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From "Timothy Chen" <tnac...@apache.org>
Subject Re: Review Request 30774: Fetcher Cache
Date Fri, 06 Mar 2015 22:15:28 GMT

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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/30774/#review75491
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include/mesos/fetcher/fetcher.proto
<https://reviews.apache.org/r/30774/#comment122581>

    It's harder to make a optional field required, but it's much easier the other way around.
    
    If we always want it to be required, I think we should make the sandbox a required field.



src/hdfs/hdfs.hpp
<https://reviews.apache.org/r/30774/#comment122582>

    IMO this should be in another patch and we can get this commited right away.



src/launcher/fetcher.cpp
<https://reviews.apache.org/r/30774/#comment122584>

    Why not log the error if it's there? available.error()



src/launcher/fetcher.cpp
<https://reviews.apache.org/r/30774/#comment122585>

    You log the extraction command but in this case don't log the copy command.
    
    I think to be consistent, let's not log the command, and like you do here only log when
the command fails.
    
    What you think?



src/launcher/fetcher.cpp
<https://reviews.apache.org/r/30774/#comment122591>

    Failed to chmod executable



src/launcher/fetcher.cpp
<https://reviews.apache.org/r/30774/#comment122597>

    CHECK_EQ(item.action(), FetcherInfo::Item::DOWNLOAD_AND_CACHE)



src/slave/containerizer/fetcher.hpp
<https://reviews.apache.org/r/30774/#comment122598>

    Are these static methods going to be used somewhere else? Quite a lot of static methods
now in the header and perhaps we just need to put the implementation in the cpp file, BenH
also mentioned this last time in the review meeting.



src/slave/containerizer/fetcher.hpp
<https://reviews.apache.org/r/30774/#comment122601>

    I think there is a bit of complication with this interface, where a user has to call two
things at the end of a downloading from an Entry:
    
    - unreference
    - complete/fail
    
    And I don't see how one ever wants to use them without each other.
    
    Why not hide unreference all together, and decrement the reference count in complete or
fail?
    
    This way it's a lot less error prone, and harder to make mistakes with future changes.



src/slave/containerizer/fetcher.hpp
<https://reviews.apache.org/r/30774/#comment122732>

    Why not just store the Path and return that?



src/slave/containerizer/fetcher.hpp
<https://reviews.apache.org/r/30774/#comment122731>

    Where is this being used?



src/slave/containerizer/fetcher.cpp
<https://reviews.apache.org/r/30774/#comment122588>

    Let's use strings::contains instead of find to be consistent here.



src/slave/containerizer/fetcher.cpp
<https://reviews.apache.org/r/30774/#comment122736>

    What's the point of this empty branch?



src/slave/containerizer/fetcher.cpp
<https://reviews.apache.org/r/30774/#comment122738>

    This seems to be very easy to make mistakes with setSpace, especially when it's not even
expected to be called more than once? 
    
    I thought you said you're going to change it so it's only set once during initialization?



src/slave/containerizer/fetcher.cpp
<https://reviews.apache.org/r/30774/#comment122733>

    We should be more explicit here, that we're claiming more than the space we've set to.



src/slave/containerizer/fetcher.cpp
<https://reviews.apache.org/r/30774/#comment122734>

    Add some message?



src/slave/containerizer/fetcher.cpp
<https://reviews.apache.org/r/30774/#comment122735>

    Add some message?



src/slave/slave.cpp
<https://reviews.apache.org/r/30774/#comment122730>

    Why is this just a Failure but the other recover is a LOG(FATAL)? Shouldn't we exit here
too if unable to recover cache is a critical event?



src/tests/mesos.hpp
<https://reviews.apache.org/r/30774/#comment122578>

    We want to have a consistent naming style across all the tests and files, and we usually
in all the tests in Mesos, the "unmocked" methods tend to just have a prefix of "_", so run
-> _run


- Timothy Chen


On March 6, 2015, 1:46 p.m., Bernd Mathiske wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/30774/
> -----------------------------------------------------------
> 
> (Updated March 6, 2015, 1:46 p.m.)
> 
> 
> Review request for mesos, Adam B, Benjamin Hindman, Till Toenshoff, and Timothy Chen.
> 
> 
> Bugs: MESOS-2057, MESOS-2069, MESOS-2070, MESOS-2072, MESOS-2073, and MESOS-2074
>     https://issues.apache.org/jira/browse/MESOS-2057
>     https://issues.apache.org/jira/browse/MESOS-2069
>     https://issues.apache.org/jira/browse/MESOS-2070
>     https://issues.apache.org/jira/browse/MESOS-2072
>     https://issues.apache.org/jira/browse/MESOS-2073
>     https://issues.apache.org/jira/browse/MESOS-2074
> 
> 
> Repository: mesos
> 
> 
> Description
> -------
> 
> Almost all of the functionality in epic MESOS-336. Downloaded files from CommandInfo::URIs
can now be cached in a cache directory designated by a slave flag. This only happens when
asked for by an extra flag in the URI and is thus backwards-compatible. The cache has a size
limit also given by a new slave flag. Cache-resident files are evicted as necessary to make
space for newly fetched ones. Concurrent attempts to cache the same URI leads to only one
download. The fetcher program remains external for safety reasons, but is now augmented with
more elaborate parameters packed into a JSON object to implement specific fetch actions for
all of the above. Additional testing includes fetching from (mock) HDFS and coverage of the
new features.
> 
> 
> Diffs
> -----
> 
>   docs/fetcher-cache-internals.md PRE-CREATION 
>   docs/fetcher.md PRE-CREATION 
>   include/mesos/fetcher/fetcher.proto 311af9aebc6a85dadba9dbeffcf7036b70896bcc 
>   include/mesos/mesos.proto 9df972d750ce1e4a81d2e96cc508d6f83cad2fc8 
>   src/Makefile.am d299f07d865080676ca8a550cf6005c6ab32839f 
>   src/hdfs/hdfs.hpp 968545d9af896f3e72e156484cc58135405cef6b 
>   src/launcher/fetcher.cpp 796526f59c25898ef6db2b828b0e2bb7b172ba25 
>   src/slave/constants.hpp fd1c1aba0aa62372ab399bee5709ce81b8e92cec 
>   src/slave/containerizer/docker.hpp b7bf54ac65d6c61622e485ac253513eaac2e4f88 
>   src/slave/containerizer/docker.cpp 5f4b4ce49a9523e4743e5c79da4050e6f9e29ed7 
>   src/slave/containerizer/fetcher.hpp 1db0eaf002c8d0eaf4e0391858e61e0912b35829 
>   src/slave/containerizer/fetcher.cpp 9e9e9d0eb6b0801d53dec3baea32a4cd4acdd5e2 
>   src/slave/containerizer/mesos/containerizer.hpp ae61a0fcd19f2ba808624312401f020121baf5d4

>   src/slave/containerizer/mesos/containerizer.cpp ec4626f903d44c0911093ff763ef16ad27c418a9

>   src/slave/flags.hpp 56b25caf3901b38bdecb50310e8bcae0b114efa8 
>   src/slave/slave.cpp a06d68032f26ccb3f786b6ea7c3a6c3c52449bd2 
>   src/tests/docker_containerizer_tests.cpp 06cd3d89ecbaaac17ae6970604b21fbe29f6e887 
>   src/tests/fetcher_cache_tests.cpp PRE-CREATION 
>   src/tests/fetcher_tests.cpp 4549e6a631e2c17cec3766efaa556593eeac9a1e 
>   src/tests/mesos.hpp e91e5e484eea4587ac8f2eb9cefeab4acc9f4615 
>   src/tests/mesos.cpp c8f43d21b214e75eaac2870cbdf4f03fd18707d1 
> 
> Diff: https://reviews.apache.org/r/30774/diff/
> 
> 
> Testing
> -------
> 
> make check
> 
> --- longer Description: ---
> 
> -Replaces all other reviews for the fetcher cache except those related to stout: 30006,
30033, 30034, 30036, 30037, 30039, 30124, 30173, 30614, 30616, 30618, 30621, 30626. See descriptions
of those. In dependency order:
> 
> 30033: Removes the fetcher env tests since these won't be needed any more when the fetcher
uses JSON in a single env var as a parameter. They never tested anything that won't be covered
by other tests anyway.
> 
> 30034: Makes the code structure of all fetcher tests the same. Instead of calling the
run method of the fetcher directly, calling through fetch(). Also removes all uses of I/O
redirection, which is not really needed for debugging, and thus the next patch can refactor
fetch() and run(). (The latter comes in two varieties, which complicates matters without much
benefit.)
> 
> 30036: Extends the CommandInfo::URI protobuf with a boolean "caching" field that will
later cause fetcher cache actions. Also introduces the notion of a cache directory to the
fetcher info protobuf. And then propagates these additions throughout the rest of the code
base where applicable. This includes passing the slave ID all the way down to the place where
the cache dir name is constructed.
> 
> 30037: Extends the fetcher info protobuf with "actions" (fetch directly bypassing the
cache, fetch through the cache, retrieve from the cache). Switches the basis for dealing with
uris to "items", which contain the uri, the action, and potentially a cache file name. Refactors
fetch() and run(), so there is only one of each. Introduces about half of the actual cache
logic, including a hashmap of cache file objects for bookkeeping and basic operations on it.

> 
> 30039: Enables fetcher cache actions in the mesos fetcher program.
> 
> 30006: Enables concurrent downloading into the fetcher cache. Reuse of download results
in the cache when multiple fetcher runs occur concurrently. 
> 
> 30614: This is to ensure that all this refactoring of fetcher code has not broken HDFS
fetching. Adds a test that exercises the C++ code paths in Mesos and mesos-fetcher related
to fetching from HDFS. Uses a mock HDFS client written in bash that acts just like a real
"hadoop" command if used in the right limited way.
> 
> 30124: Inserted fetcher cache zap upon slave startup, recovery and shutdown. This implements
recovery in an acceptable, yet most simple way.
> 
> 30173: Created fetcher cache tests. Adds a new test source file containing a test fixture
and tests to find out if the fetcher cache works with a variety of settings.
> 
> 30616: Adds hdfs::du() which calls "hadoop fs -du -h" and returns a string that contains
the file size for the URI passed as argument. This is needed to determine the size of a file
on HDFS before downloading it to the fetcher cache (to ensure there is enough space).
> 
> 30621: Refactored URI type separation in mesos-fetcher. Moved the URI type separation
code (distinguishes http, hdfs, local copying, etc.) from mesos-fetcher to the fetcher process/actor,
since it is going to be reused by download size queries when we introduce fetcher cache management.
Also factored out URI validation, which will be used the same way by mesos-fetcher and the
fetcher process/actor.
> 
> 30626: Fetcher cache eviction. This happens when the cache does not have enough space
to accomodate upcoming downloads to the cache. Necessary provisions included here:
> - mesos-fetcher does not run until evictions have been successful
> - Cache space is reserved while (async) waiting for eviction to succeed. If it fails,
the reservation gets undone.
> - Reservations can be partly from available space, partly from evictions. All math included
:-)
> - To find out how much space is needed, downloading has a prelude in which we query the
download size from the URI. This works for all URI types that mesos-fetcher currently supports,
including http and hdfs.
> - Size-determination requests are now synchronized, too. Only one per URI in play happens.
> - There is cleanup code for all kinds of error situations. At the very end of the fetch
attempt, each list is processed for undoing things like space reservations and eviction disabling.
> - Eviction gets disabled for URIs that are currently in use, i.e. the related cache files
are. We use reference counting for this, since there may be concurrent fetch attempts using
the same cache files.
> 
> 
> Thanks,
> 
> Bernd Mathiske
> 
>


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