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https://issues.apache.org/jira/browse/HADOOP-13223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15310203#comment-15310203
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john lilley edited comment on HADOOP-13223 at 6/1/16 12:13 PM:
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I think that the problem is something more than winutils.exe... NativeIO only
goes so far in replacing shell commands like chmod and chown, and that's really
the heart of the problem. I think I was taught in college that shelling out to
external commands was a bad idea, and well, now we can see why. I think that a
root resolution of the underlying issues would mean a search-and-replace
mission of shell commands with calls into an enhanced NativeIO. Maybe a
NativeIO that also covers chown? I'm unsure of what shell commands are
actually executed. But of course that in and of itself speaks highly of the
nature of the problem. There is no _interface_ to these operations, so it is a
blind spot of code quality and ability to refactor or analyze.
was (Author: john.lil...@redpoint.net):
I think that the problem is something more than winutils.exe... NativeIO only
goes so far in replacing shell commands like chmod and chown, and that's really
the heart of the problem. I think I was taught in college that shelling out to
external commands was a bad idea, and well, now we can see why. I think that a
root resolution of the underlying issues would mean a search-and-replace
mission of shell commands with calls into an enhanced NativeIO that also covers
chown. But of course that in and of itself speaks highly of the nature of the
problem. There is no _interface_ to these operations, so it is a blind spot of
code quality and ability to refactor or analyze.
> winutils.exe is a bug nexus and should be killed with an axe.
> -------------------------------------------------------------
>
> Key: HADOOP-13223
> URL: https://issues.apache.org/jira/browse/HADOOP-13223
> Project: Hadoop Common
> Issue Type: Improvement
> Components: bin
> Affects Versions: 2.6.0
> Environment: Microsoft Windows, all versions
> Reporter: john lilley
>
> winutils.exe was apparently created as a stopgap measure to allow Hadoop to
> "work" on Windows platforms, because the NativeIO libraries aren't
> implemented there. Rather than building a DLL that makes native OS calls,
> the creators of winutils.exe must have decided that it would be more
> expedient to create an EXE to carry out file system operations in a
> linux-like fashion. Unfortunately, like many stopgap measures in software,
> this one has persisted well beyond its expected lifetime and usefulness. My
> team creates software that runs on Windows and Linux, and winutils.exe is
> probably responsible for 20% of all issues we encounter, both during
> development and in the field.
> Problem #1 with winutils.exe is that it is simply missing from many popular
> distros and/or the client-side software installation for said distros, when
> supplied, fails to install winutils.exe. Thus, as software developers, we
> are forced to pick one version and distribute and install it with our
> software.
> Which leads to problem #2: winutils.exe are not always compatible. In
> particular, MapR MUST have its winutils.exe in the system path, but doing so
> breaks the Hadoop distro for every other Hadoop vendor. This makes creating
> and maintaining test environments that work with all of the Hadoop distros we
> want to test unnecessarily tedious and error-prone.
> Problem #3 is that the mechanism by which you inform the Hadoop client
> software where to find winutils.exe is poorly documented and fragile. First,
> it can be in the PATH. If it is in the PATH, that is where it is found.
> However, the documentation, such as it is, makes no mention of this, and
> instead says that you should set the HADOOP_HOME environment variable, which
> does NOT override the winutils.exe found in your system PATH.
> Which leads to problem #4: There is no logging that says where winutils.exe
> was actually found and loaded. Because of this, fixing problems of finding
> the wrong winutils.exe are extremely difficult.
> Problem #5 is that most of the time, such as when accessing straight up HDFS
> and YARN, one does not *need* winutils.exe. But if it is missing, the log
> messages complain about its absence. When we are trying to diagnose an
> obscure issue in Hadoop (of which there are many), the presence of this red
> herring leads to all sorts of time wasted until someone on the team points
> out that winutils.exe is not the problem, at least not this time.
> Problem #6 is that errors and stack traces from issues involving winutils.exe
> are not helpful. The Java stack trace ends at the ProcessBuilder call. Only
> through bitter experience is one able to connect the dots from
> "ProcessBuilder is the last thing on the stack" to "something is wrong with
> winutils.exe".
> Note that none of these involve running Hadoop on Windows. They are only
> encountered when using Hadoop client libraries to access a cluster from
> Windows.
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