Actually returning an empty fetch request may still be useful to reduce the throttle time due to request quota violation because the FetchResponse send time will be less. I just updated the KIP.
Rajini, does that address your concern? On Tue, Jan 16, 2018 at 7:01 PM, Becket Qin <becket....@gmail.com> wrote: > Thanks for the reply, Jun. > > Currently the byte rate quota does not apply to HeartbeatRequest, > JoinGroupRequest/SyncGroupRequest. So the only case those requests are > throttled is because the request quota is violated. In that case, the > throttle time does not really matter whether we return a full FetchResponse > or an empty one. Would it be more consistent if we throttle based on the > actual throttle time / channel mute time? > > Thanks, > > Jiangjie (Becket) Qin > > On Tue, Jan 16, 2018 at 3:45 PM, Jun Rao <j...@confluent.io> wrote: > >> Hi, Jiangjie, >> >> You are right that the heartbeat is done in a channel different from the >> fetch request. I think it's still useful to return an empty fetch response >> when the quota is violated. This way, the throttle time for the heartbeat >> request won't be large. I agree that we can just mute the channel for the >> fetch request for the throttle time computed based on a full fetch >> response. This probably also partially addresses Rajini's #1 concern. >> >> Thanks, >> >> Jun >> >> On Mon, Jan 15, 2018 at 9:27 PM, Becket Qin <becket....@gmail.com> wrote: >> >> > Hi Rajini, >> > >> > Thanks for the comments. Pleas see the reply inline. >> > >> > Hi Jun, >> > >> > Thinking about the consumer rebalance case a bit more, I am not sure if >> we >> > need to worry about the delayed rebalance due to quota violation or not. >> > The rebalance actually uses a separate channel to coordinator. Therefore >> > unless the request quota is hit, the rebalance won't be throttled. Even >> if >> > request quota is hit, it seems unlikely to be delayed long. So it looks >> > that we don't need to unmute the channel earlier than needed. Does this >> > address your concern? >> > >> > Thanks, >> > >> > Jiangjie (Becket) Qin >> > >> > On Mon, Jan 15, 2018 at 4:22 AM, Rajini Sivaram < >> rajinisiva...@gmail.com> >> > wrote: >> > >> > > Hi Becket, >> > > >> > > A few questions: >> > > >> > > 1. KIP says: *Although older client implementations (prior to >> knowledge >> > of >> > > this KIP) will immediately send the next request after the broker >> > responds >> > > without paying attention to the throttle time field, the broker is >> > > protected by virtue of muting the channel for time X. i.e., the next >> > > request will not be processed until the channel is unmuted. * >> > > For fetch requests, the response is sent immediately and the mute >> time on >> > > the broker based on empty fetch response will often be zero (unlike >> the >> > > throttle time returned to the client based on non-empty response). >> Won't >> > > that lead to a tight loop of fetch requests from old clients >> > (particularly >> > > expensive with SSL)? Wouldn't it be better to retain current behaviour >> > for >> > > old clients? Also, if we change the behaviour for old clients, client >> > > metrics that track throttle time will report a lot of throttle >> unrelated >> > to >> > > actual throttle time. >> > > >> > For consumers, if quota is violated, the throttle time on the broker >> will >> > not be 0. It is just that the throttle time will not be increasing >> because >> > the consumer will return an empty response in this case. So there should >> > not be a tight loop. >> > >> > >> > > 2. KIP says: *The usual idle timeout i.e., connections.max.idle.ms >> > > <http://connections.max.idle.ms> will still be honored during the >> > throttle >> > > time X. This makes sure that the brokers will detect client connection >> > > closure in a bounded time.* >> > > Wouldn't it be better to bound maximum throttle time to >> > > *connections.max.idle.ms >> > > <http://connections.max.idle.ms>*? If we mute for a time greater than >> > > *connections.max.idle.ms >> > > <http://connections.max.idle.ms>* and then close a client connection >> > > simply >> > > because we had muted it on the broker for a longer throttle time, we >> > force >> > > a reconnection and read the next request from the new connection >> straight >> > > away. This feels the same as a bound on the quota of * >> > > connections.max.idle.ms >> > > <http://connections.max.idle.ms>*, but with added load on the broker >> for >> > > authenticating another connection (expensive with SSL). >> > > >> > I think we need to think about the consumer prior to and after this KIP >> > separately. >> > >> > For consumer prior to this KIP, even if we unmute the channel after >> > connection.max.idle.ms, it is likely that the consumers have already >> > reached request.timeout.ms before that and has reconnected to the >> broker. >> > So there is no real difference whether we close the throttled channel or >> > not. >> > >> > For consumers after the KIP, because they will honor the throttle time, >> > they will back off until throttle time is reached. If that throttle >> time is >> > longer than connection.max.idle.ms, it seems not a big overhead because >> > there will only be one connection re-establishment in quite a few >> minutes. >> > Compared with such overhead, it seems more important to honor the quota >> so >> > the broker can survive. >> > >> > >> > > 3. Are we changing the behaviour of network bandwidth quota for >> > > Produce/Fetch and retaining current behaviour for request quotas? >> > > >> > This is going to be applied to all the quota. Including request quotas. >> > >> > >> > > >> > > Thanks, >> > > >> > > Rajini >> > > >> > > >> > > >> > > On Wed, Jan 10, 2018 at 10:29 PM, Jun Rao <j...@confluent.io> wrote: >> > > >> > > > Hi, Jiangjie, >> > > > >> > > > Thanks for the updated KIP. +1 >> > > > >> > > > Jun >> > > > >> > > > On Mon, Jan 8, 2018 at 7:45 PM, Becket Qin <becket....@gmail.com> >> > wrote: >> > > > >> > > > > Thanks for the comments, Jun. >> > > > > >> > > > > 1. Good point. >> > > > > 2. Also makes sense. Usually the connection.max.idle.ms is high >> > enough >> > > > so >> > > > > the throttling is impacted. >> > > > > >> > > > > I have updated the KIP to reflect the changes. >> > > > > >> > > > > Thanks, >> > > > > >> > > > > Jiangjie (Becket) Qin >> > > > > >> > > > > >> > > > > On Mon, Jan 8, 2018 at 6:30 PM, Jun Rao <j...@confluent.io> wrote: >> > > > > >> > > > > > Hi, Jiangjie, >> > > > > > >> > > > > > Sorry for the late response. The proposal sounds good overall. A >> > > couple >> > > > > of >> > > > > > minor comments below. >> > > > > > >> > > > > > 1. For throttling a fetch request, we could potentially just >> send >> > an >> > > > > empty >> > > > > > response. We can return a throttle time calculated from a full >> > > > response, >> > > > > > but only mute the channel on the server based on a throttle time >> > > > > calculated >> > > > > > based on the empty response. This has the benefit that the >> server >> > > will >> > > > > mute >> > > > > > the channel much shorter, which will prevent the consumer from >> > > > > rebalancing >> > > > > > when throttled. >> > > > > > >> > > > > > 2. The wiki says "connections.max.idle.ms should be ignored >> during >> > > the >> > > > > > throttle time X." This has the potential issue that a server may >> > not >> > > > > detect >> > > > > > that a client connection is already gone until after an >> arbitrary >> > > > amount >> > > > > of >> > > > > > time. Perhaps we could still just close a connection if the >> server >> > > has >> > > > > > muted it for longer than connections.max.idle.ms. This will at >> > least >> > > > > bound >> > > > > > the time for a server to detect closed client connections. >> > > > > > >> > > > > > Thanks, >> > > > > > >> > > > > > Jun >> > > > > > >> > > > > > >> > > > > > On Mon, Nov 20, 2017 at 5:30 PM, Becket Qin < >> becket....@gmail.com> >> > > > > wrote: >> > > > > > >> > > > > > > Hi, >> > > > > > > >> > > > > > > We would like to start the voting thread for KIP-219. The KIP >> > > > proposes >> > > > > to >> > > > > > > improve the quota communication between the brokers and >> clients, >> > > > > > especially >> > > > > > > for cases of long throttling time. >> > > > > > > >> > > > > > > The KIP wiki is following: >> > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP- >> > > > > > 219+-+Improve+quota+ >> > > > > > > communication >> > > > > > > >> > > > > > > The discussion thread is here: >> > > > > > > http://markmail.org/search/?q=kafka+KIP-219#query:kafka% >> > > > > > > 20KIP-219+page:1+mid:ooxabguy7nz7l7zy+state:results >> > > > > > > >> > > > > > > Thanks, >> > > > > > > >> > > > > > > Jiangjie (Becket) Qin >> > > > > > > >> > > > > > >> > > > > >> > > > >> > > >> > >> > >
