nix: add --method for postgrest-loadtest

Currently the `postgrest-loadtest -k jwt-*` loadtests use the OPTIONS method,
which is good for isolating the perf changes for JWT auth.

But using GET is more accurate for actual perf improvements,
since it actually hits the database.

This adds a method argument for postgrest-loadtest, so GET can be used like:

```
postgrest-loadtest -k jwt-hs --method GET
```

CI is not changed, this is mostly useful for manually checking variance.

nix/tools/generate_targets.py

@@ -18,6 +18,7 @@ import jwt
 import jwcrypto.jwk as jwk
 from typing import Optional
 from pathlib import Path
+from enum import Enum
 
 URL = "http://postgrest"
 
@@ -44,8 +45,21 @@ def generate_jwt(now: int, exp_inc: Optional[int], is_hs: bool) -> str:
     return jwt.encode(payload, k, alg)
 
 
-def append_targets(lines: list[str], token: str):
-    lines.append(f"OPTIONS {URL}/authors_only")
+HTTP_METHODS = (
+    "GET",
+    "OPTIONS",
+)
+
+HttpMethod = Enum(
+    "HttpMethod",
+    {method: method for method in HTTP_METHODS},
+    type=str,
+    module=__name__,
+)
+
+
+def append_targets(lines: list[str], token: str, http_method: HttpMethod):
+    lines.append(f"{http_method.value} {URL}/authors_only")
     lines.append(f"Authorization: Bearer {token}")
     lines.append("")  # blank line to separate requests
 
@@ -73,11 +87,20 @@ def main():
         default=None,
         help="Path for generating a RSA JWK file to sign tokens with",
     )
+    parser.add_argument(
+        "--method",
+        dest="http_method",
+        choices=list(HTTP_METHODS),
+        default=None,
+        help="HTTP method for the vegeta targets",
+    )
 
     args = parser.parse_args()
 
     is_hs = args.jwk_path is None
 
+    http_method = HttpMethod(args.http_method)
+
     nsamples = 1000
     if is_hs:
         ntargets = 200000
@@ -122,13 +145,13 @@ def main():
 
         for i in range(ntargets):
             token = generate_jwt(now, inc + i // 1000, is_hs)
-            append_targets(lines, token)
+            append_targets(lines, token, http_method)
 
     else:
         tokens = [generate_jwt(now, None, is_hs) for _ in range(nsamples)]
         for i in range(ntargets):
             token = random.choice(tokens)
-            append_targets(lines, token)
+            append_targets(lines, token, http_method)
 
     try:
         with open(args.output, "w") as f: