Fix read replicas (#118)

* fix loading database urls

* modify db router allow_relation method

* Update sensorsafrica/router.py

Co-authored-by: Clemence Kyara <kilemensi@users.noreply.github.com>

* Update sensorsafrica/settings.py

Co-authored-by: Clemence Kyara <kilemensi@users.noreply.github.com>

Co-authored-by: Clemence Kyara <kilemensi@users.noreply.github.com>

Author: thepsalmist

sensorsafrica/router.py

@@ -16,10 +16,14 @@ def db_for_write(self, model, **hints):
 
     def allow_relation(self, obj1, obj2, **hints):
         """
-        Relations between objects are allowed if both objects are
-        in the primary/replica pool.
+        Relation not applicable for our use case
         """
-        db_set = {'default', 'read_replica'}
-        if obj1._state.db in db_set and obj2._state.db in db_set:
-            return True
         return None
+    
+    def allow_migrate(self,db,app_label,model_name=None, **hints):
+        """
+        Restrict migration operations to the master db i.e. default
+        """
+        return db == "default"
+
+

sensorsafrica/settings.py

@@ -110,10 +110,10 @@
     "postgres://sensorsafrica:sensorsafrica@localhost:5432/sensorsafrica",
 )
 
-READ_DATABASE_URLS = os.getenv("SENSORSAFRICA_READ_DATABASE_URLS", DATABASE_URL).split(",")
-
 DATABASES = {"default": dj_database_url.parse(DATABASE_URL), }
 
+READ_DATABASE_URLS = os.getenv("SENSORSAFRICA_READ_DATABASE_URLS", DATABASE_URL).split(",")
+
 for index, read_database_url in enumerate(READ_DATABASE_URLS,start=1):
     DATABASES[f"read_replica_{index}"] = dj_database_url.parse(read_database_url)