xrootd.py

#!/usr/bin/env python

# BSD 3-Clause License; see https://github.com/scikit-hep/uproot/blob/master/LICENSE

from __future__ import absolute_import

import os
import threading

import numpy

import uproot.source.chunked

class XRootDSource(uproot.source.chunked.ChunkedSource):
    # makes __doc__ attribute mutable before Python 3.3
    __metaclass__ = type.__new__(type, "type", (uproot.source.chunked.ChunkedSource.__metaclass__,), {})

    def __init__(self, path, timeout=None, *args, **kwds):
        self._size = None
        self.timeout = timeout
        super(XRootDSource, self).__init__(path, *args, **kwds)

    defaults = {"timeout": None, "chunkbytes": 1024**2, "limitbytes": 100*1024**2, "parallel": False}

    def _open(self):
        try:
            os.environ["XRD_RUNFORKHANDLER"] = "1"   # To make uproot + xrootd + multiprocessing work
            import pyxrootd.client
        except ImportError:
            raise ImportError("Install pyxrootd package with:\n    conda install -c conda-forge xrootd\n(or download from http://xrootd.org/dload.html and manually compile with cmake; setting PYTHONPATH and LD_LIBRARY_PATH appropriately).")

        if self._source is None or not self._source.is_open():
            self._source = pyxrootd.client.File()
            status, dummy = self._source.open(self.path, timeout=(0 if self.timeout is None else self.timeout))
            if status.get("error", None):
                raise OSError(status["message"])
            status, info = self._source.stat(timeout=(0 if self.timeout is None else self.timeout))
            if status.get("error", None):
                raise OSError(status["message"])
            self._size = info["size"]

    def size(self):
        if self._size is None:
            self._open()
        return self._size

    def threadlocal(self):
        out = XRootDSource.__new__(self.__class__)
        out.path = self.path
        out._chunkbytes = self._chunkbytes
        out.cache = self.cache
        out._source = None             # XRootD connections are *not shared* among threads
        out._size = self._size
        out.timeout = self.timeout
        out._parallel = self._parallel
        out._executor = None
        out._futures = {}
        return out

    def _read(self, chunkindex):
        self._open()
        status, data = self._source.read(int(chunkindex * self._chunkbytes), int(self._chunkbytes), timeout=int(0 if self.timeout is None else self.timeout))
        if status.get("error", None):
            raise OSError(status["message"])
        return numpy.frombuffer(data, dtype=numpy.uint8)

    def _setup_futures(self, parallel):
        self._parallel = parallel
        self._executor = None
        self._futures = {}

    class _preload(object):
        def __init__(self, timeout):
            self.timeout = timeout
            self.out = None
            self.hold = threading.Event()

        def __call__(self, status, data, hostlist):
            if not status.get("error", None):
                self.out = numpy.frombuffer(data, dtype=numpy.uint8)
            self.hold.set()

        def result(self):
            if self.hold.wait(self.timeout):
                return self.out

    def preload(self, starts):
        if self._parallel:
            self._open()
            limitnum = self._limitbytes // self._chunkbytes
            timeout = int(0 if self.timeout is None else self.timeout)
            for start in starts:
                if len(self._futures) > limitnum:
                    break
                chunkindex = start // self._chunkbytes
                try:
                    self.cache[chunkindex]
                except KeyError:
                    callback = self._preload(timeout)
                    status = self._source.read(int(chunkindex * self._chunkbytes), int(self._chunkbytes), timeout=timeout, callback=callback)
                    if status["ok"]:
                        self._futures[chunkindex] = callback

    def __del__(self):
        if self._source is not None:
            self._source.close(timeout=(0 if self.timeout is None else self.timeout))

    def dismiss(self):
        self._futures = {}