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From Aaron McCurry <amccu...@gmail.com>
Subject Re: Index Warmup in Blur
Date Fri, 11 Oct 2013 00:37:19 GMT
On Wed, Oct 9, 2013 at 1:57 AM, Ravikumar Govindarajan <
ravikumar.govindarajan@gmail.com> wrote:

> Yes, I think bringing in a mutable file in lucene-index brings it's own set
> of problems to handle. Filters, Caches, Scoring, Snapshots/Commits etc...
> will all be affected.
>
> There is on JIRA on writing generation of updatable files, just like
> doc-deletes instead of over-writing a single file.[
> https://issues.apache.org/jira/browse/LUCENE-4258]. But that is still
> in-progress and from what I understand, it could slow searches
> considerably.
>

I think that we can add whatever api extension point that are necessary to
have users modify anything.  However I the more I think about things the
more I think that there are too many rules built on immutability.  Block
cache, HDFS, filters, search cache, etc.


>
> BTW, is it possible to extend BlurPartitioner and load it during start-up?
>

Not yet, but anything is just a patch away.  :-)


>
> Also, it would be awesome if Blur supports a per-row auto-complete feature.
>

Not sure what you mean.  Are you talking about in the shell?

Aaron


>
> --
> Ravi
>
>
> On Sat, Oct 5, 2013 at 2:01 AM, Aaron McCurry <amccurry@gmail.com> wrote:
>
> > I have thought of one possible problem with this approach.  To date the
> > mindset I have used in all of the Blur internals is that segments are
> > immutable.  This is a fundamental principle that Blur uses and I don't
> > really have any ideas on where to behind checking for when this is a
> > problem.  I know filters are going to be an issue, not sure where else.
> >
> > Not saying that it can't be done, it's just not going to be as clean as I
> > originally thought.
> >
> > Aaron
> >
> >
> > On Fri, Oct 4, 2013 at 4:26 PM, Aaron McCurry <amccurry@gmail.com>
> wrote:
> >
> > >
> > >
> > > On Fri, Oct 4, 2013 at 7:15 AM, Ravikumar Govindarajan <
> > > ravikumar.govindarajan@gmail.com> wrote:
> > >
> > >> On a related note, do you think such an approach will fit in Blur
> > >>
> > >> 1. Store the BDB file in shard-server itself.
> > >>
> > >
> > > Probably not, this would pin the BDB (or whatever the solution would
> be)
> > > to a specific server.  We will have to sync to HDFS.
> > >
> > >
> > >>
> > >> 2. Apply all incoming partial doc-updates to local BDB file as well as
> > an
> > >>     update-transaction log
> > >>
> > >
> > > Blur already has a write ahead log as apart of internals.  It's written
> > > and synced to HDFS.
> > >
> > >
> > >>
> > >> 3. Periodically sync dirty BDB files to HDFS and roll-over the update-
> > >>  transaction log.
> > >
> > >
> > >> Whenever a shard-server goes down, the take-over server can initially
> > sync
> > >> the BDB file from HDFS to local, replay the update-transaction log and
> > >> then
> > >> start serving data
> > >>
> > >
> > > Blur already does this internally, it records the mutates and replays
> > them
> > > if a failure happens before a commit.
> > >
> > > Aaron
> > >
> > >
> > >>
> > >> --
> > >> Ravi
> > >>
> > >>
> > >> On Thu, Oct 3, 2013 at 11:14 PM, Ravikumar Govindarajan <
> > >> ravikumar.govindarajan@gmail.com> wrote:
> > >>
> > >> > The mutate APIs are a good fit for individual cols update. BlurCodec
> > >> will
> > >> > be cool and solve a lot of problems.
> > >> >
> > >> > There are 3 caveats for such a codec
> > >> >
> > >> > 1. Scores for affected queries will be wrong, until segment-merge
> > >> >
> > >> > 2. Responsibility of ordering updates must be on the client.
> > >> >
> > >> > 3. Repeated updates for the same document can either take a
> > generational
> > >> > approach [Lucene-4258] or use a single version of storage [Redis/TC
> > >> etc..],
> > >> > pushing the onus to client, depending on how the Codec shapes up.
> > >> >
> > >> > The former will be semantically correct but really sluggish while
> the
> > >> > latter will be faster during search
> > >> >
> > >> >
> > >> >
> > >> > On Thu, Oct 3, 2013 at 8:53 PM, Aaron McCurry <amccurry@gmail.com>
> > >> wrote:
> > >> >
> > >> >> On Thu, Oct 3, 2013 at 11:08 AM, Ravikumar Govindarajan <
> > >> >> ravikumar.govindarajan@gmail.com> wrote:
> > >> >>
> > >> >> > Yeah, you are correct. A BDB file might probably never be
ported
> to
> > >> >> HDFS.
> > >> >> >
> > >> >> > Our daily update frequency comes to about 20% of insertion
rate.
> > >> >> >
> > >> >> > Lets say "UPDATE <TABLE> SET COL2=1 WHERE COL1=X".
> > >> >> >
> > >> >> > This update could potentially span across tens of thousands
of
> SQL
> > >> rows
> > >> >> in
> > >> >> > our case, where COL2 is just a boolean flip.
> > >> >> >
> > >> >> > The problem is not with lucene's ability to handle load.
Instead
> it
> > >> is
> > >> >> with
> > >> >> > the consistent load it puts on our content servers to read
and
> > >> >> re-tokenize
> > >> >> > such huge rows just for a boolean flip. Another big winner
is
> that
> > >> all
> > >> >> our
> > >> >> > updatable fields are not involved in scoring at all. Just
> matching
> > >> will
> > >> >> do.
> > >> >> >
> > >> >> > The changes also sit in BDB only till the next segment merge,
> after
> > >> >> which
> > >> >> > it is cleaned out. There is very little perf hit here for
us, as
> > >> users
> > >> >> > don't immediately search after a change.
> > >> >> >
> > >> >> > I am afraid there is no documentation/code/numbers on this
> > currently
> > >> in
> > >> >> > public, as it is still proprietary but is remarkably similar
to
> the
> > >> >> popular
> > >> >> > to RedisCodec.
> > >> >> >
> > >> >> > "If you really need partial document updates, there would
need to
> > be
> > >> >> > changes
> > >> >> > throughout the entire stack"
> > >> >> >
> > >> >> > You mean, the entire stack of Blur? In case this is possible,
can
> > you
> > >> >> give
> > >> >> > me 10000-ft overview of what you have in mind?
> > >> >> >
> > >> >>
> > >> >> Interesting, now that I think about it.  The situation that you
> > >> describe
> > >> >> is
> > >> >> very interesting, I'm wondering if we came up with something like
> > this
> > >> in
> > >> >> Blur that it would fix our large Row issue.  Or at the very least
> > help
> > >> the
> > >> >> problem.
> > >> >>
> > >> >> https://issues.apache.org/jira/browse/BLUR-220
> > >> >>
> > >> >> Plus the more I think about it, the mutate methods are probably
the
> > >> right
> > >> >> implementation for modifying single columns.  So the API of Blur
> > >> probably
> > >> >> wouldn't need to be changed.  Maybe just the way it goes about
> > dealing
> > >> >> with
> > >> >> changes.  I thinking maybe we need our own BlurCodec to handle
> large
> > >> Rows
> > >> >> as well as Record (Document) updates.
> > >> >>
> > >> >> As an aside I constantly am having to refer to Records as
> Documents,
> > >> this
> > >> >> is why I think we need a rename.
> > >> >>
> > >> >> Aaron
> > >> >>
> > >> >>
> > >> >>
> > >> >>
> > >> >>
> > >> >>
> > >> >> >
> > >> >> > --
> > >> >> > Ravi
> > >> >> >
> > >> >> >
> > >> >> > On Thu, Oct 3, 2013 at 5:36 PM, Aaron McCurry <
> amccurry@gmail.com>
> > >> >> wrote:
> > >> >> >
> > >> >> > > The biggest issue with this is that the shards (the
indexes)
> > >> inside of
> > >> >> > Blur
> > >> >> > > actually move from one server to another.  So to support
this
> > >> behavior
> > >> >> > all
> > >> >> > > the indexes are stored in HDFS.  Do due the differences
between
> > >> HDFS
> > >> >> and
> > >> >> > > the a normal POSIX file system, I highly doubt that
the BDB
> file
> > >> form
> > >> >> in
> > >> >> > > TokyoCabinet can ever be supported.
> > >> >> > >
> > >> >> > > If you really need partial document updates, there would
need
> to
> > be
> > >> >> > changes
> > >> >> > > throughout the entire stack.  I am curious why you need
this
> > >> feature?
> > >> >>  Do
> > >> >> > > you have that many updates to the index?  What is the
update
> > >> >> frequency?
> > >> >> > >  I'm just curious of what kind of performance you get
out of a
> > >> setup
> > >> >> like
> > >> >> > > that?  Since I haven't ever run such a setup I have
no idea how
> > to
> > >> >> > compare
> > >> >> > > that kind of system to a base Lucene setup.
> > >> >> > >
> > >> >> > > Could you point be to some code or documentation?  I
would to
> go
> > >> and
> > >> >> > take a
> > >> >> > > look.
> > >> >> > >
> > >> >> > > Thanks,
> > >> >> > > Aaron
> > >> >> > >
> > >> >> > >
> > >> >> > >
> > >> >> > > On Thu, Oct 3, 2013 at 7:00 AM, Ravikumar Govindarajan
<
> > >> >> > > ravikumar.govindarajan@gmail.com> wrote:
> > >> >> > >
> > >> >> > > > One more help.
> > >> >> > > >
> > >> >> > > > We also maintain a file by name "BDB", just like
the "Sample"
> > >> file
> > >> >> for
> > >> >> > > > tracing used by Blur.
> > >> >> > > >
> > >> >> > > > This "BDB" file pertains to TokyoCabinet and is
used purely
> for
> > >> >> > > supporting
> > >> >> > > > partial updates to a document.
> > >> >> > > > All operations on this file rely on local file-paths
only,
> > >> through
> > >> >> the
> > >> >> > > use
> > >> >> > > > of native code.
> > >> >> > > > Currently, all update requests are local to the
index files
> and
> > >> it
> > >> >> > > becomes
> > >> >> > > > trivial to support.
> > >> >> > > >
> > >> >> > > > Any pointers on how to take this forward in Blur
set-up of
> > >> >> > shard-servers
> > >> >> > > &
> > >> >> > > > controllers?
> > >> >> > > >
> > >> >> > > > --
> > >> >> > > > Ravi
> > >> >> > > >
> > >> >> > > >
> > >> >> > > > On Tue, Oct 1, 2013 at 10:15 PM, Aaron McCurry
<
> > >> amccurry@gmail.com>
> > >> >> > > wrote:
> > >> >> > > >
> > >> >> > > > > You can control the fields to warmup via:
> > >> >> > > > >
> > >> >> > > > >
> > >> >> > > > >
> > >> >> > > >
> > >> >> > >
> > >> >> >
> > >> >>
> > >>
> >
> http://incubator.apache.org/blur/docs/0.2.0/Blur.html#Struct_TableDescriptor
> > >> >> > > > >
> > >> >> > > > > The preCacheCols field.  The comment is wrong
however, so I
> > >> will
> > >> >> > > create a
> > >> >> > > > > task to correct.  The use of the field is:
"family.column"
> > just
> > >> >> like
> > >> >> > > you
> > >> >> > > > > would search.
> > >> >> > > > >
> > >> >> > > > > Aaron
> > >> >> > > > >
> > >> >> > > > >
> > >> >> > > > > On Tue, Oct 1, 2013 at 12:41 PM, Ravikumar
Govindarajan <
> > >> >> > > > > ravikumar.govindarajan@gmail.com> wrote:
> > >> >> > > > >
> > >> >> > > > > > Thanks Aaron
> > >> >> > > > > >
> > >> >> > > > > > General sampling and warming is fine
and the code is
> really
> > >> >> concise
> > >> >> > > and
> > >> >> > > > > > clear.
> > >> >> > > > > >
> > >> >> > > > > >  The act of reading
> > >> >> > > > > > brings the data into the block cache
and the result is
> that
> > >> the
> > >> >> > index
> > >> >> > > > is
> > >> >> > > > > > "hot".
> > >> >> > > > > >
> > >> >> > > > > > Will all the terms of a field be read
and brought into
> the
> > >> >> cache?
> > >> >> > If
> > >> >> > > > so,
> > >> >> > > > > > then it has an obvious implication to
avoid fields like,
> > say
> > >> >> > > > > > attachment-data from warming up, provided
queries don't
> > often
> > >> >> > include
> > >> >> > > > > such
> > >> >> > > > > > fields
> > >> >> > > > > >
> > >> >> > > > > >
> > >> >> > > > > > On Tue, Oct 1, 2013 at 7:58 PM, Aaron
McCurry <
> > >> >> amccurry@gmail.com>
> > >> >> > > > > wrote:
> > >> >> > > > > >
> > >> >> > > > > > > Take a look at this package.
> > >> >> > > > > > >
> > >> >> > > > > > >
> > >> >> > > > > > >
> > >> >> > > > > >
> > >> >> > > > >
> > >> >> > > >
> > >> >> > >
> > >> >> >
> > >> >>
> > >>
> >
> https://git-wip-us.apache.org/repos/asf?p=incubator-blur.git;a=tree;f=blur-store/src/main/java/org/apache/blur/lucene/warmup;h=f4239b1947965dc7fe8218eaa16e3f39ecffdda0;hb=apache-blur-0.2
> > >> >> > > > > > >
> > >> >> > > > > > > Basically when the warmup process
starts (which is
> > >> >> asynchronous
> > >> >> > to
> > >> >> > > > the
> > >> >> > > > > > rest
> > >> >> > > > > > > of the application) it flips a thread
local switch to
> > allow
> > >> >> for
> > >> >> > > > tracing
> > >> >> > > > > > of
> > >> >> > > > > > > the file accesses.  The sampler
will sample each of the
> > >> >> fields in
> > >> >> > > > each
> > >> >> > > > > > > segment and create a sample file
that attempts to
> detect
> > >> the
> > >> >> > > > boundaries
> > >> >> > > > > > of
> > >> >> > > > > > > each field within each file within
each segment.  Then
> it
> > >> >> stores
> > >> >> > > the
> > >> >> > > > > > sample
> > >> >> > > > > > > info into the directory beside each
segment (so that
> way
> > it
> > >> >> > doesn't
> > >> >> > > > > have
> > >> >> > > > > > to
> > >> >> > > > > > > re-sample the segment).  After the
sampling is complete
> > or
> > >> >> > loaded,
> > >> >> > > > the
> > >> >> > > > > > > warmup just reads the binary data
from each file.  The
> > act
> > >> of
> > >> >> > > reading
> > >> >> > > > > > > brings the data into the block cache
and the result is
> > that
> > >> >> the
> > >> >> > > index
> > >> >> > > > > is
> > >> >> > > > > > > "hot".
> > >> >> > > > > > >
> > >> >> > > > > > > Hope this helps.
> > >> >> > > > > > >
> > >> >> > > > > > > Aaron
> > >> >> > > > > > >
> > >> >> > > > > > >
> > >> >> > > > > > >
> > >> >> > > > > > >
> > >> >> > > > > > > On Tue, Oct 1, 2013 at 10:09 AM,
Ravikumar
> Govindarajan <
> > >> >> > > > > > > ravikumar.govindarajan@gmail.com>
wrote:
> > >> >> > > > > > >
> > >> >> > > > > > > > As I understand,
> > >> >> > > > > > > >
> > >> >> > > > > > > > Lucene will store the files
in following way
> > per-segment
> > >> >> > > > > > > >
> > >> >> > > > > > > > TIM file
> > >> >> > > > > > > >      Field1 ---> Some byte[]
> > >> >> > > > > > > >      Field2 ---> Some byte[]
> > >> >> > > > > > > >
> > >> >> > > > > > > > TIP file
> > >> >> > > > > > > >      Field1 ---> Some byte[]
> > >> >> > > > > > > >      Field2 ---> Some byte[]
> > >> >> > > > > > > >
> > >> >> > > > > > > >
> > >> >> > > > > > > > Blur will "sample" this lucene-file
in the following
> > way
> > >> >> > > > > > > >
> > >> >> > > > > > > > Field1 --> <TIM, start-offset>,
<TIP, start-offset>,
> > ...
> > >> >> > > > > > > >
> > >> >> > > > > > > > Field 2 --> <TIM, start-offset>,
<TIP, start-offset>,
> > ...
> > >> >> > > > > > > >
> > >> >> > > > > > > > Is my understanding correct?
> > >> >> > > > > > > >
> > >> >> > > > > > > > How does Blur warm-up the fields,
when it does not
> know
> > >> the
> > >> >> > > > > > "end-offset"
> > >> >> > > > > > > or
> > >> >> > > > > > > > the "length" for each field
to warm.
> > >> >> > > > > > > >
> > >> >> > > > > > > > Will it by default read all
Terms of a field?
> > >> >> > > > > > > >
> > >> >> > > > > > > > --
> > >> >> > > > > > > > Ravi
> > >> >> > > > > > > >
> > >> >> > > > > > >
> > >> >> > > > > >
> > >> >> > > > >
> > >> >> > > >
> > >> >> > >
> > >> >> >
> > >> >>
> > >> >
> > >> >
> > >>
> > >
> > >
> >
>

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