On Wed, Jul 25, 2018 at 11:55 AM Josh Elser <[email protected]> wrote:
> ...
> My biggest take-away is that I complicated this document by tying it too
> closely with "HBase on Cloud", treating the WAL+Ratis LogService as the
> only/biggest thing to figure out. This was inaccurate and overly bold of
> me: I apologize. I think this complicated discussion on a number of
> points, and ate a good bit of some of your's time.
>
>
No need of apology.
There was healthy back and forth. You read the feedback and took it on
board.
(See below).
> My goal was to present this as an important part of a transition to the
> "cloud", giving justification to what WAL+Ratis helps HBase achieve. I
> did not want this document to be a step-by-step guide to a perfect HBase
> on Cloud design. I need to do a better job with this in the future; sorry.
That said, my feeling is that, on the whole, folks are in support of the
> proposed changes/architecture described for the WAL+Ratis work (tl;dr
> revisit WAL API, plug in current WAL implementation to any API
> modification, build new Ratis-backed WAL impl). There were some concerns
> which still need immediate action that I am aware of:
>
> * Sync with Ram and Anoop re: in-memory WAL [1]
> * Where is Ratis LogService metadata kept? How do we know what
> LogStreams were being used/maintained by a RS? How does this tie into
> recovery?
>
> There are also long-term concerns which I don't think I have an answer
> for yet (for either reasons out of my control or a lack of technical
> understanding):
>
> * Maturity of the Ratis community
> * Required performance by HBase and the ability of the LogService to
> provide that perf (Areas already mentioned: gRPC perf, fsyncs bogging
> down disks, ability to scale RAFT quorums).
> * Continue with WAL-per-RS or move to WAL-per-Region? Related to perf,
> dependent upon Ratis scalability.
> * I/O amplification on WAL retention for backup&restore and replication
> ("logstream export")
> * Ensure that LogStreams can be exported to a dist-filesystem in a
> manner which requires no additional metadata/handling (avoid more
> storage/mgmt complexity)
> * Ability to build krb5 authn into Ratis (really, gRPC)
>
> I will continue the two immediate action items. I think the latter
> concerns are some that will require fingers-on-keyboard -- I don't know
> enough about runtime characteristics without seeing it for myself.
>
> All this said, I'd like to start moving toward the point where we start
> breaking out this work into a feature-branch off of master and start
> building code. My hope is that this is amenable to everyone, with the
> acknowledge that the Ratis work is considered "experimental" and not an
> attempt to make all of HBase use Ratis-backed WALs.
>
>
Go for it.
The branch would have WAL API changes only or would it include Ratis WAL
dev? (If the latter, would that be better done over on Ratis project?).
S
> Finally, I do *not* want this message to be interpreted as me squashing
> anyone's concerns. My honest opinion is that discussion has died down,
> but I will be the first to apologize if I have missed any outstanding
> concerns. Please, please, please ping me if I am negligent.
>
> Thanks once again for everyone's participation.
>
> [1]
>
> https://docs.google.com/document/d/1Su5py_T5Ytfh9RoTTX2s20KbSJwBHVxbO7ge5ORqbCk/edit?disco=AAAACBm3RLM
>
> On 2018/07/13 20:15:45, Josh Elser <[email protected]> wrote: > Hi all,
> >
> > A long time ago, I shared a document about a (I'll call it..) "vision"
> > where we make some steps towards decoupling HBase from HDFS in an effort
> > to make deploying HBase on Cloud IaaS providers a bit easier
> > (operational simplicity, effective use of common IaaS paradigms, etc).
> >
> >
> https://docs.google.com/document/d/1Su5py_T5Ytfh9RoTTX2s20KbSJwBHVxbO7ge5ORqbCk/edit?usp=sharing
> >
> > A good ask from our Stack back then was: "[can you break down this
> > work]?" The original document was very high-level, and asking for some
> > more details make a lot of sense. Months later, I'd like to share that
> > I've updated the original document with some new content at the bottom
> > (as well as addressed some comments which went unanswered by me --
> sorry!)
> >
> > Based on a discussion I had earlier this week (and some discussions
> > during HBaseCon in California in June), I've tried to add a brief
> > "refresher" on what some of the big goals for this effort are. Please
> > check it out at your leisure and let me know what you think. Would like
> > to start getting some fingers behind this all and pump out some code :)
> >
> >
> https://docs.google.com/document/d/1Su5py_T5Ytfh9RoTTX2s20KbSJwBHVxbO7ge5ORqbCk/edit#bookmark=id.fml9ynrqagk
> >
> > - Josh
> >
>
