From 4bb3a78059a1412b1b784c61bd6d7aad62f43157 Mon Sep 17 00:00:00 2001
From: Ruslan <rmashinistov@gmail.com>
Date: Thu, 2 Jan 2025 12:45:49 +0100
Subject: [PATCH] Split read-only and read/write API by the db backends

---
 nopayloaddb/db_router.py  | 29 +++++++++++++++++++++++
 nopayloaddb/middleware.py | 20 ++++++++++++++++
 nopayloaddb/settings.py   | 49 ++++++++++++++++++++++++++++++++++-----
 3 files changed, 92 insertions(+), 6 deletions(-)
 create mode 100644 nopayloaddb/db_router.py
 create mode 100644 nopayloaddb/middleware.py

diff --git a/nopayloaddb/db_router.py b/nopayloaddb/db_router.py
new file mode 100644
index 0000000..e8e8cf8
--- /dev/null
+++ b/nopayloaddb/db_router.py
@@ -0,0 +1,29 @@
+import random
+from nopayloaddb.middleware import get_current_request
+
+logger = logging.getLogger(__name__)
+
+class ReadWriteRouter:
+    def db_for_read(self, model, **hints):
+        """Route read queries to one of the read databases."""
+        db = random.choice(['read_db_1', 'read_db_2'])
+        # Check if request information is available
+        request = get_current_request()
+        if request and request.method == 'GET':
+            return db
+        return 'default'
+
+    def db_for_write(self, model, **hints):
+        """Route write queries to the default database."""
+        return 'default'
+
+    def allow_relation(self, obj1, obj2, **hints):
+        """Allow any relation if both objects are in the same database."""
+        db_set = {'default', 'read_db_1', 'read_db_2'}
+        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):
+        """Ensure migrations only run on the default database."""
+        return db == 'default'
diff --git a/nopayloaddb/middleware.py b/nopayloaddb/middleware.py
new file mode 100644
index 0000000..cfb90d6
--- /dev/null
+++ b/nopayloaddb/middleware.py
@@ -0,0 +1,20 @@
+from threading import local
+
+# Local storage for storing the current request
+_request_local = local()
+
+def get_current_request():
+    return getattr(_request_local, 'request', None)
+
+class RequestMiddleware:
+    """Middleware to store the current request for use in the DB router."""
+    def __init__(self, get_response):
+        self.get_response = get_response
+
+    def __call__(self, request):
+        # Save the request in the local thread storage
+        _request_local.request = request
+        response = self.get_response(request)
+        # Clear the request after processing to avoid conflicts
+        _request_local.request = None
+        return response
\ No newline at end of file
diff --git a/nopayloaddb/settings.py b/nopayloaddb/settings.py
index bc84ce8..cc9211d 100644
--- a/nopayloaddb/settings.py
+++ b/nopayloaddb/settings.py
@@ -53,6 +53,8 @@
     'django.contrib.auth.middleware.AuthenticationMiddleware',
     'django.contrib.messages.middleware.MessageMiddleware',
     'django.middleware.clickjacking.XFrameOptionsMiddleware',
+    #My middleware
+    'nopayloaddb.middleware.RequestMiddleware',
 ]
 
 ROOT_URLCONF = 'nopayloaddb.urls'
@@ -116,20 +118,55 @@
 #    }
 #}
 
+#DATABASES = {
+#    'default': {
+#        'ENGINE': 'django.db.backends.postgresql_psycopg2',
+#
+#
+#        'NAME':     os.environ.get("POSTGRES_DB",       default='dbname'),
+#        'USER':     os.environ.get("POSTGRES_USER",     default='login'),
+#        'PASSWORD': os.environ.get("POSTGRES_PASSWORD", default='password'),
+#        'HOST':     os.environ.get("POSTGRES_HOST",     default='localhost'),
+#        'PORT':     os.environ.get("POSTGRES_PORT",     default='5432'),
+#
+#    }
+#}
+
 DATABASES = {
     'default': {
         'ENGINE': 'django.db.backends.postgresql_psycopg2',
 
 
-        'NAME':     os.environ.get("POSTGRES_DB",       default='dbname'),
-        'USER':     os.environ.get("POSTGRES_USER",     default='login'),
-        'PASSWORD': os.environ.get("POSTGRES_PASSWORD", default='password'),
-        'HOST':     os.environ.get("POSTGRES_HOST",     default='localhost'),
-        'PORT':     os.environ.get("POSTGRES_PORT",     default='5432'),
+        'NAME':     os.environ.get("POSTGRES_DB_W",       default='dbname'),
+        'USER':     os.environ.get("POSTGRES_USER_W",     default='login'),
+        'PASSWORD': os.environ.get("POSTGRES_PASSWORD_W", default='password'),
+        'HOST':     os.environ.get("POSTGRES_HOST_W",     default='localhost'),
+        'PORT':     os.environ.get("POSTGRES_PORT_W",     default='5432'),
+    },
+    'read_db_1': {
+        'ENGINE': 'django.db.backends.postgresql_psycopg2',
+
+
+        'NAME':     os.environ.get("POSTGRES_DB_R1",       default='dbname'),
+        'USER':     os.environ.get("POSTGRES_USER_R1",     default='login'),
+        'PASSWORD': os.environ.get("POSTGRES_PASSWORD_R1", default='password'),
+        'HOST':     os.environ.get("POSTGRES_HOST_R1",     default='localhost'),
+        'PORT':     os.environ.get("POSTGRES_PORT_R1",     default='5432'),
+    },
+    'read_db_2': {
+        'ENGINE': 'django.db.backends.postgresql_psycopg2',
 
-    }
+
+        'NAME':     os.environ.get("POSTGRES_DB_R2",       default='dbname'),
+        'USER':     os.environ.get("POSTGRES_USER_R2",     default='login'),
+        'PASSWORD': os.environ.get("POSTGRES_PASSWORD_R2", default='password'),
+        'HOST':     os.environ.get("POSTGRES_HOST_R2",     default='localhost'),
+        'PORT':     os.environ.get("POSTGRES_PORT_R2",     default='5432'),
+    },
 }
 
+DATABASE_ROUTERS = ['nopayloaddb.db_router.ReadWriteRouter']
+
 REST_FRAMEWORK = {
 #    'DEFAULT_AUTHENTICATION_CLASSES': (
 #        'rest_framework.authentication.TokenAuthentication',