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https://issues.apache.org/jira/browse/BEAM-6027?focusedWorklogId=247495&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-247495
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ASF GitHub Bot logged work on BEAM-6027:
----------------------------------------
Author: ASF GitHub Bot
Created on: 23/May/19 15:53
Start Date: 23/May/19 15:53
Worklog Time Spent: 10m
Work Description: chamikaramj commented on issue #8553: [BEAM-6027] Fix
slow downloads when reading from GCS
URL: https://github.com/apache/beam/pull/8553#issuecomment-495277810
Thanks for the update. This looks great.
Seems like the file you used for your microbenchmark is about 4MB which will
be within the first chunk for the new buffer size. Can you try running a Beam
pipeline with a larger input (say 10GB) with Dataflow to confirm that there's
no regression at large scale ?
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Issue Time Tracking
-------------------
Worklog Id: (was: 247495)
Time Spent: 50m (was: 40m)
> Slow DownloaderStream when reading from GCS
> -------------------------------------------
>
> Key: BEAM-6027
> URL: https://issues.apache.org/jira/browse/BEAM-6027
> Project: Beam
> Issue Type: Bug
> Components: sdk-py-core
> Reporter: Andreas Jansson
> Priority: Minor
> Time Spent: 50m
> Remaining Estimate: 0h
>
> DownloaderStream inherits io.RawIOBase, which by defaults reads
> io.DEFAULT_BUFFER_SIZE chunks in .readall(). This is causing extremely slow
> performance when invoking read() on handles returned by GcsIO().open().
> The following code can take ~60 seconds to download a single 2MB file:
> {code:python}
> gcs = GcsIO()
> t = time.time()
> path = 'gs://my-bucket/my-2MB-file'
> with gcs.open(path) as f:
> f.read()
> duration = time.time() - t
> {code}
> This monkey patch makes the same download code take <1 second:
> {code:python}
> from apache_beam.io.gcp import gcsio
> from apache_beam.io.filesystemio import DownloaderStream
> def downloader_stream_readall(self):
> """Read until EOF, using multiple read() call."""
> res = bytearray()
> while True:
> data = self.read(gcsio.DEFAULT_READ_BUFFER_SIZE)
> if not data:
> break
> res += data
> if res:
> return bytes(res)
> else:
> return data
> DownloaderStream.readall = downloader_stream_readall
> {code}
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