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 > > > > > > > > > > > > > > > > > > > > >
