+1 On 08 May 2013, at 7:04 PM, Joan Touzet <woh...@apache.org> wrote:
> +1 > > On Tue, May 07, 2013 at 04:02:09PM -0500, Paul Davis wrote: >> +1 >> >> On Tue, May 7, 2013 at 3:52 PM, Russell Branca <chewbra...@gmail.com> wrote: >>> +1 >>> >>> >>> Very excited to see this! Great work! >>> >>> >>> -Russell >>> >>> >>> On Tue, May 7, 2013 at 1:44 PM, Robert Newson <rnew...@apache.org> wrote: >>> >>>> FYI: A zip of this work is available at >>>> http://people.apache.org/~rnewson/dist/nebraska-merge-candidate.zip >>>> made by 'git archive -o nebraska-merge-candidate.zip >>>> nebraska-merge-candidate' >>>> >>>> On 7 May 2013 21:34, Robert Newson <rnew...@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. >>>> > > -- > Joan Touzet | jo...@atypical.net | wohali everywhere else
