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d1dbb40362Tools for profiling Datasette's request/response cycle in-process with Python 3.15's profiling.sampling, plus the patches proposed by the study (one per optimisation, and ALL-combined.diff). The patches are not applied to the code. A report with measurements follows. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01F8mEgRS8swZfYqwqrVMeo5
79 lines
2.9 KiB
Diff
79 lines
2.9 KiB
Diff
diff --git a/datasette/utils/__init__.py b/datasette/utils/__init__.py
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index 669d04c..7843b9b 100644
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--- a/datasette/utils/__init__.py
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+++ b/datasette/utils/__init__.py
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@@ -1779,6 +1779,22 @@ def sha256_file(filepath, chunk_size=4096):
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return hasher.hexdigest()
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+_sha256_cache = {}
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+
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+
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+def cached_sha256_file(filepath, chunk_size=4096):
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+ # Re-hash only if the file has changed. st_ctime_ns cannot be set by
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+ # tools that preserve mtime (cp -p, tar), st_ino catches replaced files
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+ stat = os.stat(filepath)
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+ key = (stat.st_ino, stat.st_size, stat.st_mtime_ns, stat.st_ctime_ns)
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+ cached = _sha256_cache.get(filepath)
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+ if cached is not None and cached[0] == key:
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+ return cached[1]
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+ digest = sha256_file(filepath, chunk_size=chunk_size)
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+ _sha256_cache[filepath] = (key, digest)
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+ return digest
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+
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+
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async def calculate_etag(filepath, chunk_size=4096):
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if filepath in _etag_cache:
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return _etag_cache[filepath]
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diff --git a/datasette/utils/asgi.py b/datasette/utils/asgi.py
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index 2d4a6cf..64d47be 100644
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--- a/datasette/utils/asgi.py
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+++ b/datasette/utils/asgi.py
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@@ -9,7 +9,12 @@ from urllib.parse import parse_qs, parse_qsl, urlunparse
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import aiofiles
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import aiofiles.os
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-from datasette.utils import MultiParams, calculate_etag, error_body, sha256_file
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+from datasette.utils import (
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+ MultiParams,
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+ cached_sha256_file,
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+ calculate_etag,
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+ error_body,
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+)
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from datasette.utils.multipart import (
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DEFAULT_MAX_FIELD_SIZE,
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DEFAULT_MAX_FIELDS,
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@@ -496,7 +501,8 @@ def asgi_static(root_path, chunk_size=4096, headers=None, content_type=None):
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hash_value = request.args.get("_hash")
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if (
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hash_value
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- and hash_value == sha256_file(full_path, chunk_size=chunk_size)[:12]
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+ and hash_value
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+ == cached_sha256_file(full_path, chunk_size=chunk_size)[:12]
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):
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headers["Cache-Control"] = HASHED_STATIC_CACHE_CONTROL
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etag = await calculate_etag(full_path, chunk_size=chunk_size)
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diff --git a/tests/test_utils.py b/tests/test_utils.py
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index 68d4a50..2de1d51 100644
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--- a/tests/test_utils.py
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+++ b/tests/test_utils.py
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@@ -923,6 +923,19 @@ def test_sha256_file(tmp_path):
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assert utils.sha256_file(path, chunk_size=2) == hashlib.sha256(b"hello").hexdigest()
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+def test_cached_sha256_file(tmp_path):
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+ path = tmp_path / "test.txt"
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+ path.write_text("hello")
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+ assert utils.cached_sha256_file(path) == hashlib.sha256(b"hello").hexdigest()
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+ key, _ = utils._sha256_cache[path]
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+ utils._sha256_cache[path] = (key, "cached")
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+ assert utils.cached_sha256_file(path) == "cached"
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+ # Modifying the file invalidates the cached hash
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+ path.write_text("hello!")
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+ assert utils.cached_sha256_file(path) == hashlib.sha256(b"hello!").hexdigest()
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+ utils._sha256_cache.clear()
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+
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+
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@pytest.mark.asyncio
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async def test_calculate_etag(tmp_path):
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path = tmp_path / "test.txt"
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