Glad you sorted it out! (I do want to encourage you to bump your R setting to at least 2, though. Run some tests -- I think you'll find that the difference in speed will not be noticeable, but you do get a lot more data resilience with 2.)
On Wed, Oct 7, 2015 at 6:24 PM, Vanessa Williams < vanessa.willi...@thoughtwire.ca> wrote: > Hi Dmitri, well...we solved our problem to our satisfaction but it turned > out to be something unexpected. > > The keys were two properties mentioned in a blog post on "configuring > Riak’s oft-subtle behavioral characteristics": > http://basho.com/posts/technical/riaks-config-behaviors-part-4/ > > notfound_ok= false > basic_quorum=true > > The 2nd one just makes things a little faster, but the first one is the > one whose default value of true was killing us. > > With r=1 and notfound_ok=true (default) the first node to respond, if it > didn't find the requested key, the authoritative answer was "this key is > not found". Not what we were expecting at all. > > With the changed settings, it will wait for a quorum of responses and only > if *no one* finds the key will "not found" be returned. Perfect. (Without > this setting it would wait for all responses, not ideal.) > > Now there is only one snag, which is that if the Riak node the client > connects to goes down, there will be no communication and we have a > problem. This is easily solvable with a load-balancer, though for > complicated reasons we actually don't need to do that right now. It's just > acceptable for us temporarily. Later, we'll get the load-balancer working > and even that won't be a problem. > > I *think* we're ok now. Thanks for your help! > > Regards, > Vanessa > > > > On Wed, Oct 7, 2015 at 9:33 AM, Dmitri Zagidulin <dzagidu...@basho.com> > wrote: > >> Yeah, definitely find out what the sysadmin's experience was, with the >> load balancer. It could have just been a wrong configuration or something. >> >> And yes, that's the documentation page I recommend - >> http://docs.basho.com/riak/latest/ops/advanced/configs/load-balancing-proxy/ >> Just set up HAProxy, and point your Java clients to its IP. >> >> The drawbacks to load-balancing on the java client side (yes, the cluster >> object) instead of a standalone load balancer like HAProxy, are the >> following: >> >> 1) Adding node means code changes (or at very least, config file changes) >> rolled out to all your clients. Which turns out to be a pretty serious >> hassle. Instead, HAProxy allows you to add or remove nodes without changing >> any java code or config files. >> >> 2) Performance. We've ran many tests to compare performance, and >> client-side load balancing results in significantly lower throughput than >> you'd have using haproxy (or nginx). (Specifically, you actually want to >> use the 'leastconn' load balancing algorithm with HAProxy, instead of round >> robin). >> >> 3) The health check on the client side (so that the java load balancer >> can tell when a remote node is down) is much less intelligent than a >> dedicated load balancer would provide. With something like HAProxy, you >> should be able to take down nodes with no ill effects for the client code. >> >> Now, if you load balance on the client side and you take a node down, >> it's not supposed to stop working completely. (I'm not sure why it's >> failing for you, we can investigate, but it'll be easier to just use a load >> balancer). It should throw an error or two, but then start working again >> (on the retry). >> >> Dmitri >> >> On Wed, Oct 7, 2015 at 2:45 PM, Vanessa Williams < >> vanessa.willi...@thoughtwire.ca> wrote: >> >>> Hi Dmitri, thanks for the quick reply. >>> >>> It was actually our sysadmin who tried the load balancer approach and >>> had no success, late last evening. However I haven't discussed the gory >>> details with him yet. The failure he saw was at the application level (i.e. >>> failure to read a key), but I don't know a) how he set up the LB or b) what >>> the Java exception was, if any. I'll find that out in an hour or two and >>> report back. >>> >>> I did find this article just now: >>> >>> >>> http://docs.basho.com/riak/latest/ops/advanced/configs/load-balancing-proxy/ >>> >>> So I suppose we'll give those suggestions a try this morning. >>> >>> What is the drawback to having the client connect to all 4 nodes (the >>> cluster client, I assume you mean?) My understanding from reading articles >>> I've found is that one of the nodes going away causes that client to fail >>> as well. Is that what you mean, or are there other drawbacks as well? >>> >>> If there's anything else you can recommend, or links other than the one >>> above you can point me to, it would be much appreciated. We expect both >>> node failure and deliberate node removal for upgrade, repair, replacement, >>> etc. >>> >>> Regards, >>> Vanessa >>> >>> On Wed, Oct 7, 2015 at 8:29 AM, Dmitri Zagidulin <dzagidu...@basho.com> >>> wrote: >>> >>>> Hi Vanessa, >>>> >>>> Riak is definitely meant to run behind a load balancer. (Or, at the >>>> worst case, to be load-balanced on the client side. That is, all clients >>>> connect to all 4 nodes). >>>> >>>> When you say "we did try putting all 4 Riak nodes behind a >>>> load-balancer and pointing the clients at it, but it didn't help." -- what >>>> do you mean exactly, by "it didn't help"? What happened when you tried >>>> using the load balancer? >>>> >>>> >>>> >>>> On Wed, Oct 7, 2015 at 1:57 PM, Vanessa Williams < >>>> vanessa.willi...@thoughtwire.ca> wrote: >>>> >>>>> Hi all, we are still (for a while longer) using Riak 1.4 and the >>>>> matching Java client. The client(s) connect to one node in the cluster >>>>> (since that's all it can do in this client version). The cluster itself >>>>> has >>>>> 4 nodes (sorry, we can't use 5 in this scenario). There are 2 separate >>>>> clients. >>>>> >>>>> We've tried both n_val = 3 and n_val=4. We achieve >>>>> consistency-by-writes by setting w=all. Therefore, we only require one >>>>> successful read (r=1). >>>>> >>>>> When all nodes are up, everything is fine. If one node fails, the >>>>> clients can no longer read any keys at all. There's an exception like >>>>> this: >>>>> >>>>> com.basho.riak.client.RiakRetryFailedException: >>>>> java.net.ConnectException: Connection refused >>>>> >>>>> Now, it isn't possible that Riak can't operate when one node fails, so >>>>> we're clearly missing something here. >>>>> >>>>> Note: we did try putting all 4 Riak nodes behind a load-balancer and >>>>> pointing the clients at it, but it didn't help. >>>>> >>>>> Riak is a high-availability key-value store, so... why are we failing >>>>> to achieve high-availability? Any suggestions greatly appreciated, and if >>>>> more info is required I'll do my best to provide it. >>>>> >>>>> Thanks in advance, >>>>> Vanessa >>>>> >>>>> -- >>>>> Vanessa Williams >>>>> ThoughtWire Corporation >>>>> http://www.thoughtwire.com >>>>> >>>>> >>>>> _______________________________________________ >>>>> riak-users mailing list >>>>> riak-users@lists.basho.com >>>>> http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com >>>>> >>>>> >>>> >>> >> >
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