提交 fbd1d1cf 编写于 作者: T typhoonzero

refine pipe_reader

上级 af0c4c45
...@@ -334,93 +334,72 @@ def _buf2lines(buf, line_break="\n"): ...@@ -334,93 +334,72 @@ def _buf2lines(buf, line_break="\n"):
return lines[:-1], lines[-1] return lines[:-1], lines[-1]
def pipe_reader(left_cmd, class PipeReader:
parser,
bufsize=8192,
file_type="plain",
cut_lines=True,
line_break="\n"):
""" """
pipe_reader read data by stream from a command, take it's PipeReader read data by stream from a command, take it's
stdout into a pipe buffer and redirect it to the parser to stdout into a pipe buffer and redirect it to the parser to
parse, then yield data as your desired format. parse, then yield data as your desired format.
You can using standard linux command or call another program You can using standard linux command or call another program
to read data, from HDFS, Ceph, URL, AWS S3 etc: to read data, from HDFS, Ceph, URL, AWS S3 etc:
cmd = "hadoop fs -cat /path/to/some/file" .. code-block:: python
cmd = "cat sample_file.tar.gz" cmd = "hadoop fs -cat /path/to/some/file"
cmd = "curl http://someurl" cmd = "cat sample_file.tar.gz"
cmd = "python print_s3_bucket.py" cmd = "curl http://someurl"
cmd = "python print_s3_bucket.py"
A sample parser: An example:
.. code-block:: python
def sample_parser(lines): def example_reader():
# parse each line as one sample data, for f in myfiles:
# return a list of samples as batches. pr = PipeReader("cat %s"%f)
ret = [] for l in pr.get_line():
for l in lines: sample = l.split(" ")
ret.append(l.split(" ")[1:5]) yield sample
return ret
:param left_cmd: command to excute to get stdout from.
:type left_cmd: string
:param parser: parser function to parse lines of data.
if cut_lines is True, parser will receive list
of lines.
if cut_lines is False, parser will receive a
raw buffer each time.
parser should return a list of parsed values.
:type parser: callable
:param bufsize: the buffer size used for the stdout pipe.
:type bufsize: int
:param file_type: can be plain/gzip, stream buffer data type.
:type file_type: string
:param cut_lines: whether to pass lines instead of raw buffer
to the parser
:type cut_lines: bool
:param line_break: line break of the file, like \n or \r
:type line_break: string
:return: the reader generator.
:rtype: callable
""" """
if not isinstance(left_cmd, str):
raise TypeError("left_cmd must be a string")
if not callable(parser):
raise TypeError("parser must be a callable object")
# TODO(typhoonzero): add a thread to read stderr
# Always init a decompress object is better than
# create in the loop.
dec = zlib.decompressobj(
32 + zlib.MAX_WBITS) # offset 32 to skip the header
def reader(): def __init__(self, command, bufsize=8192, file_type="plain"):
process = subprocess.Popen( if not isinstance(command, str):
left_cmd.split(" "), bufsize=bufsize, stdout=subprocess.PIPE) raise TypeError("left_cmd must be a string")
if file_type == "gzip":
self.dec = zlib.decompressobj(
32 + zlib.MAX_WBITS) # offset 32 to skip the header
self.file_type = file_type
self.bufsize = bufsize
self.process = subprocess.Popen(
command.split(" "), bufsize=bufsize, stdout=subprocess.PIPE)
def get_line(self, cut_lines=True, line_break="\n"):
"""
:param cut_lines: cut buffer to lines
:type cut_lines: bool
:param line_break: line break of the file, like \n or \r
:type line_break: string
:return: one line or a buffer of bytes
:rtype: string
"""
remained = "" remained = ""
while True: while True:
buff = process.stdout.read(bufsize) buff = self.process.stdout.read(self.bufsize)
if buff: if buff:
if file_type == "gzip": if self.file_type == "gzip":
decomp_buff = dec.decompress(buff) decomp_buff = self.dec.decompress(buff)
elif file_type == "plain": elif self.file_type == "plain":
decomp_buff = buff decomp_buff = buff
else: else:
raise TypeError("file_type %s is not allowed" % file_type) raise TypeError("file_type %s is not allowed" %
self.file_type)
if cut_lines: if cut_lines:
lines, remained = _buf2lines(''.join( lines, remained = _buf2lines(''.join(
[remained, decomp_buff]), line_break) [remained, decomp_buff]), line_break)
parsed_list = parser(lines) for line in lines:
for ret in parsed_list: yield line
yield ret
else: else:
for ret in parser(decomp_buff): yield decomp_buff
yield ret
else: else:
break break
return reader
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