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postgrest/nix/tools/generate_targets.py
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# generates a file to be used by the vegeta load testing tool
import time
import hmac
import hashlib
import base64
import json
import argparse
import sys
import random
SECRET = b"reallyreallyreallyreallyverysafe"
URL = "http://postgrest"
JWT_DURATION = 120
TOTAL_TARGETS = 50000 # tuned by hand to reduce result variance
def base64url_encode(data: bytes) -> str:
"""URL-safe Base64 encode without padding."""
return base64.urlsafe_b64encode(data).rstrip(b"=").decode("ascii")
def generate_jwt(exp_inc: int) -> str:
"""Generate an HS256 JWT"""
# Header & payload
header = {"alg": "HS256", "typ": "JWT"}
now = int(time.time())
payload = {
"sub": f"user_{random.getrandbits(32)}",
"iat": now,
"exp": now + exp_inc,
"role": "postgrest_test_author",
}
# Encode to JSON and then to Base64URL
header_b = json.dumps(header, separators=(",", ":")).encode()
payload_b = json.dumps(payload, separators=(",", ":")).encode()
header_b64 = base64url_encode(header_b)
payload_b64 = base64url_encode(payload_b)
# Sign (HMACSHA256) the "<header>.<payload>" string
signing_input = f"{header_b64}.{payload_b64}".encode()
signature = hmac.new(SECRET, signing_input, hashlib.sha256).digest()
signature_b64 = base64url_encode(signature)
return f"{header_b64}.{payload_b64}.{signature_b64}"
# We want to ensure 401 Unauthorized responses don't happen during
# JWT validation, this can happen when the jwt `exp` is too short.
# At the same time, we want to ensure the `exp` is not too big,
# so expires will occur and postgREST will have to clean cached expired JWTs.
def estimate_adequate_jwt_exp_increase(iteration: int) -> int:
# estimated time takes to build and run postgrest itself
build_run_postgrest_time = 2
# estimated time it takes to generate the targets file
file_generation_time = TOTAL_TARGETS // (10**-5)
# estimated exp time so some JWTs will expire
dynamic_exp_inc = iteration // 1000
return build_run_postgrest_time + file_generation_time + dynamic_exp_inc
def main():
parser = argparse.ArgumentParser(
description="Generate Vegeta targets with unique JWTs"
)
parser.add_argument(
"output",
help="Path to write the generated targets file",
)
args = parser.parse_args()
lines = []
start_time = time.time()
for i in range(TOTAL_TARGETS):
token = generate_jwt(estimate_adequate_jwt_exp_increase(i))
lines.append(f"OPTIONS {URL}/authors_only")
lines.append(f"Authorization: Bearer {token}")
lines.append("") # blank line to separate requests
try:
with open(args.output, "w") as f:
f.write("\n".join(lines))
except IOError as e:
print(f"Error writing to {args.output}: {e}", file=sys.stderr)
sys.exit(1)
elapsed = time.time() - start_time
print(f"Created {TOTAL_TARGETS} targets in {args.output} ({elapsed:.2f}s)")
if __name__ == "__main__":
main()