[PATCH proxmox v2 3/3] fix #6858: s3-client: retry request on 500, 503 and 504 status codes

[Christian Ebner <c.ebner@proxmox.com>]

Follow the best practices for AWS S3 error handling [0] and perform
retries on requests with http status code 500 or 503 in the response.

Further, do the same for 504 gateway timeout errors encountered by
some users in the community forum [1] in combination with Hetzner's
S3 storage offerings.

This is done for all requests unconditionally, maximum number of
retires and optional request timeout being honored.

[0] https://docs.aws.amazon.com/AmazonS3/latest/API/ErrorBestPractices.html
[1] https://forum.proxmox.com/threads/180956/

Fixes: https://bugzilla.proxmox.com/show_bug.cgi?id=6858
Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
---
changes since version 1:
- return the last error if retries are exhausted
- consider also 504 gateway timeout as retryable

 proxmox-s3-client/src/client.rs | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/proxmox-s3-client/src/client.rs b/proxmox-s3-client/src/client.rs
index f3e5eb45..35c80948 100644
--- a/proxmox-s3-client/src/client.rs
+++ b/proxmox-s3-client/src/client.rs
@@ -388,13 +388,18 @@ impl S3Client {
                 self.client.request(request).await
             };
 
-            match response {
-                Ok(response) => return Ok(response),
-                Err(err) => {
-                    if retry >= MAX_S3_HTTP_REQUEST_RETRY - 1 {
-                        return Err(err.into());
-                    }
-                }
+            let do_retry = match &response {
+                Ok(response) => matches!(
+                    response.status(),
+                    StatusCode::INTERNAL_SERVER_ERROR
+                        | StatusCode::SERVICE_UNAVAILABLE
+                        | StatusCode::GATEWAY_TIMEOUT
+                ),
+                Err(_) => true,
+            };
+
+            if !do_retry || retry >= MAX_S3_HTTP_REQUEST_RETRY - 1 {
+                return Ok(response?);
             }
 
             let backoff_secs = S3_HTTP_REQUEST_RETRY_BACKOFF_DEFAULT * 3_u32.pow(retry as u32);
-- 
2.47.3