This should work for locally attached storage for sure. On Wed, Apr 15, 2020 at 3:52 PM Vladimir Rodionov <vladrodio...@gmail.com> wrote:
> FileOutputStream.getFileChannel().force(true) will get all durability we > need. Just a simple code change? > > > On Wed, Apr 15, 2020 at 12:32 PM Andrew Purtell <andrew.purt...@gmail.com> > wrote: > >> This thread talks of “durability” via filesystem characteristics but also >> for single system quick Start type deployments. For durability we need >> multi server deployments. No amount of hacking a single system deployment >> is going to give us durability as users will expect (“don’t lose my data”). >> I believe my comments are on topic. >> >> >> > On Apr 15, 2020, at 11:03 AM, Nick Dimiduk <ndimi...@apache.org> wrote: >> > >> > On Wed, Apr 15, 2020 at 10:28 AM Andrew Purtell <apurt...@apache.org> >> wrote: >> > >> >> Nick's mail doesn't make a distinction between avoiding data loss via >> >> typical tmp cleaner configurations, unfortunately adjacent to mention >> of >> >> "durability", and real data durability, which implies more than what a >> >> single system configuration can offer, no matter how many tweaks we >> make to >> >> LocalFileSystem. Maybe I'm being pedantic but this is something to be >> >> really clear about IMHO. >> >> >> > >> > I prefer to focus the attention of this thread to the question of data >> > durability via `FileSystem` characteristics. I agree that there are >> > concerns of durability (and others) around the use of the path under >> /tmp. >> > Let's keep that discussion in the other thread. >> > >> >> On Wed, Apr 15, 2020 at 10:05 AM Sean Busbey <bus...@apache.org> >> wrote: >> >> >> >>> I think the first assumption no longer holds. Especially with the move >> >>> to flexible compute environments I regularly get asked by folks what >> >>> the smallest HBase they can start with for production. I can keep >> >>> saying 3/5/7 nodes or whatever but I guarantee there are folks who >> >>> want to and will run HBase with a single node. Probably those >> >>> deployments won't want to have the distributed flag set. None of them >> >>> really have a good option for where the WALs go, and failing loud when >> >>> they try to go to LocalFileSystem is the best option I've seen so far >> >>> to make sure folks realize they are getting into muddy waters. >> >>> >> >>> I agree with the second assumption. Our quickstart in general is too >> >>> complicated. Maybe if we include big warnings in the guide itself, we >> >>> could make a quickstart specific artifact to download that has the >> >>> unsafe disabling config in place? >> >>> >> >>> Last fall I toyed with the idea of adding an "hbase-local" module to >> >>> the hbase-filesystem repo that could start us out with some >> >>> optimizations for single node set ups. We could start with a fork of >> >>> RawLocalFileSystem (which will call OutputStream flush operations in >> >>> response to hflush/hsync) that properly advertises its >> >>> StreamCapabilities to say that it supports the operations we need. >> >>> Alternatively we could make our own implementation of FileSystem that >> >>> uses NIO stuff. Either of these approaches would solve both problems. >> >>> >> >>> On Wed, Apr 15, 2020 at 11:40 AM Nick Dimiduk <ndimi...@apache.org> >> >> wrote: >> >>>> >> >>>> Hi folks, >> >>>> >> >>>> I'd like to bring up the topic of the experience of new users as it >> >>>> pertains to use of the `LocalFileSystem` and its associated (lack of) >> >>> data >> >>>> durability guarantees. By default, an unconfigured HBase runs with >> its >> >>> root >> >>>> directory on a `file:///` path. This patch is picked up as an >> instance >> >> of >> >>>> `LocalFileSystem`. Hadoop has long offered this class, but it has >> never >> >>>> supported `hsync` or `hflush` stream characteristics. Thus, when >> HBase >> >>> runs >> >>>> on this configuration, it is unable to ensure that WAL writes are >> >>> durable, >> >>>> and thus will ACK a write without this assurance. This is the case, >> >> even >> >>>> when running in a fully durable WAL mode. >> >>>> >> >>>> This impacts a new user, someone kicking the tires on HBase following >> >> our >> >>>> Getting Started docs. On Hadoop 2.8 and before, an unconfigured HBase >> >>> will >> >>>> WARN and cary on. Hadoop 2.10+, HBase will refuse to start. The book >> >>>> describes a process of disabling enforcement of stream capability >> >>>> enforcement as a first step. This is a mandatory configuration for >> >>> running >> >>>> HBase directly out of our binary distribution. >> >>>> >> >>>> HBASE-24086 restores the behavior on Hadoop 2.10+ to that of running >> on >> >>>> 2.8: log a warning and cary on. The critique of this approach is that >> >>> it's >> >>>> far too subtle, too quiet for a system operating in a state known to >> >> not >> >>>> provide data durability. >> >>>> >> >>>> I have two assumptions/concerns around the state of things, which >> >>> prompted >> >>>> my solution on HBASE-24086 and the associated doc update on >> >> HBASE-24106. >> >>>> >> >>>> 1. No one should be running a production system on `LocalFileSystem`. >> >>>> >> >>>> The initial implementation checked both for `LocalFileSystem` and >> >>>> `hbase.cluster.distributed`. When running on the former and the >> latter >> >> is >> >>>> false, we assume the user is running a non-production deployment and >> >>> carry >> >>>> on with the warning. When the latter is true, we assume the user >> >>> intended a >> >>>> production deployment and the process terminates due to stream >> >> capability >> >>>> enforcement. Subsequent code review resulted in skipping the >> >>>> `hbase.cluster.distributed` check and simply warning, as was done on >> >> 2.8 >> >>>> and earlier. >> >>>> >> >>>> (As I understand it, we've long used the `hbase.cluster.distributed` >> >>>> configuration to decide if the user intends this runtime to be a >> >>> production >> >>>> deployment or not.) >> >>>> >> >>>> Is this a faulty assumption? Is there a use-case we support where we >> >>>> condone running production deployment on the non-durable >> >>> `LocalFileSystem`? >> >>>> >> >>>> 2. The Quick Start experience should require no configuration at all. >> >>>> >> >>>> Our stack is difficult enough to run in a fully durable production >> >>>> environment. We should make it a priority to ensure it's as easy as >> >>>> possible to try out HBase. Forcing a user to make decisions about >> data >> >>>> durability before they even launch the web ui is a terrible >> experience, >> >>> in >> >>>> my opinion, and should be a non-starter for us as a project. >> >>>> >> >>>> (In my opinion, the need to configure either `hbase.rootdir` or >> >>>> `hbase.tmp.dir` away from `/tmp` is equally bad for a Getting Started >> >>>> experience. It is a second, more subtle question of data durability >> >> that >> >>> we >> >>>> should avoid out of the box. But I'm happy to leave that for another >> >>>> thread.) >> >>>> >> >>>> Thank you for your time, >> >>>> Nick >> >>> >> >> >> >> >> >> -- >> >> Best regards, >> >> Andrew >> >> >> >> Words like orphans lost among the crosstalk, meaning torn from truth's >> >> decrepit hands >> >> - A23, Crosstalk >> >> >> >
