From 69422ffaa42cda7d2881c5925cab17e224e3f9a3 Mon Sep 17 00:00:00 2001
From: Andy Heathershaw <andy.heathershaw@premiersoftware.co.uk>
Date: Wed, 11 Sep 2019 14:59:25 +0100
Subject: [PATCH] Backblaze #135 - implemented a retry and backoff period for
 500/503 errors

---
 app/Exceptions/BackblazeRetryException.php | 25 +++++++++++++++++
 app/Services/BackblazeB2Service.php        | 32 +++++++++++++++++++++-
 2 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100644 app/Exceptions/BackblazeRetryException.php

diff --git a/app/Exceptions/BackblazeRetryException.php b/app/Exceptions/BackblazeRetryException.php
new file mode 100644
index 0000000..557ebfd
--- /dev/null
+++ b/app/Exceptions/BackblazeRetryException.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace App\Exceptions;
+
+use Throwable;
+
+class BackblazeRetryException extends \Exception
+{
+    private $innerException;
+
+    /**
+     * @return mixed
+     */
+    public function getInnerException()
+    {
+        return $this->innerException;
+    }
+
+    public function __construct($httpCode, \Exception $innerException)
+    {
+        parent::__construct('Backblaze requested to retry the request');
+
+        $this->innerException = $innerException;
+    }
+}
\ No newline at end of file
diff --git a/app/Services/BackblazeB2Service.php b/app/Services/BackblazeB2Service.php
index 2ffb95c..57149ee 100644
--- a/app/Services/BackblazeB2Service.php
+++ b/app/Services/BackblazeB2Service.php
@@ -2,6 +2,7 @@
 
 namespace App\Services;
 
+use App\Exceptions\BackblazeRetryException;
 use Illuminate\Support\Facades\Log;
 
 class BackblazeB2Service
@@ -238,6 +239,27 @@ class BackblazeB2Service
     }
 
     private function sendRequest($url, $method = 'GET', $postData = null, array $postOptions = [])
+    {
+        $exponentialBackoff = 1;
+        $numberOfRetries = 5; // this effectively gives us 31 seconds of retries (1+2+4+8+16)
+        $numberOfTimesTried = 0;
+
+        while ($numberOfTimesTried < $numberOfRetries)
+        {
+            try
+            {
+                return $this->sendRequestReal($url, $method, $postData, $postOptions);
+            }
+            catch (BackblazeRetryException $ex)
+            {
+                // Keep backing off
+                $exponentialBackoff *= $exponentialBackoff;
+                $numberOfTimesTried++;
+            }
+        }
+    }
+
+    private function sendRequestReal($url, $method = 'GET', $postData = null, array $postOptions = [])
     {
         $postOptions = array_merge(
             [
@@ -298,7 +320,15 @@ class BackblazeB2Service
         Log::info(sprintf('Received HTTP code %d', $httpCode));
         Log::debug($result);
 
-        if ($httpCode != 200 && $httpCode != 304)
+        // According to the Backblaze B2 Protocol, if we get a 500/503, we should retry the request
+        if ($httpCode == 500 || $httpCode == 503)
+        {
+            throw new BackblazeRetryException(
+                $httpCode,
+                new \Exception(sprintf('Exception from Backblaze B2: %s', $result))
+            );
+        }
+        else if ($httpCode != 200 && $httpCode != 304)
         {
             throw new \Exception(sprintf('Exception from Backblaze B2: %s', $result));
         }