Add GZipMiddleware to compress JSON responses on-the-fly (#2308)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Matthew Evans <git@ml-evs.science>

Author: 3 people

optimade/server/config.py

@@ -8,6 +8,7 @@
 import yaml
 from pydantic import (
     AnyHttpUrl,
+    BaseModel,
     Field,
     NonNegativeFloat,
     field_validator,
@@ -145,6 +146,25 @@ def __call__(self) -> dict[str, Any]:
         return self.parse_config_file()
 
 
+class GZipConfig(BaseModel):
+    enabled: Annotated[
+        bool,
+        Field(description="Enable GZip compression for API responses."),
+    ] = False
+
+    minimum_size: Annotated[
+        int,
+        Field(
+            description="Minimum response size (in bytes) before compression is applied."
+        ),
+    ] = 5000
+
+    compresslevel: Annotated[
+        int,
+        Field(description="Compression level (1=fastest, 9=best compression)."),
+    ] = 3
+
+
 class ServerConfig(BaseSettings):
     """This class stores server config parameters in a way that
     can be easily extended for new config file types.
@@ -199,6 +219,11 @@ class ServerConfig(BaseSettings):
         ),
     ] = False
 
+    gzip: Annotated[
+        GZipConfig,
+        Field(description="Configuration options for GZip compression."),
+    ] = GZipConfig()
+
     use_real_mongo: Annotated[
         bool | None,
         Field(description="DEPRECATED: force usage of MongoDB over any other backend."),

optimade/server/main.py

@@ -13,6 +13,7 @@
 
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
+from fastapi.middleware.gzip import GZipMiddleware
 
 with warnings.catch_warnings(record=True) as w:
     from optimade.server.config import CONFIG, DEFAULT_CONFIG_FILE_PATH
@@ -144,6 +145,15 @@ def load_entries(endpoint_name: str, endpoint_collection: EntryCollection):
 for middleware in OPTIMADE_MIDDLEWARE:
     app.add_middleware(middleware)
 
+# Enable GZIP after other middleware.
+if CONFIG.gzip.enabled:
+    app.add_middleware(
+        GZipMiddleware,
+        minimum_size=CONFIG.gzip.minimum_size,
+        compresslevel=CONFIG.gzip.compresslevel,
+    )
+
+
 # Add exception handlers
 for exception, handler in OPTIMADE_EXCEPTIONS:
     app.add_exception_handler(exception, handler)

tests/test_config.json

@@ -2,6 +2,7 @@
     "debug": false,
     "default_db": "test_server",
     "base_url": "http://example.org",
+    "gzip": {"enabled": true},
     "implementation": {
         "name": "Example implementation",
         "source_url": "https://github.com/Materials-Consortia/optimade-python-tools",