go b/glrdomon_test.go
index 20adc558af09104ef2afa9443c5a6f5ab31bf7bd..67330b1cd61359b6288df190dfbf30f370bebd06 100644
--- a/glrdomon_test.go
+++ b/glrdomon_test.go
@@ -1,3 +1,47 @@
package main
-import "testing"
+import (
+ "testing"
+ "time"
+
+ "github.com/digitalocean/godo"
+)
+
+func TestCheckDropletAge(t *testing.T) {
+ staleDroplet := godo.Droplet{
+ ID: 1234,
+ Name: "very-old",
+ Created: "2000-08-19T19:07:04Z",
+ }
+
+ if !checkDropletAge(staleDroplet) {
+ t.Error("Failed to assert that very old droplet is stale")
+ }
+
+ now := time.Now()
+ newDroplet := godo.Droplet{
+ ID: 5678,
+ Name: "new",
+ Created: now.Format(time.RFC3339),
+ }
+
+ if checkDropletAge(newDroplet) {
+ t.Error("Asserted that brand-new droplet is stale")
+ }
+}
+
+func TestValidatePath(t *testing.T) {
+ emptyString := ""
+ notValid := validatePath(&emptyString)
+
+ if notValid == true {
+ t.Error("Empty path shouldn't validate")
+ }
+
+ sampleConfig := "./config-sample.json"
+ valid := validatePath(&sampleConfig)
+
+ if valid != true {
+ t.Error("Couldn't validate path to sample config")
+ }
+}