On Tue, Sep 4, 2018, at 17:47, xiongqi wu wrote: > Colin, > Thank you for comments. > see my inline reply below. > > Xiongqi (Wesley) Wu > > > On Tue, Sep 4, 2018 at 5:24 PM Colin McCabe <cmcc...@apache.org> wrote: > > > Hi Xiongqi, > > > > Thanks for this KIP. > > > > The name seems a bit ambiguous. Our compaction policies are already > > time-based, after all. It seems like this change is focused around adding > > a “max.compaction.lag.ms." Perhaps the KIP title should be something > > like "add maximum compaction lag time"? > > > > ==========> sure. I will change the title. > > > The active segment is forced to roll when either "max.compaction.lag.ms" > > > or "segment.ms" (log.roll.ms and log.roll.hours) has reached. > > > > If the max.compaction.lag.ms is low, it seems like segments will be > > rolled very frequently. This can be a source of problems in the cluster, > > since creating many different small log segments consumes a huge amount of > > cluster resources. Therefore, I would suggest adding a broker-level > > configuration which allows us to set a minimum value for > > max.compaction.lag.ms. If we let users set it on a per-topic basis, > > someone could set a value of 1 ms or something, and cause chaos. > > > > =========> this applies to segment.ms as well. Today users can set " > segment.ms" to a very low value, and cause a frequent rolling of active > segments.
Hi Xiongqi, I agree that this is an existing problem with segment.ms. However, that doesn't mean that we shouldn't fix it. As you noted, there will be more interest in these topic-level retention settings as a result of GDPR. It seems likely that pre-existing problems will cause more trouble. The fix seems relatively straightforward here -- add a broker-level minimum segment.ms that overrides per-topic minimums. We can also fail with a helpful error message when someone attempts to set an invalid configuration. > In my option, the minimum of "max.compaction.lag.ms" should be > based on the minimum of "segment.ms". Since today the minimum of segment.ms > is 1, "max.compaction.lag.ms" also starts with 1. "0" means disable. I > can use -1 as disable, but it is hard to define the meaning of 0 because we > cannot just roll the active segment immediately. That's a fair point. We should make 0 = disable, to be consistent with the other settings. best, Colin > > > -- Note that an alternative configuration is to use -1 as "disabled" and > > 0 > > > as "immediate compaction". Because compaction lag is still determined > > > based on min.compaction.lag and how long to roll an active segment, > > the > > > actual lag for compaction is undetermined if we use "0". On the other > > > hand, we can already set "min.cleanable.dirty.ratio" to achieve the > > same > > > goal. So here we choose "0" as "disabled". > > > > I would prefer -1 to be the invalid setting. Treating 0 differently than > > 1 seems strange to me. > > > > =====> see my previous comment, I am not strongly against, but 0 is not a > valid configuration in my option. So I use "0" as disabled state. > > best, > > Colin > > > > > > On Tue, Sep 4, 2018, at 15:04, xiongqi wu wrote: > > > Let's VOTE for this KIP. > > > KIP: > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-354 > > > %3A+Time-based+log+compaction+policy > > > > > > Implementation: > > > > > > https://github.com/apache/kafka/pull/5611 > > > > > > > > > > > > Xiongqi (Wesley) Wu > >
