Add retry on locks

Author: Fabianoshz

server/events/working_dir_locker.go

@@ -17,6 +17,7 @@ import (
 	"fmt"
 	"strings"
 	"sync"
+	"time"
 )
 
 //go:generate pegomock generate --package mocks -o mocks/mock_working_dir_locker.go WorkingDirLocker
@@ -78,19 +79,35 @@ func (d *DefaultWorkingDirLocker) TryLock(repoFullName string, pullNum int, work
 	d.mutex.Lock()
 	defer d.mutex.Unlock()
 
-	pullKey := d.pullKey(repoFullName, pullNum)
-	workspaceKey := d.workspaceKey(repoFullName, pullNum, workspace, path)
-	for _, l := range d.locks {
-		if l == pullKey || l == workspaceKey {
-			return func() {}, fmt.Errorf("the %s workspace at path %s is currently locked by another"+
-				" command that is running for this pull request.\n"+
-				"Wait until the previous command is complete and try again", workspace, path)
+	ticker := time.NewTicker(time.Second)
+	timeout := time.NewTimer(600 * time.Second)
+	addLock := false
+
+	for {
+		workspaceKey := d.workspaceKey(repoFullName, pullNum, workspace, path)
+
+		if addLock || len(d.locks) == 0 {
+			d.locks = append(d.locks, workspaceKey)
+			return func() {
+				d.unlock(repoFullName, pullNum, workspace, path)
+			}, nil
 		}
+
+		select {
+		case <-timeout.C:
+			return func() {}, fmt.Errorf("the Atlantis working dir is currently locked by another" +
+				" command that is running for this pull request.\n" +
+				"Wait until the previous command is complete and try again")
+		case <-ticker.C:
+			for _, l := range d.locks {
+				pullKey := d.pullKey(repoFullName, pullNum)
+				if l != pullKey && l != workspaceKey {
+					addLock = true
+				}
+			}
+		}
+
 	}
-	d.locks = append(d.locks, workspaceKey)
-	return func() {
-		d.unlock(repoFullName, pullNum, workspace, path)
-	}, nil
 }
 
 // Unlock unlocks the workspace for this pull.