From efddcefb88d590df5de50211e371c38ca86981a8 Mon Sep 17 00:00:00 2001
From: Mathieu Leplatre <mathieu@mozilla.com>
Date: Mon, 28 Sep 2020 19:34:03 +0200
Subject: [PATCH 1/4] Raise 307 redirect before storage hit

---
 kinto_changes/views.py | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/kinto_changes/views.py b/kinto_changes/views.py
index ab619e0..a131808 100644
--- a/kinto_changes/views.py
+++ b/kinto_changes/views.py
@@ -90,6 +90,9 @@ class Changes(resource.Resource):
     schema = ChangesSchema
 
     def __init__(self, request, context=None):
+        # Bypass call to storage if _since is too old.
+        _handle_old_since_redirect(request)
+
         super(Changes, self).__init__(request, context)
         self.model = ChangesModel(request)
 
@@ -99,7 +102,6 @@ def timestamp(self):
 
     def plural_get(self):
         result = super().plural_get()
-        _handle_old_since_redirect(self.request)
         _handle_cache_expires(self.request, MONITOR_BUCKET, CHANGES_COLLECTION)
         return result
 
@@ -135,8 +137,13 @@ def _handle_old_since_redirect(request):
     See https://bugzilla.mozilla.org/show_bug.cgi?id=1529685
     and https://bugzilla.mozilla.org/show_bug.cgi?id=1665319#c2
     """
-    qs_since = request.validated["querystring"].get("_since")
-    if qs_since is None:
+    try:
+        # request.validated is not populated yet (resource was not instantiated yet,
+        # we want to bypass storage).
+        qs_since_str = request.GET.get("_since", "")
+        qs_since = int(qs_since_str.strip('"'))
+    except (TypeError, ValueError):
+        # Will fail later during resource querystring validation.
         return
 
     settings = request.registry.settings
@@ -240,13 +247,13 @@ def get_changeset(request):
         include_deleted = True
 
     if (bid, cid) == (MONITOR_BUCKET, CHANGES_COLLECTION):
-        model = ChangesModel(request)
+        # Redirect old since, on monitor/changes only.
+        _handle_old_since_redirect(request)
 
+        model = ChangesModel(request)
         metadata = {}
         timestamp = model.timestamp()
         changes = model.get_objects(filters=filters, include_deleted=include_deleted)
-        # Redirect old since, on monitor/changes only.
-        _handle_old_since_redirect(request)
 
     else:
         bucket_uri = instance_uri(request, "bucket", id=bid)

From 1993cce4349d967cb587bd5b732c5f96617e5815 Mon Sep 17 00:00:00 2001
From: Mathieu Leplatre <mathieu@mozilla.com>
Date: Mon, 28 Sep 2020 19:34:34 +0200
Subject: [PATCH 2/4] Simplify inheritance by injecting model before resource
 init

---
 kinto_changes/views.py | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/kinto_changes/views.py b/kinto_changes/views.py
index a131808..0bf07bc 100644
--- a/kinto_changes/views.py
+++ b/kinto_changes/views.py
@@ -92,13 +92,9 @@ class Changes(resource.Resource):
     def __init__(self, request, context=None):
         # Bypass call to storage if _since is too old.
         _handle_old_since_redirect(request)
-
-        super(Changes, self).__init__(request, context)
+        # Inject custom model.
         self.model = ChangesModel(request)
-
-    @property
-    def timestamp(self):
-        return self.model.timestamp()
+        super(Changes, self).__init__(request, context)
 
     def plural_get(self):
         result = super().plural_get()

From 624ab223dad11a41e980ab6612a61c6d43325e13 Mon Sep 17 00:00:00 2001
From: Mathieu Leplatre <mathieu@mozilla.com>
Date: Mon, 28 Sep 2020 19:35:15 +0200
Subject: [PATCH 3/4] Update CHANGELOG

---
 CHANGELOG.rst | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index cbe6225..6853b5a 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -4,7 +4,9 @@ Changelog
 3.2.0 (unreleased)
 ------------------
 
-- Nothing changed yet.
+**Bug fixes**
+
+- Bypass storage when redirecting on old ``_since``
 
 
 3.1.0 (2020-09-22)

From e03bae7e66e92c59ac9001697762144e33c43572 Mon Sep 17 00:00:00 2001
From: Mathieu Leplatre <mathieu@mozilla.com>
Date: Mon, 28 Sep 2020 21:46:09 +0200
Subject: [PATCH 4/4] Remove superfluous TypeError

---
 kinto_changes/views.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kinto_changes/views.py b/kinto_changes/views.py
index 0bf07bc..9953860 100644
--- a/kinto_changes/views.py
+++ b/kinto_changes/views.py
@@ -138,7 +138,7 @@ def _handle_old_since_redirect(request):
         # we want to bypass storage).
         qs_since_str = request.GET.get("_since", "")
         qs_since = int(qs_since_str.strip('"'))
-    except (TypeError, ValueError):
+    except ValueError:
         # Will fail later during resource querystring validation.
         return