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From Robert Newson <rnew...@apache.org>
Subject Re: [VOTE] Merge BigCouch
Date Wed, 15 May 2013 15:23:37 GMT
:)

Jan, I think you said you'd help start the IP clearance bit?

On 15 May 2013 15:03, Noah Slater <nslater@apache.org> wrote:
> PARTY TIME 🎉
>
>
> On 15 May 2013 10:40, Robert Newson <rnewson@apache.org> wrote:
>
>> Thanks everyone.
>>
>> The tally is;
>>
>> 13 +1's
>>
>> The vote passes. We'll now move on to IP clearance. Once that's done
>> the work will arrive on a feature branch in our main git repository.
>>
>> B.
>>
>>
>> On 13 May 2013 04:31, Jason Smith <jhs@iriscouch.com> wrote:
>> > Sorry, just catching up.
>> >
>> > +1
>> >
>> > On Fri, May 10, 2013 at 4:29 PM, Jan Lehnardt <jan@apache.org> wrote:
>> >> +1
>> >>
>> >> Jan
>> >> --
>> >>
>> >> On May 7, 2013, at 21:34 , Robert Newson <rnewson@apache.org> wrote:
>> >>
>> >>> Hi All,
>> >>>
>> >>> I propose to merge in the following work,
>> >>> https://github.com/rnewson/couchdb/tree/nebraska-merge-candidate to
>> >>> the official Apache CouchDB repository to a new branch (i.e, *not*
>> >>> master). Once there, the full CouchDB developer community can begin
>> >>> the work to incorporate the code here into an official release.
>> >>>
>> >>> You do not need to respond if you are in agreement. If there is no
>> >>> response in 72 hours, I will assume lazy consensus. If we reach
>> >>> consensus, I will start the IP clearance process and then the merge.
>> >>>
>> >>> As most of you know, Paul Davis and I recently sequestered ourselves
>> >>> away from society (in a place called Nebraska) to make this merge
>> >>> happen. I want to clarify that this work is not the BigCouch code you
>> >>> can see on github.com/cloudant/bigcouch but the Cloudant platform from
>> >>> which BigCouch was made. This means it is bang up to date with all the
>> >>> bug fixes and feature enhancements we've made in the last eighteen
>> >>> months or more. With that clarification made, here are our notes about
>> >>> what we achieved, what it means to the project and what isn't yet
>> >>> done;
>> >>>
>> >>> Nebraska Merge Roundup
>> >>>
>> >>>
>> >>> Stats:
>> >>>
>> >>>
>> >>> 1402 - total new commits
>> >>>
>> >>> 312 - commits written during the merge (will be reduced substantially
>> >>> by squashing)
>> >>>
>> >>> 408 - number of files changed
>> >>>
>> >>> 21,897 - number of lines added
>> >>>
>> >>> 4,277 - number of lines removed
>> >>>
>> >>> A retrospective:
>> >>>
>> >>> Bob Newson and I have come to the end of our merge sprint on getting
>> >>> BigCouch merged into Apache CouchDB. Its been a productive ten days
>> >>> here in the midwest. I managed to get Bob out to a bowling alley and
>> >>> he managed to get me to a sushi restaurant. In between the cultural
>> >>> exchanges we’ve also managed to get a significant amount of work done
>> >>> on the merging as well.
>> >>>
>> >>>
>> >>> The current status of the merge is that we’ve managed to resolve the
>> >>> differences in the single node execution of CouchDB. Both the
>> >>> JavaScript and Erlang test suites run with only one failure in the
>> >>> Erlang test suite due to a (deliberately) missing constraint on the
>> >>> number of operating system processes. This should be a relatively
>> >>> straightforward fix but was not prioritized during our limited time
to
>> >>> work on the larger issues.
>> >>>
>> >>>
>> >>> We merged a large number of performance and stability enhancements
>> >>> back into single node CouchDB as well as a number of pure bug fixes.
>> >>> The biggest highlight is a brand new compactor that is both faster and
>> >>> creates smaller and better organized post-compaction databases.
>> >>>
>> >>>
>> >>> The current status of the merge is that single node operations should
>> >>> be completely unaffected as demonstrated by the test suite passing.
On
>> >>> the other hand we haven’t yet finished getting the clustered code
>> >>> merged to use some of the new changes in single node CouchDB. The
>> >>> single most significant portion of this work involves updates to the
>> >>> internal cluster API for views to use the recently rewritten indexer
>> >>> APIs. This should be a relatively straightforward bit of work that
>> >>> we’ll be finishing over the next few weeks.
>> >>>
>> >>>
>> >>> All in all the merge work done so far has been quite successful. We’ve
>> >>> met our primary goal of getting the code merged in a fashion that does
>> >>> not affect single node operation while providing a starting point for
>> >>> the larger community to start reviewing the more significant changes
>> >>> made. Given the size of the diff between the two code bases we never
>> >>> expected to have a fully working clustered solution after ten days of
>> >>> work but we have succeeded in providing a base of work that will allow
>> >>> us and new contributors to get up to speed quickly.
>> >>>
>> >>>
>> >>> This work, coupled with work by Dave Cottlehuber and Benoît Chesneau
>> >>> on updating the build system and various other internal updates, will
>> >>> provide a solid foundation for work going forward. Its an exciting
>> >>> time for CouchDB and anyone interested should keep an eye on the next
>> >>> few releases as we ramp up work on various core aspects of the
>> >>> database.
>> >>>
>> >>>
>> >>> We’ve had an exciting few days working to prepare the road for an
>> >>> exciting next twelve to eighteen months. We hope that everyone will
>> >>> feel as excited as we do about the next twelve to eighteen months for
>> >>> Apache CouchDB. It should be an exciting ride.
>> >>>
>> >>>
>> >>>
>> >>> Things we got done
>> >>>
>> >>>
>> >>> * Large update to the source tree layout for Erlang applications. Each
>> >>> application now has a src/appname/(c_src|ebin|priv|src) structure. The
>> >>> build system has been updated.
>> >>>
>> >>> * Renamed src/couchdb to src/couch to match the Erlang convention of
>> >>> the top directory name matching the Erlang application name.
>> >>>
>> >>> * Imported Cloudant Erlang applications for clustered CouchDB. These
>> >>> are imported with their history by using git subtree and merging the
>> >>> top level commit. These are not external deps, development will happen
>> >>> within the CouchDB tree. The imported apps are:
>> >>>
>> >>>
>> >>>   * config - A couch_config replacement (Behavior is mostly identical
>> >>> to couch_config except how we listen for configuration changes
>> >>> internally to allow for smooth hot code upgrade).
>> >>>
>> >>>   * twig - An rsyslog source replacement for couch_log.
>> >>>
>> >>>   * rexi - An RPC library. Replaces Erlang’s built-in rex application
>> >>> to avoid costly safety measures in the interest of performance and
>> >>> throughput.
>> >>>
>> >>>   * mem3 - The “Dynamo” part of BigCouch responsible for managing
>> cluster state
>> >>>
>> >>>   * fabric - The internal cluster-aware CouachDB API
>> >>>
>> >>>   * ets_lru - A small library application that provides an LRU
>> >>> implementation using a couple ets tables.
>> >>>
>> >>>   * ddoc_cache - Caches design documents on each node for use in
>> >>> design handler functions. This uses an ets_lru cache with a very short
>> >>> TTL.
>> >>>
>> >>>   * chttpd - The cluster aware HTTP layer
>> >>>
>> >>>
>> >>> Each imported app also had its build system updated to use Autotools
>> >>> along with the necessary updates noted above for the new application
>> >>> layouts for existing CouchDB erlang apps.
>> >>>
>> >>>
>> >>> * Merged a large amount of updates and fixes to couch_replicator based
>> >>> on work done internally at Cloudant. Unfortunately due to an error
>> >>> when we created our internal clone we lost a bit of history in some
of
>> >>> the initial merge and have a big commit that affects
>> >>> couch_replicator_manager mostly. There are a number of other commits
>> >>> related to couch_replicator that resolve the single node vs. clustered
>> >>> differences. Some noticeable couch_replicator features:
>> >>>
>> >>>
>> >>>   * Optionally disable checkpoints so that replication can work when
>> >>> a source is read only. This should only be used for smaller databases
>> >>> as each replication call has to scan the entire source database on
>> >>> each invocation.
>> >>>
>> >>>   * A new changes_pending field in the _active_tasks output
>> >>>
>> >>>   * A fix to the continuous replication to automatically reconnect to
>> >>> a continuous changes feed when it sees a last_seq value. This allows
>> >>> for the source to selectively recycle the HTTP connections used which
>> >>> can be quite useful for “permanent” replications.
>> >>>
>> >>>   * A multitude of smaller bug fix and stability enhancements.
>> >>>
>> >>>
>> >>> Updates to single node couch:
>> >>>
>> >>>
>> >>> * We changed the by_seq tree to store a copy of the #full_doc_info{}
>> >>> record instead of the #doc_info{} record. This gives significant speed
>> >>> improvements for compaction and replication and generally anything
>> >>> that needs to walk the by_seq tree and access document bodies
>> >>> internally.
>> >>>
>> >>> * We rewrote the compactor to be significantly faster as well as
>> >>> provides significantly better compacted databases. The two main halves
>> >>> are to use a temp file and replace the use of btrees in the temp file.
>> >>> The temp file only contains a temporary copy of the document ids. At
>> >>> the end of a compaction run we then rebuild the by_id btree in the
>> >>> compaction file from this temp file. The reason this helps so much is
>> >>> that the compaction is based on the update_seq btree, which for most
>> >>> cases means that the id tree is updated in roughly random order which
>> >>> is very bad for our append only btrees. By using the tmp file we can
>> >>> stream it in order back into the compacted db file at the end of
>> >>> compacting, generating a minimum amount of garbage in the process. The
>> >>> other upgrade was to implement an external merge sort module
>> >>> (couch_emsort) that is used with this temporary file.
>> >>>
>> >>> * Reject updates to design docs that introduce updates that break
>> >>> compilation for source code. Currently we only check map and reduce
>> >>> calls as the other should provide user visible errors instead of
>> >>> inexplicably empty views.
>> >>>
>> >>> because my OCD kicked in and I was unable to resist.
>> >>>
>> >>> * Reverted a change made a long time ago that uses two file
>> >>> descriptors for each database. See the todo list.
>> >>>
>> >>> * The reason to remove the second fd is so that we can rewrite ref
>> >>> counting. Better ref counting makes everyone happy, but the real
>> >>> reason is for this next bullet point:
>> >>>
>> >>> * Optimize couch_server to not require a round trip message pass for
>> >>> opening a database that’s in the LRU. This is a significant
>> >>> performance boost for high concurrency access. We also optimized
>> >>> couch_server internals to not blow up when it’s under load.
>> >>>
>> >>> * Introduce a #leaf{} record into the revision trees. This is never
>> >>> written to disk but makes internal code a lot cleaner when dealing
>> >>> with multiple versions of rev tree values.
>> >>>
>> >>> * Some changes to couch_changes to enable clustered access. Also some
>> >>> general cleanup
>> >>>
>> >>> * Internal changes to how CouchDB is booted in Erlang land. Not very
>> >>> sexy but this removes a lot of complicated un-Erlangy bits. We still
>> >>> have a bit of work left here.
>> >>>
>> >>> * btree chunk sizes are now configurable which can allow people to
>> >>> adjust the RAM/speed tradeoffs a bit more.
>> >>>
>> >>> * We now load update validation functions on the first write. This is
>> >>> a cluster-motivated change because the clustered version of this call
>> >>> is expensive and can lead to race conditions when opening a bunch of
>> >>> db shards simultaneously. This should be invisible to external
>> >>> clients.
>> >>>
>> >>> * Disabled conflict detection for local docs. They don’t replicate
so
>> >>> there’s no point. This just led to clusters getting stuck and confused
>> >>> when there were lots of replications happening.
>> >>>
>> >>> * Changes to the multipart/mime parsing code. Necessary for clustered
>> >>> attachment uploads to split the incoming data  stream into N copies.
>> >>>
>> >>> * Don’t use init:restart/0 when reloading the ICU driver. I think
>> >>> this has a bug. But we should rewrite this driver to be a NIF anyway.
>> >>>
>> >>> * New couch OS process manager. Significantly faster access to OS
>> >>> processes under heavy load. This replaces the hard limit with a soft
>> >>> limit. Process spawned over the soft limit will be used until they’ve
>> >>> sat idle for a few minutes and then be closed. We have a todo item to
>> >>> add the hard ceiling back in (while keeping the soft ceiling).
>> >>>
>> >>> * Automatically replace some easily identifiable JS reductions with
>> >>> their builtin counterparts. Uses a regex to do the detection so its
>> >>> not too smart.
>> >>>
>> >>> * Improved view updater write batch.
>> >>>
>> >>> * Updates to couchjs’ views.js to improve index update speeds
>> >>>
>> >>> * Updates to the _stats bultin reduce to allow reduces to work over
>> >>> emitted stats objects. Sometimes clients have summary data in a doc,
>> >>> and this allows them to combine stats if they follow the same pattern
>> >>> as the builtin expects.
>> >>>
>> >>> * Added a config:reload() that is accessible by POST’ing to
>> >>> _config/_reload. Used by the JS tests to reset the config to what's
on
>> >>> disk. This should prevent those test run failures where a test fails
>> >>> leaving the config in a bad state causing all subsequent tests to
>> >>> fail. I think. Maybe.
>> >>>
>> >>> * Databases are deleted synchronously in the test suite. We may need
>> >>> to address this on Windows. But it does seem to reduce the number of
>> >>> “{error, file_exists}” failures.
>> >>>
>> >>> * I reimplemented the JS restartServer() function. There’s a new
>> >>> _restart/token URL that will given a unique value for each instance
of
>> >>> the Erlang VM. To run a restart we grab the current token value, hit
>> >>> _restart, then wait till we get a successful response with a different
>> >>> token. This appears to have made the restart strategy more robust.
>> >>>
>> >>>
>> >>>
>> >>> Things that need doing
>> >>>
>> >>>
>> >>> IP Clearance -
>> >>>
>> >>>
>> >>> We’ll need to track down if we have the CCLA as well as look at each
>> >>> source file added to make sure each one is strictly from Cloudant or
>> >>> has an amenable license. I’m pretty sure that the only one of interest
>> >>> is trunc_io.erl but we need to be thorough.
>> >>>
>> >>> documentation -
>> >>>
>> >>>
>> >>> There shouldn’t be much here since the entire point of this merge
was
>> >>> to not change the visible behavior of single node couch. A few things
>> >>> to add about the testing endpoints. Maybe an update to the compaction
>> >>> section mention the two new file names used.
>> >>>
>> >>>
>> >>> Copyright notices -
>> >>>
>> >>>
>> >>> We need to strip out copyright notices from individual files and make
>> >>> sure all files have a standard Apache License v2 header.
>> >>>
>> >>>
>> >>> clustered vhosts -
>> >>>
>> >>>
>> >>> We’ve never implemented this at Cloudant. We either need to write
a
>> >>> cluster or go back and tell people to use HAProxy (or similar) for
>> >>> such things.
>> >>>
>> >>>
>> >>> twig -
>> >>>
>> >>>
>> >>> We need to add another output type to twig that is configurable in
>> >>> some manner. Right now we spit out entire rsyslog records which isn’t
>> >>> useful for most people. We’ll need to implement the file writer from
>> >>> couch_log as well as update the _log HTTP handler to know when it can
>> >>> and can’t expect to find data on disk.
>> >>>
>> >>>
>> >>> fabric -
>> >>>
>> >>>
>> >>> This is going to need a lot of work. Specifically view access is going
>> >>> to need to be updated to work with couch_mrview and friends.
>> >>>
>> >>>
>> >>> Boot a dev cluster -
>> >>>
>> >>>
>> >>> Once we fix up the clustering code we’ll need to write instructions
>> >>> and scripts for pulling up a dev cluster.
>> >>>
>> >>>
>> >>> OTP stuff -
>> >>>
>> >>>
>> >>> We’ve updated each app but we still need to pull some parts out of
>> >>> couchdb into their own application. Specifically the HTTP layer needs
>> >>> its own app. We could probably pull out the os process/query_servers
>> >>> as well as the os daemons and friends. Once done we need to update the
>> >>> supervision trees so we don’t have things like couch starting and
>> >>> managing the replication manager process.
>> >>>
>> >>>
>> >>> ddoc_cache -
>> >>>
>> >>>
>> >>> Wire this up in couch_httpd_db to actually be used. Right now its only
>> >>> used in chttpd.
>> >>>
>> >>>
>> >>> couch_file upgrade -
>> >>>
>> >>>
>> >>> The revert to remove the second updater_fd from each #db{} record
>> >>> means that we’re back in the original position of files appearing
to
>> >>> slow down significantly under load. Since the initial hammer approach
>> >>> of just adding a second fd we’ve since discovered that the underlying
>> >>> bug is due to the way that message passing works combined with
>> >>> Erlang’s file io. Significantly though is the fact that the fix is
>> >>> rather simple to implement. A first draft of this work is on an old
>> >>> branch of mine here:
>> >>>
>> >>>
>> >>>   https://github.com/davisp/couchdb/commit/d856878
>> >>>
>> >>>
>> >>> finish the size calculating changes -
>> >>>
>> >>>
>> >>> The #leaf{} record change is to enable us to add more data size
>> >>> calculations. CouchDB master calculates a data size that account for
>> >>> all bytes that are active in a .couch file. Cloudant is interested in
>> >>> the total size of uncompressed docs and attachments minus the internal
>> >>> overhead of btrees. And there’s a fourth number to calculate based
on
>> >>> the compression level used. Having each of these numbers will be
>> >>> useful as well as the calculations they’ll enable (ie, dead bytes
in
>> >>> file, bytes used for overhead, compression ratio achieved, etc).
>> >>>
>> >>>
>> >>> couch_proc_manager -
>> >>>
>> >>>
>> >>> We need to implement the hard ceiling for capping the number of OS
>> >>> processes. We’ve started seeing a need for this at Cloudant with some
>> >>> work loads so motivation to fix this is high. The only failing etap
is
>> >>> the assertion of this ceiling.
>> >>>
>> >>>
>> >>> Synchronous db delete on Windows -
>> >>>
>> >>>
>> >>> I did this because running the test suite was driving me bonkers. I
>> >>> need to ask Dave about how this behaves on Windows (my guess is not
>> >>> well) but I think we can close things up so that it works better than
>> >>> the status quo.
>> >>
>> >
>> >
>> >
>> > --
>> > Iris Couch
>>
>
>
>
> --
> NS

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