mirror of
https://github.com/simonw/datasette.git
synced 2026-06-04 08:07:01 +02:00
31b21f5c5e
SQLite operations are blocking, but we're running everything in Sanic, an
asyncio web framework, so blocking operations are bad - a long-running DB
operation could hold up the entire server.
Instead, I've moved all SQLite operations into threads. These are managed by a
concurrent.futures ThreadPoolExecutor. This means I can run up to X queries in
parallel, and I can continue to queue up additional incoming HTTP traffic
while the threadpool is busy.
Each thread is responsible for managing its own SQLite connections - one per
database. These are cached in a threadlocal.
Since we are working with immutable, read-only SQLite databases it should be
safe to share SQLite objects across threads. On this assumption I'm using the
check_same_thread=False option. Opening a database connection looks like this:
conn = sqlite3.connect(
'file:filename.db?immutable=1',
uri=True,
check_same_thread=False,
)
The following articles were helpful in figuring this out:
* https://pymotw.com/3/asyncio/executors.html
* https://marlinux.wordpress.com/2017/05/19/python-3-6-asyncio-sqlalchemy/
Closes #45. Refs #38.
450 lines
14 KiB
Python
450 lines
14 KiB
Python
from sanic import Sanic
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from sanic import response
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from sanic.exceptions import NotFound
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from sanic.views import HTTPMethodView
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from sanic_jinja2 import SanicJinja2
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from jinja2 import FileSystemLoader
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import sqlite3
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from contextlib import contextmanager
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from pathlib import Path
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from functools import wraps
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from concurrent import futures
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import asyncio
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import threading
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import urllib.parse
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import json
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import base64
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import hashlib
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import sys
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import time
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app_root = Path(__file__).parent.parent
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BUILD_METADATA = 'build-metadata.json'
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DB_GLOBS = ('*.db', '*.sqlite', '*.sqlite3')
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HASH_BLOCK_SIZE = 1024 * 1024
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SQL_TIME_LIMIT_MS = 1000
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connections = threading.local()
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def ensure_build_metadata(regenerate=False):
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build_metadata = app_root / BUILD_METADATA
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if build_metadata.exists() and not regenerate:
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return json.loads(build_metadata.read_text())
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print('Building metadata... path={}'.format(build_metadata))
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metadata = {}
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for glob in DB_GLOBS:
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for path in app_root.glob(glob):
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print(' globbing, path={}'.format(path))
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name = path.stem
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if name in metadata:
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raise Exception('Multiple files with same stem %s' % name)
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# Calculate hash, efficiently
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m = hashlib.sha256()
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with path.open('rb') as fp:
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while True:
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data = fp.read(HASH_BLOCK_SIZE)
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if not data:
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break
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m.update(data)
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# List tables and their row counts
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tables = {}
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with sqlite3.connect('file:{}?immutable=1'.format(path.name), uri=True) as conn:
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conn.row_factory = sqlite3.Row
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table_names = [
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r['name']
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for r in conn.execute('select * from sqlite_master where type="table"')
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]
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for table in table_names:
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tables[table] = conn.execute('select count(*) from "{}"'.format(table)).fetchone()[0]
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metadata[name] = {
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'hash': m.hexdigest(),
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'file': path.name,
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'tables': tables,
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}
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build_metadata.write_text(json.dumps(metadata, indent=4))
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return metadata
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class BaseView(HTTPMethodView):
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template = None
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def __init__(self, jinja, executor):
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self.jinja = jinja
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self.executor = executor
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def redirect(self, request, path):
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if request.query_string:
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path = '{}?{}'.format(
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path, request.query_string
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)
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r = response.redirect(path)
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r.headers['Link'] = '<{}>; rel=preload'.format(path)
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return r
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async def pks_for_table(self, name, table):
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rows = [
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row for row in await self.execute(
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name,
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'PRAGMA table_info("{}")'.format(table)
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)
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if row[-1]
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]
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rows.sort(key=lambda row: row[-1])
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return [str(r[1]) for r in rows]
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async def execute(self, db_name, sql):
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"""Executes sql against db_name in a thread"""
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def sql_operation_in_thread():
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conn = getattr(connections, db_name, None)
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if not conn:
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info = ensure_build_metadata()[db_name]
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conn = sqlite3.connect(
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'file:{}?immutable=1'.format(info['file']),
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uri=True,
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check_same_thread=False,
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)
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conn.row_factory = sqlite3.Row
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conn.text_factory = lambda x: str(x, 'utf-8', 'replace')
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setattr(connections, db_name, conn)
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with sqlite_timelimit(conn, SQL_TIME_LIMIT_MS):
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rows = conn.execute(sql)
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return rows
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return await asyncio.get_event_loop().run_in_executor(
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self.executor, sql_operation_in_thread
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)
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async def get(self, request, db_name, **kwargs):
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name, hash, should_redirect = resolve_db_name(db_name, **kwargs)
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if should_redirect:
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return self.redirect(request, should_redirect)
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return await self.view_get(request, name, hash, **kwargs)
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async def view_get(self, request, name, hash, **kwargs):
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try:
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as_json = kwargs.pop('as_json')
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except KeyError:
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as_json = False
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extra_template_data = {}
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start = time.time()
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try:
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data, extra_template_data = await self.data(
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request, name, hash, **kwargs
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)
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except sqlite3.OperationalError as e:
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data = {
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'ok': False,
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'error': str(e),
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}
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end = time.time()
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data['took_ms'] = (end - start) * 1000
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if as_json:
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# Special case for .jsono extension
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if as_json == '.jsono':
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columns = data.get('columns')
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rows = data.get('rows')
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if rows and columns:
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data['rows'] = [
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dict(zip(columns, row))
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for row in rows
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]
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r = response.HTTPResponse(
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json.dumps(
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data, cls=CustomJSONEncoder
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),
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content_type='application/json',
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headers={
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'Access-Control-Allow-Origin': '*'
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}
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)
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else:
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context = {**data, **dict(
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extra_template_data()
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if callable(extra_template_data)
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else extra_template_data
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)}
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r = self.jinja.render(
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self.template,
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request,
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**context,
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)
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# Set far-future cache expiry
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r.headers['Cache-Control'] = 'max-age={}'.format(
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365 * 24 * 60 * 60
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)
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return r
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class IndexView(HTTPMethodView):
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def __init__(self, jinja, executor):
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self.jinja = jinja
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self.executor = executor
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async def get(self, request):
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databases = []
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for key, info in ensure_build_metadata().items():
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database = {
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'name': key,
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'hash': info['hash'],
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'path': '{}-{}'.format(key, info['hash'][:7]),
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'tables_truncated': sorted(
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info['tables'].items(),
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key=lambda p: p[1],
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reverse=True
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)[:5],
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'tables_count': len(info['tables'].items()),
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'tables_more': len(info['tables'].items()) > 5,
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'total_rows': sum(info['tables'].values()),
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}
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databases.append(database)
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return self.jinja.render(
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'index.html',
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request,
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databases=databases,
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)
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async def favicon(request):
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return response.text('')
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class DatabaseView(BaseView):
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template = 'database.html'
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async def data(self, request, name, hash):
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sql = request.args.get('sql') or 'select * from sqlite_master'
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rows = await self.execute(name, sql)
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columns = [r[0] for r in rows.description]
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return {
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'database': name,
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'rows': rows,
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'columns': columns,
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}, {
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'database_hash': hash,
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}
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class DatabaseDownload(BaseView):
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async def view_get(self, request, name, hash, **kwargs):
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filepath = ensure_build_metadata()[name]['file']
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return await response.file_stream(
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filepath, headers={
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'Content-Disposition': 'attachment; filename="{}"'.format(filepath)
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}
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)
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class TableView(BaseView):
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template = 'table.html'
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async def data(self, request, name, hash, table):
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table = urllib.parse.unquote_plus(table)
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if request.args:
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where_clause, params = build_where_clause(request.args)
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sql = 'select * from "{}" where {} limit 50'.format(
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table, where_clause
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)
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else:
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sql = 'select * from "{}" limit 50'.format(table)
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params = []
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rows = await self.execute(name, sql)
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columns = [r[0] for r in rows.description]
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rows = list(rows)
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pks = await self.pks_for_table(name, table)
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info = ensure_build_metadata()
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total_rows = info[name]['tables'].get(table)
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return {
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'database': name,
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'table': table,
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'rows': rows,
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'total_rows': total_rows,
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'columns': columns,
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'primary_keys': pks,
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}, lambda: {
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'database_hash': hash,
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'row_link': lambda row: path_from_row_pks(row, pks),
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}
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class RowView(BaseView):
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template = 'row.html'
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async def data(self, request, name, hash, table, pk_path):
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table = urllib.parse.unquote_plus(table)
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pk_values = compound_pks_from_path(pk_path)
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pks = await self.pks_for_table(name, table)
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wheres = [
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'"{}"=?'.format(pk)
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for pk in pks
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]
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sql = 'select * from "{}" where {}'.format(
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table, ' AND '.join(wheres)
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)
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rows = await self.execute(name, sql)
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columns = [r[0] for r in rows.description]
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rows = list(rows)
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if not rows:
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raise NotFound('Record not found: {}'.format(pk_values))
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return {
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'database': name,
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'table': table,
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'rows': rows,
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'columns': columns,
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'primary_keys': pks,
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}, {
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'database_hash': hash,
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'row_link': None,
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}
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def resolve_db_name(db_name, **kwargs):
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databases = ensure_build_metadata()
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hash = None
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name = None
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if '-' in db_name:
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# Might be name-and-hash, or might just be
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# a name with a hyphen in it
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name, hash = db_name.rsplit('-', 1)
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if name not in databases:
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# Try the whole name
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name = db_name
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hash = None
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else:
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name = db_name
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# Verify the hash
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try:
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info = databases[name]
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except KeyError:
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raise NotFound('Database not found: {}'.format(name))
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expected = info['hash'][:7]
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if expected != hash:
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should_redirect = '/{}-{}'.format(
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name, expected,
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)
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if 'table' in kwargs:
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should_redirect += '/' + kwargs['table']
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if 'as_json' in kwargs:
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should_redirect += kwargs['as_json']
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if 'as_db' in kwargs:
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should_redirect += kwargs['as_db']
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return name, expected, should_redirect
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return name, expected, None
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def compound_pks_from_path(path):
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return [
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urllib.parse.unquote_plus(b) for b in path.split(',')
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]
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def path_from_row_pks(row, pks):
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if not pks:
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return ''
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bits = []
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for pk in pks:
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bits.append(
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urllib.parse.quote_plus(str(row[pk]))
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)
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return ','.join(bits)
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def build_where_clause(args):
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sql_bits = []
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for key, values in args.items():
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if '__' in key:
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column, lookup = key.rsplit('__', 1)
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else:
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column = key
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lookup = 'exact'
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template = {
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'exact': '"{}" = ?',
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'contains': '"{}" like ?',
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'endswith': '"{}" like ?',
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'startswith': '"{}" like ?',
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'gt': '"{}" > ?',
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'gte': '"{}" >= ?',
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'lt': '"{}" < ?',
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'lte': '"{}" <= ?',
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'glob': '"{}" glob ?',
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'like': '"{}" like ?',
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}[lookup]
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value = values[0]
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value_convert = {
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'contains': lambda s: '%{}%'.format(s),
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'endswith': lambda s: '%{}'.format(s),
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'startswith': lambda s: '{}%'.format(s),
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}.get(lookup, lambda s: s)
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converted = value_convert(value)
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sql_bits.append(
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(template.format(column), converted)
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)
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sql_bits.sort(key=lambda p: p[0])
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where_clause = ' and '.join(p[0] for p in sql_bits)
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params = [p[1] for p in sql_bits]
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return where_clause, params
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class CustomJSONEncoder(json.JSONEncoder):
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def default(self, obj):
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if isinstance(obj, sqlite3.Row):
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return tuple(obj)
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if isinstance(obj, sqlite3.Cursor):
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return list(obj)
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if isinstance(obj, bytes):
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# Does it encode to utf8?
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try:
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return obj.decode('utf8')
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except UnicodeDecodeError:
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return {
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'$base64': True,
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'encoded': base64.b64encode(obj).decode('latin1'),
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}
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return json.JSONEncoder.default(self, obj)
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@contextmanager
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def sqlite_timelimit(conn, ms):
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deadline = time.time() + (ms / 1000)
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def handler():
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if time.time() >= deadline:
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return 1
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conn.set_progress_handler(handler, 10000)
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yield
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conn.set_progress_handler(None, 10000)
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def app_factory(files, num_threads=3):
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app = Sanic(__name__)
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jinja = SanicJinja2(
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app,
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loader=FileSystemLoader([
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str(app_root / 'datasite' / 'templates')
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])
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)
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executor = futures.ThreadPoolExecutor(max_workers=num_threads)
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app.add_route(IndexView.as_view(jinja, executor), '/')
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app.add_route(favicon, '/favicon.ico')
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app.add_route(
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DatabaseView.as_view(jinja, executor),
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'/<db_name:[^/\.]+?><as_json:(.jsono?)?$>'
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)
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app.add_route(
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DatabaseDownload.as_view(jinja, executor),
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'/<db_name:[^/]+?><as_db:(\.db)$>'
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)
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app.add_route(
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TableView.as_view(jinja, executor),
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'/<db_name:[^/]+>/<table:[^/]+?><as_json:(.jsono?)?$>'
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)
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app.add_route(
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RowView.as_view(jinja, executor),
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'/<db_name:[^/]+>/<table:[^/]+?>/<pk_path:[^/]+?><as_json:(.jsono?)?$>'
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)
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return app
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