91 lines
2.3 KiB
Python
91 lines
2.3 KiB
Python
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from collections import deque
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class Transaction:
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"""Filesystem transaction write context
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Gathers files for deferred commit or discard, so that several write
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operations can be finalized semi-atomically. This works by having this
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instance as the ``.transaction`` attribute of the given filesystem
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"""
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def __init__(self, fs, **kwargs):
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"""
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Parameters
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----------
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fs: FileSystem instance
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"""
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self.fs = fs
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self.files = deque()
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def __enter__(self):
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self.start()
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return self
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def __exit__(self, exc_type, exc_val, exc_tb):
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"""End transaction and commit, if exit is not due to exception"""
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# only commit if there was no exception
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self.complete(commit=exc_type is None)
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if self.fs:
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self.fs._intrans = False
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self.fs._transaction = None
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self.fs = None
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def start(self):
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"""Start a transaction on this FileSystem"""
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self.files = deque() # clean up after previous failed completions
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self.fs._intrans = True
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def complete(self, commit=True):
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"""Finish transaction: commit or discard all deferred files"""
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while self.files:
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f = self.files.popleft()
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if commit:
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f.commit()
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else:
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f.discard()
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self.fs._intrans = False
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self.fs._transaction = None
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self.fs = None
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class FileActor:
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def __init__(self):
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self.files = []
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def commit(self):
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for f in self.files:
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f.commit()
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self.files.clear()
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def discard(self):
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for f in self.files:
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f.discard()
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self.files.clear()
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def append(self, f):
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self.files.append(f)
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class DaskTransaction(Transaction):
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def __init__(self, fs):
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"""
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Parameters
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----------
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fs: FileSystem instance
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"""
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import distributed
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super().__init__(fs)
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client = distributed.default_client()
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self.files = client.submit(FileActor, actor=True).result()
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def complete(self, commit=True):
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"""Finish transaction: commit or discard all deferred files"""
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if commit:
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self.files.commit().result()
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else:
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self.files.discard().result()
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self.fs._intrans = False
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self.fs = None
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