feat: Accept numbered replica database URLs

api/app/settings/common.py

@@ -27,6 +27,7 @@
 from task_processor.task_run_method import TaskRunMethod  # type: ignore[import-untyped]
 
 from app.routers import ReplicaReadStrategy
+from app.utils import get_numbered_env_vars_with_prefix
 
 env = Env()
 
@@ -176,8 +177,14 @@
         ),
     }
     REPLICA_DATABASE_URLS_DELIMITER = env("REPLICA_DATABASE_URLS_DELIMITER", ",")
-    REPLICA_DATABASE_URLS = env.list(
-        "REPLICA_DATABASE_URLS", default=[], delimiter=REPLICA_DATABASE_URLS_DELIMITER
+    REPLICA_DATABASE_URLS = (
+        env.list(
+            "REPLICA_DATABASE_URLS",
+            default=[],
+            delimiter=REPLICA_DATABASE_URLS_DELIMITER,
+        )
+        if not os.getenv("REPLICA_DATABASE_URL_0")
+        else get_numbered_env_vars_with_prefix("REPLICA_DATABASE_URL_")
     )
     NUM_DB_REPLICAS = len(REPLICA_DATABASE_URLS)
 
@@ -186,10 +193,14 @@
     CROSS_REGION_REPLICA_DATABASE_URLS_DELIMITER = env(
         "CROSS_REGION_REPLICA_DATABASE_URLS_DELIMITER", ","
     )
-    CROSS_REGION_REPLICA_DATABASE_URLS = env.list(
-        "CROSS_REGION_REPLICA_DATABASE_URLS",
-        default=[],
-        delimiter=CROSS_REGION_REPLICA_DATABASE_URLS_DELIMITER,
+    CROSS_REGION_REPLICA_DATABASE_URLS = (
+        env.list(
+            "CROSS_REGION_REPLICA_DATABASE_URLS",
+            default=[],
+            delimiter=CROSS_REGION_REPLICA_DATABASE_URLS_DELIMITER,
+        )
+        if not os.getenv("CROSS_REGION_REPLICA_DATABASE_URL_0")
+        else get_numbered_env_vars_with_prefix("CROSS_REGION_REPLICA_DATABASE_URL_")
     )
     NUM_CROSS_REGION_DB_REPLICAS = len(CROSS_REGION_REPLICA_DATABASE_URLS)
 

api/app/utils.py

@@ -1,4 +1,5 @@
 import json
+import os
 import pathlib
 from functools import lru_cache
 from typing import TypedDict
@@ -73,3 +74,19 @@ def _get_file_contents(file_path: str) -> str:
             return f.read().replace("\n", "")
     except FileNotFoundError:
         return UNKNOWN
+
+
+def get_numbered_env_vars_with_prefix(prefix: str) -> list[str]:
+    """
+    Returns a list containing the values of all environment variables whose names have a given prefix followed by an
+    integer, starting from 0, until no more variables with that prefix are found.
+    """
+    db_urls = []
+    i = 0
+    while True:
+        db_url = os.getenv(f"{prefix}{i}")
+        if not db_url:
+            break
+        db_urls.append(db_url)
+        i += 1
+    return db_urls

api/tests/unit/app/test_unit_app_utils.py

@@ -4,7 +4,7 @@
 from pyfakefs.fake_filesystem import FakeFilesystem
 from pytest_django.fixtures import SettingsWrapper
 
-from app.utils import get_version_info
+from app.utils import get_numbered_env_vars_with_prefix, get_version_info
 
 
 def test_get_version_info(fs: FakeFilesystem) -> None:
@@ -97,3 +97,16 @@ def test_get_version_info__email_config_disabled__return_expected(
 
     # Then
     assert result["has_email_provider"] is False
+
+
+def test_get_numbered_env_vars_with_prefix(monkeypatch: pytest.MonkeyPatch) -> None:
+    # Given
+    monkeypatch.setenv("DB_URL_0", "0")
+    monkeypatch.setenv("DB_URL_1", "1")
+    monkeypatch.setenv("DB_URL_3", "3")
+
+    # When
+    env_vars = get_numbered_env_vars_with_prefix("DB_URL_")
+
+    # Then
+    assert env_vars == ["0", "1"]