From a2273a082f7397ed746d776acae33e306745718f Mon Sep 17 00:00:00 2001
From: Aleksandr Bogdanov <syn@syn.im>
Date: Thu, 24 Mar 2016 15:44:20 +0100
Subject: [PATCH] Locking template object for non-parallel-safe operations

---
 app/Services/CloudFormer/Sparkle.php | 92 +++++++++++++++++++++++++---
 1 file changed, 83 insertions(+), 9 deletions(-)

diff --git a/app/Services/CloudFormer/Sparkle.php b/app/Services/CloudFormer/Sparkle.php
index b0e8425..fb927a6 100644
--- a/app/Services/CloudFormer/Sparkle.php
+++ b/app/Services/CloudFormer/Sparkle.php
@@ -18,6 +18,8 @@ class Sparkle implements TemplateEngine {
 
     const REMOTE_HIGHCORE = 'highcore';
     const APP_SSH_PRIVKEY = 'app/id_rsa';
+    const TEMPLATE_LOCK_TIMEOUT = 10 * 1000000; //10 seconds
+    const KEYGEN_TIMEOUT = 5000;
 
     protected $authProvider;
 
@@ -26,7 +28,7 @@ protected function ensureKeyExists($storage_path)
         if(!file_exists($storage_path)){
             $cmd = sprintf('ssh-keygen -b 2048 -t rsa -f %s -q -N ""', escapeshellarg($storage_path));
             $process = new Process($cmd);
-            $process->setTimeout(5000);
+            $process->setTimeout(static::KEYGEN_TIMEOUT);
             $process->run();
             if ($process->getExitCode() !== 0) {
                 $text = 'Exit code: ' . $process->getExitCode();
@@ -48,13 +50,25 @@ public function updateTemplate(Template $template)
 
         $repo = Repository::openAuthenticated($repoPath, $this->getAuthProvider());
 
-        $repo->isInitialized() or $repo->init();
-        $repo->setRemote(self::REMOTE_HIGHCORE, $template->repository);
-        $repo->fetch(self::REMOTE_HIGHCORE);
-        $repo->reset(sprintf('%s/%s', self::REMOTE_HIGHCORE, $template->refspec), ResetCommand::RESET_HARD, true);
-        $repo->updateSubmodule(true, true, true);
+        return $this->exclusiveFor($template, function() use($template, $repo){
+            $repo->isInitialized() or $repo->init();
+            $repo->setRemote(self::REMOTE_HIGHCORE, $template->repository);
+            $repo->fetch(self::REMOTE_HIGHCORE);
 
-        return $repo->getCommit();
+            try{
+                $currentRevision = $repo->getCommit()->getSha(); //git show fails when missing refs/heads/master
+            }catch(\RuntimeException $e){
+                $currentRevision = null;
+            }
+
+            $targetRefspec = sprintf('%s/%s', self::REMOTE_HIGHCORE, $template->refspec);
+
+            if($currentRevision != $repo->getCommit($targetRefspec)->getSha()) {
+                $repo->reset($targetRefspec, ResetCommand::RESET_HARD, true);
+                $repo->updateSubmodule(true, true, true);
+            }
+            return $repo;
+        });
     }
 
     /**
@@ -76,8 +90,10 @@ public function getTemplate(Template $template, $stack_definition, $update = tru
         Log::debug(sprintf('Calling sparke for template %s in project %s: %s',
             $template->name, $template->project->name, $command->getCommandLine()));
 
-        //$exitCode = 0; //$command->run();
-        $exitCode = $command->run();
+        $exitCode = $this->exclusiveFor($template, function() use ($command) {
+            return $command->run();
+        });
+
         if ($exitCode) {
             throw new Exception($command->getErrorOutput());
         }
@@ -128,6 +144,9 @@ public function getComponents(Template $template) {
     private function getTemplatePath(Template $template) {
         return storage_path("app/projects/{$template->id}-{$template->name}");
     }
+    private function getLockPath(Template $template){
+        return storage_path(sprintf("app/locks/%d.lock", $template->id));
+    }
 
     /**
      * @inheritdoc
@@ -168,4 +187,59 @@ private function getAuthProvider()
         }
         return $this->authProvider;
     }
+
+    /**
+     * @param Template $template
+     * @param callable $f
+     * @return mixed
+     * @throws Exception
+     */
+    protected function exclusiveFor(Template $template, $f){
+        $lock = $this->acquireLock($template);
+        try {
+            $retval = $f();
+        }catch(\Exception $e){
+            $this->releaseLock($lock);
+            throw $e;
+        }
+        $this->releaseLock($lock);
+        return $retval;
+    }
+
+    protected function acquireLock(Template $template){
+        $handle = fopen($this->getLockPath($template), 'c');
+        if(!static::flock_t($handle, LOCK_EX, static::TEMPLATE_LOCK_TIMEOUT, 500)){
+            throw new \RuntimeException('Could not acquire Template repository lock at '.$this->getLockPath($template));
+        }
+        return $handle;
+    }
+
+    protected function releaseLock($handle){
+        fclose($handle);
+    }
+
+    private function flock_t ($lockfile, $locktype, $timeout_micro, $sleep_by_micro = 10000) {
+        if (!is_resource($lockfile)) {
+            throw new \InvalidArgumentException ('The $lockfile was not a file resource or the resource was closed.');
+        }
+        if ($sleep_by_micro < 1) {
+            throw new \InvalidArgumentException ('The $sleep_by_micro cannot be less than 1, or else an infinite loop.');
+        }
+        if ($timeout_micro < 1) {
+            $locked = flock ($lockfile, $locktype | LOCK_NB);
+        } else {
+            $count_micro = 0;
+            $locked = true;
+            while (!flock($lockfile, $locktype | LOCK_NB, $blocking)) {
+                if ($blocking AND (($count_micro += $sleep_by_micro) <= $timeout_micro)) {
+                    usleep($sleep_by_micro);
+                } else {
+                    $locked = false;
+                    break;
+                }
+            }
+        }
+        return $locked;
+    }
+
 }
\ No newline at end of file