Add retry backoff max and jitter settings [RHELDST-32465]

Previously these paramters used for urllib3's Retry were unset. Backoff
max defaulted to 120, which was too low for Akamai's strict rate
limiting. Jitter was also added to better spread requests, improve
system stability.

Author: negillett

fastpurge/_client.py

@@ -106,6 +106,9 @@ class FastPurgeClient(object):
     MAX_RETRIES = int(os.environ.get("FAST_PURGE_MAX_RETRIES", "10"))
 
     RETRY_BACKOFF = float(os.environ.get("FAST_PURGE_RETRY_BACKOFF", "0.15"))
+    RETRY_BACKOFF_MAX = float(os.environ.get("FAST_PURGE_RETRY_BACKOFF_MAX", "150"))
+    RETRY_BACKOFF_JITTER = float(os.environ.get("FAST_PURGE_RETRY_JITTER", "2"))
+
     # Default purge type.
     # Akamai recommend "invalidate", so why is "delete" our default?
     # Here's what Akamai docs have to say:
@@ -235,6 +238,8 @@ def __retry_policy(self):
             retries = LoggingRetry(
                 total=self.MAX_RETRIES,
                 backoff_factor=self.RETRY_BACKOFF,
+                backoff_max=self.RETRY_BACKOFF_MAX,
+                backoff_jitter=self.RETRY_BACKOFF_JITTER,
                 # We strictly require 201 here since that's how the server
                 # tells us we queued something async, as expected
                 status_forcelist=[status.value for status in HTTPStatus