feat: Each replica database URL can now be configured with an individual environment variable, using REPLICA_DATABASE_URL_0, REPLICA_DATABASE_URL_1, etc (#5222)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: rolodato

api/app/settings/common.py

@@ -28,6 +28,7 @@
 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()
 
@@ -177,11 +178,15 @@
         ),
     }
     REPLICA_DATABASE_URLS_DELIMITER = env("REPLICA_DATABASE_URLS_DELIMITER", ",")
-    REPLICA_DATABASE_URLS = env.list(
-        "REPLICA_DATABASE_URLS",
-        subcast=str,
-        default=[],
-        delimiter=REPLICA_DATABASE_URLS_DELIMITER,
+    REPLICA_DATABASE_URLS = (
+        env.list(
+            "REPLICA_DATABASE_URLS",
+            subcast=str,
+            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)
 
@@ -190,11 +195,15 @@
     CROSS_REGION_REPLICA_DATABASE_URLS_DELIMITER = env(
         "CROSS_REGION_REPLICA_DATABASE_URLS_DELIMITER", ","
     )
-    CROSS_REGION_REPLICA_DATABASE_URLS: list[str] = env.list(
-        "CROSS_REGION_REPLICA_DATABASE_URLS",
-        subcast=str,
-        default=[],
-        delimiter=CROSS_REGION_REPLICA_DATABASE_URLS_DELIMITER,
+    CROSS_REGION_REPLICA_DATABASE_URLS = (
+        env.list(
+            "CROSS_REGION_REPLICA_DATABASE_URLS",
+            subcast=str,
+            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

@@ -1,6 +1,24 @@
+import os
+
 import shortuuid
 
 
 def create_hash() -> str:
     """Helper function to create a short hash"""
     return shortuuid.uuid()
+
+
+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

@@ -0,0 +1,16 @@
+import pytest
+
+from app.utils import get_numbered_env_vars_with_prefix
+
+
+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"]