From 935c72119ac9ca273a1069728ab268204cda8e2d Mon Sep 17 00:00:00 2001
From: Zack Schiller <81022539+zacheryschiller@users.noreply.github.com>
Date: Wed, 15 Sep 2021 06:14:11 -0400
Subject: [PATCH] Add db read replica 3 (#9453)

* Updating read replica list to include #3

* Adding read_replica_3 to settings
---
 app/app/db.py       | 4 ++--
 app/app/settings.py | 3 ++-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/app/app/db.py b/app/app/db.py
index e52a7e27ed7..3ed9af5ff0c 100644
--- a/app/app/db.py
+++ b/app/app/db.py
@@ -9,7 +9,7 @@ def db_for_read(self, model, **hints):
         Reads go to a randomly-chosen replica if backend node
         Else go to default DB
         """
-        replicas = ['read_replica_1', 'read_replica_2']
+        replicas = ['read_replica_1', 'read_replica_2', 'read_replica_3']
         return random.choice(replicas)
 
     def db_for_write(self, model, **hints):
@@ -23,7 +23,7 @@ def allow_relation(self, obj1, obj2, **hints):
         Relations between objects are allowed if both objects are
         in the primary/replica pool.
         """
-        db_set = {'default', 'read_replica_1', 'read_replica_2'}
+        db_set = {'default', 'read_replica_1', 'read_replica_2', 'read_replica_3'}
         if obj1._state.db in db_set and obj2._state.db in db_set:
             return True
         return True # TODO: be more stringent about this IFF we ever have a situation in which diff tables are on diff DBs
diff --git a/app/app/settings.py b/app/app/settings.py
index f941a0cb6cf..938231c3194 100644
--- a/app/app/settings.py
+++ b/app/app/settings.py
@@ -211,7 +211,8 @@
     DATABASES = {
         'default': env.db(),
         'read_replica_1': env.db('READ_REPLICA_1_DATABASE_URL'),
-        'read_replica_2': env.db('READ_REPLICA_2_DATABASE_URL')
+        'read_replica_2': env.db('READ_REPLICA_2_DATABASE_URL'),
+        'read_replica_3': env.db('READ_REPLICA_3_DATABASE_URL')
         }
     DATABASE_ROUTERS = ['app.db.PrimaryDBRouter']