Hi David, Thanks for the updates, looks good. Just a couple of minor comments: 1) There is a typo in "*The channel will be mutated as well when `throttle_time_ms > 0`." * Should be *muted*? 2) Since the three requests will need a new field for ` *retryQuotaViolatedException*`, we should perhaps add that change to the KIP.
Regards, Rajini On Wed, Jun 3, 2020 at 1:02 PM David Jacot <dja...@confluent.io> wrote: > Hi all, > > I have updated the KIP based on our recent discussions. I have mainly > changed the > following points: > * I have renamed the quota as suggested by Jun. > * I have changed the metrics to be "token bucket" agnostic. The idea is to > report the > burst and the rate per principal/clientid. > * I have removed the `retry.quota.violation.exception` configuration and > replaced it > with options in the respective methods' options. > > Now, the public interfaces are not tight to the algorithm that we use > internally to throttle > the requests but keep the notion of burst. I hope that this will help to > alleviate the > tokens bucket vs rate discussions. > > Please, have a look and let me know your thoughts. > > Bests, > David > > > On Wed, Jun 3, 2020 at 10:17 AM David Jacot <dja...@confluent.io> wrote: > > > Hi Rajini, > > > > Thanks for your feedback. Please find my answers below: > > > > 1) Our main goal is to protect the controller from the extreme users > > (DDoS). We want > > to protect it from large requests or repetitive requests coming from a > > single user. > > That user could be used by multiple apps as you pointed out which makes > it > > even > > worst. For instance, a buggy application could continuously create and > > delete > > topics in a tight loop. > > > > The idea of the burst is to still allow creating or deleting topics in > > batch because > > this is how applications tend to do it. However, we want to keep the > batch > > size > > under control with the burst. The burst does not allow requests of any > > size. Topics > > are accepted until the burst is passed. All the others are rejected. > > Ideally, regular > > and well behaving applications should never or rarely be throttled. > > > > 2) No, there is no explicit bound on the maximum throttle time. Having a > > maximum > > is straightforward here because the throttling time depends on the actual > > size of > > the request. > > > > 3) That's a very good question that I haven't thought of. I was thinking > > about doing > > it for the new quota only. I think that your suggestion of having a per > > method argument > > makes sense. I will update the KIP. > > > > 4) Indeed, it is outdated text. Let me update that. > > > > Regards, > > David > > > > On Wed, Jun 3, 2020 at 12:01 AM Rajini Sivaram <rajinisiva...@gmail.com> > > wrote: > > > >> Hi David, > >> > >> Thanks for the KIP. A few questions below: > >> > >> 1) The KIP says: *`Typically, applications tend to send one request to > >> create all the topics that they need`*. What would the point of > throttling > >> be in this case? If there was a user quota for the principal used by > that > >> application, wouldn't we just allow the request due to the burst value? > Is > >> the KIP specifically for the case where multiple apps with the same user > >> principal are started all at once? > >> > >> 2) Will there be a bound on the maximum throttle time? > >> > >> 3) Will *retry.quota.violation.exception* have any impact on request > quota > >> throttling or is it limited to the three requests where the new quota is > >> applied? If it is only for the new quota, perhaps it would be better to > >> add > >> an option to the relevant requests rather than use an admin client > config. > >> > >> 4) Is this outdated text, wasn't sure what this refers to : *While the > >> configuration could be set by broker, we envision to have it set only > has > >> a > >> cluster wide default for two reasons.* > >> > >> Regards, > >> > >> Rajini > >> > >> > >> On Tue, Jun 2, 2020 at 2:55 PM David Jacot <dja...@confluent.io> wrote: > >> > >> > Hi Jun, > >> > > >> > Thanks for your reply. > >> > > >> > 10. I think that both options are likely equivalent from an accuracy > >> point > >> > of > >> > view. If we put the implementation aside, conceptually, I am not > >> convinced > >> > by the used based approach because resources don't have a clear owner > >> > in AK at the moment. A topic can be created by (Principal A, no client > >> id), > >> > then can be extended by (no principal, Client B), and finally deleted > by > >> > (Principal C, Client C). This does not sound right to me and I fear > >> that it > >> > is not going to be easy to grasp for our users. > >> > > >> > Regarding the naming, I do agree that we can make it more future > proof. > >> > I propose `controller_mutations_rate`. I think that differentiating > the > >> > mutations > >> > from the reads is still a good thing for the future. > >> > > >> > 11. I am not convinced by your proposal for the following reasons: > >> > > >> > First, in my toy example, I used 101 windows and 7 * 80 requests. We > >> could > >> > effectively allocate 5 * 100 requests to the previous windows assuming > >> that > >> > they are empty. What shall we do with the remaining 60 requests? Shall > >> we > >> > allocate them to the current window or shall we divide it among all > the > >> > windows? > >> > > >> > Second, I don't think that we can safely change the behavior of all > the > >> > existing > >> > rates used because it actually changes the computation of the rate as > >> > values > >> > allocated to past windows would expire before they would today. > >> > > >> > Overall, while trying to fit in the current rate, we are going to > build > >> a > >> > slightly > >> > different version of the rate which will be even more confusing for > >> users. > >> > > >> > Instead, I think that we should embrace the notion of burst as it > could > >> > also > >> > be applied to other quotas in the future. Users don't have to know > that > >> we > >> > use the Token Bucket or a special rate inside at the end of the day. > It > >> is > >> > an > >> > implementation detail. > >> > > >> > Users would be able to define: > >> > - a rate R; and > >> > - a maximum burst B. > >> > > >> > If we change the metrics to be as follow: > >> > - the actual rate; > >> > - the burst balance in %, 0 meaning that the user is throttled; > >> > It remains disattach from the algorithm. > >> > > >> > I personally prefer this over having to define a rate and a number of > >> > windows > >> > while having to understand that the number of windows implicitly > defines > >> > the > >> > allowed burst. I think that it is clearer and easier to grasp. Don't > >> you? > >> > > >> > Best, > >> > David > >> > > >> > On Fri, May 29, 2020 at 6:38 PM Jun Rao <j...@confluent.io> wrote: > >> > > >> > > Hi, David, Anna, > >> > > > >> > > Thanks for the response. Sorry for the late reply. > >> > > > >> > > 10. Regarding exposing rate or usage as quota. Your argument is that > >> > usage > >> > > is not very accurate anyway and is harder to implement. So, let's > just > >> > be a > >> > > bit loose and expose rate. I am sort of neutral on that. (1) It > seems > >> to > >> > me > >> > > that overall usage will be relatively more accurate than rate. All > the > >> > > issues that Anna brought up seem to exist for rate too. Rate has the > >> > > additional problem that the cost of each request may not be uniform. > >> (2) > >> > In > >> > > terms of implementation, a usage based approach requires tracking > the > >> > user > >> > > info through the life cycle of an operation. However, as you > >> mentioned, > >> > > things like topic creation can generate additional > >> > > LeaderAndIsr/UpdateMetadata requests. Longer term, we probably want > to > >> > > associate those cost to the user who initiated the operation. If we > do > >> > > that, we sort of need to track the user for the full life cycle of > the > >> > > processing of an operation anyway. (3) If you prefer rate strongly, > I > >> > don't > >> > > have strong objections. However, I do feel that the new quota name > >> should > >> > > be able to cover all controller related cost longer term. This KIP > >> > > currently only covers topic creation/deletion. It would not be ideal > >> if > >> > in > >> > > the future, we have to add yet another type of quota for some other > >> > > controller related operations. The quota name in the KIP has > partition > >> > > mutation. In the future, if we allow things like topic renaming, it > >> may > >> > not > >> > > be related to partition mutation directly and it would be trickier > to > >> fit > >> > > those operations in the current quota. So, maybe sth more general > like > >> > > controller_operations_quota will be more future proof. > >> > > > >> > > 11. Regarding the difference between the token bucket algorithm and > >> our > >> > > current quota mechanism. That's a good observation. It seems that we > >> can > >> > > make a slight change to our current quota mechanism to achieve a > >> similar > >> > > thing. As you said, the issue was that we allocate all 7 * 80 > >> requests in > >> > > the last 1 sec window in our current mechanism. This is a bit > >> unintuitive > >> > > since each sec only has a quota capacity of 5. An alternative way is > >> to > >> > > allocate the 7 * 80 requests to all previous windows, each up to the > >> > > remaining quota capacity left. So, you will fill the current 1 sec > >> window > >> > > and all previous ones, each with 5. Then, it seems this will give > the > >> > same > >> > > behavior as token bucket? The reason that I keep asking this is that > >> from > >> > > an operational perspective, it's simpler if all types of quotas work > >> in > >> > the > >> > > same way. > >> > > > >> > > Jun > >> > > > >> > > On Tue, May 26, 2020 at 9:52 AM David Jacot <dja...@confluent.io> > >> wrote: > >> > > > >> > > > Hi folks, > >> > > > > >> > > > I have updated the KIP. As mentioned by Jun, I have made the > >> > > > quota per principal/clientid similarly to the other quotas. I have > >> > > > also explained how this will work in conjunction with the auto > >> > > > topics creation. > >> > > > > >> > > > Please, take a look at it. I plan to call a vote for it in the > next > >> few > >> > > > days if there are no comments in this thread. > >> > > > > >> > > > Best, > >> > > > David > >> > > > > >> > > > On Wed, May 13, 2020 at 10:57 AM Tom Bentley <tbent...@redhat.com > > > >> > > wrote: > >> > > > > >> > > > > Hi David, > >> > > > > > >> > > > > Thanks for the explanation and confirmation that evolving the > >> APIs is > >> > > not > >> > > > > off the table in the longer term. > >> > > > > > >> > > > > Kind regards, > >> > > > > > >> > > > > Tom > >> > > > > > >> > > > > >> > > > >> > > >> > > >
