mirror of
https://github.com/trustgraph-ai/trustgraph.git
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2bf4af294e
- Silence pika, cassandra etc. logging at INFO (too much chatter) - Add per processor log tags so that logs can be understood in processor group. - Deal with RabbitMQ lag weirdness - Added more processor group examples
78 lines
2.3 KiB
Python
78 lines
2.3 KiB
Python
"""
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Async wrapper for cassandra-driver sessions.
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The cassandra driver exposes a callback-based async API via
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session.execute_async, returning a ResponseFuture that fires
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on_result / on_error from the driver's own worker thread.
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This module bridges that into an awaitable interface.
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Usage:
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from ..tables.cassandra_async import async_execute
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rows = await async_execute(self.cassandra, stmt, (param1, param2))
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for row in rows:
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...
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Notes:
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- Rows are materialised into a list inside the driver callback
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thread before the future is resolved, so subsequent iteration
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in the caller never triggers a sync page-fetch on the asyncio
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loop. This is safe for single-page results (the common case
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in this codebase); if a query needs pagination, handle it
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explicitly.
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- Callbacks fire on a driver worker thread; call_soon_threadsafe
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is used to hand the result back to the asyncio loop.
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- Errors from the driver are re-raised in the awaiting coroutine.
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"""
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import asyncio
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async def async_execute(session, query, parameters=None):
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"""Execute a CQL statement asynchronously.
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Args:
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session: cassandra.cluster.Session (self.cassandra)
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query: statement string or PreparedStatement
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parameters: tuple/list of bind params, or None
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Returns:
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A list of rows (materialised from the first result page).
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"""
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loop = asyncio.get_running_loop()
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fut = loop.create_future()
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def on_result(rows):
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# Materialise on the driver thread so the loop thread
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# never touches a lazy iterator that might trigger
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# further sync I/O.
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try:
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materialised = list(rows) if rows is not None else []
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except Exception as e:
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loop.call_soon_threadsafe(
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_set_exception_if_pending, fut, e
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)
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return
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loop.call_soon_threadsafe(
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_set_result_if_pending, fut, materialised
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)
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def on_error(exc):
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loop.call_soon_threadsafe(
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_set_exception_if_pending, fut, exc
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)
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rf = session.execute_async(query, parameters)
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rf.add_callbacks(on_result, on_error)
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return await fut
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def _set_result_if_pending(fut, result):
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if not fut.done():
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fut.set_result(result)
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def _set_exception_if_pending(fut, exc):
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if not fut.done():
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fut.set_exception(exc)
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