fix: handle empty 'Retry-After' header from GitLab

When requests are throttled (HTTP response code 429), python-gitlab
assumed that 'Retry-After' existed in the response headers. This is
not always the case and so the request fails due to a KeyError. The
change in this commit adds a rudimentary exponential backoff to the
'http_request' method, which defaults to 10 retries but can be set
to -1 to retry without bound.

1 files changed, 11 insertions, 3 deletions

diff --git a/gitlab/__init__.py b/gitlab/__init__.py
index 01f9426..c280974 100644
--- a/gitlab/__init__.py
+++ b/gitlab/__init__.py
@@ -477,6 +477,10 @@ class Gitlab(object):
         # obey the rate limit by default
         obey_rate_limit = kwargs.get("obey_rate_limit", True)
 
+        # set max_retries to 10 by default, disable by setting it to -1
+        max_retries = kwargs.get("max_retries", 10)
+        cur_retries = 0
+
         while True:
             result = self.session.send(prepped, timeout=timeout, **settings)
 
@@ -486,9 +490,13 @@ class Gitlab(object):
                 return result
 
             if 429 == result.status_code and obey_rate_limit:
-                wait_time = int(result.headers["Retry-After"])
-                time.sleep(wait_time)
-                continue
+                if max_retries == -1 or cur_retries < max_retries:
+                    wait_time = 2 ** cur_retries * 0.1
+                    if "Retry-After" in result.headers:
+                        wait_time = int(result.headers["Retry-After"])
+                    cur_retries += 1
+                    time.sleep(wait_time)
+                    continue
 
             error_message = result.content
             try: