From 5dc322c93eb3b92324c4f947697d2a2c69749040 Mon Sep 17 00:00:00 2001
From: Bryan Newbold <bnewbold@robocracy.org>
Date: Wed, 6 Mar 2019 11:39:36 -0800
Subject: retry/backoff for Crossref harvester

---
 python/fatcat_tools/harvest/doi_registrars.py |  4 ++--
 python/fatcat_tools/harvest/harvest_common.py | 22 ++++++++++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/python/fatcat_tools/harvest/doi_registrars.py b/python/fatcat_tools/harvest/doi_registrars.py
index 55d85ef9..1aaad56a 100644
--- a/python/fatcat_tools/harvest/doi_registrars.py
+++ b/python/fatcat_tools/harvest/doi_registrars.py
@@ -10,7 +10,7 @@ import requests
 from pykafka import KafkaClient
 
 from fatcat_tools.workers import most_recent_message
-from .harvest_common import HarvestState
+from .harvest_common import HarvestState, requests_retry_session
 
 
 class HarvestCrossrefWorker:
@@ -93,7 +93,7 @@ class HarvestCrossrefWorker:
         count = 0
         with produce_topic.get_producer() as producer:
             while True:
-                http_resp = requests.get(self.api_host_url, params, headers=headers)
+                http_resp = requests_retry_session().get(self.api_host_url, params, headers=headers)
                 if http_resp.status_code == 503:
                     # crude backoff
                     print("got HTTP {}, pausing for 30 seconds".format(http_resp.status_code))
diff --git a/python/fatcat_tools/harvest/harvest_common.py b/python/fatcat_tools/harvest/harvest_common.py
index f4d74be2..11fd5fe8 100644
--- a/python/fatcat_tools/harvest/harvest_common.py
+++ b/python/fatcat_tools/harvest/harvest_common.py
@@ -3,10 +3,32 @@ import sys
 import json
 import time
 import datetime
+import requests
+from requests.adapters import HTTPAdapter
+from requests.packages.urllib3.util.retry import Retry
+
 
 # Used for parsing ISO date format (YYYY-MM-DD)
 DATE_FMT = "%Y-%m-%d"
 
+def requests_retry_session(retries=10, backoff_factor=3,
+        status_forcelist=(500, 502, 504), session=None):
+    """
+    From: https://www.peterbe.com/plog/best-practice-with-retries-with-requests
+    """
+    session = session or requests.Session()
+    retry = Retry(
+        total=retries,
+        read=retries,
+        connect=retries,
+        backoff_factor=backoff_factor,
+        status_forcelist=status_forcelist,
+    )
+    adapter = HTTPAdapter(max_retries=retry)
+    session.mount('http://', adapter)
+    session.mount('https://', adapter)
+    return session
+
 class HarvestState:
     """
     First version of this works with full days (dates)
-- 
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