Thanks for the detailed write up Jiangjie. Overall the proposal looks good to me. I have a few implementation detail questions that don't necessarily need to block progress:
When searching by timestamp, broker will start from the earliest log > segment and check the last time index entry. If the timestamp of the last > time index entry is greater than the target timestamp, the broker will do > binary search on that time index to find the closest index entry and scan > the log from there. Otherwise it will move on to the next log segment. > Does this mean having more old data will increase the length of timestamp searches? Have you considered searching from the most recent segment? I am thinking looking up more recent data is likely the common case but haven't thought about it too much. To enforce time based log retention, the broker will check the last time > index entry of a log segment. The timestamp will be the latest timestamp of > the messages in the log segment. So if that timestamp expires, the broker > will delete the log segment. > Does this mean the choice between message.timestamp.type affects retention time? When broker receives a message, if the message is not rejected due to > timestamp exceeds threshold, the message will be appended to the log. (The > timestamp will either be LogAppendTime or CreateTime depending on the > configuration) > What happens when message.timestamp.type is changed? Are there any special considerations for compacted topics? Thank you, Grant On Mon, Apr 18, 2016 at 8:50 AM, Ismael Juma <ism...@juma.me.uk> wrote: > Hi Jiangjie, > > Thanks for the KIP, it's a nice improvement. Since it seems like we have > been using the voting thread for discussion, I'll do the same. > > A few minor comments/questions: > > 1. The proposed name for the time index file `SegmentBaseOffset.timeindex`. > Would `SegmentBaseOffset.time-index` be a little better? It would clearly > separate the type of index in case we add additional index types in the > future. > 2. When describing the time index entry, we say "Offset - the next offset > when the time index entry is inserted". I found the mention of `next` a bit > confusing as it looks to me like the time index entry has the first offset > in the message set. > 3. We say "The default initial / max size of the time index files is the > same as the offset index files. (time index entry is 1.5x of the size of > offset index entry, user should set the configuration accordingly)". It may > be worth elaborating a little on what a user should do with regards to this > configuration when upgrading (ie maybe under "Compatibility, Deprecation, > and Migration Plan"). > 4. In a previous vote thread, Jun said "The simplest thing is probably > to change > the default index size to 2MB to match the default log segment size" and > you seemed to agree. I couldn't find anything about this in the KIP. Are we > still doing it? > 5. We say "Instead, it is only monotonically increasing within each time > index file. i.e. It is possible that the time index file for a later log > segment contains smaller timestamp than some timestamp in the time index > file of an earlier segment.". I think it would be good to explain under > which scenario a time index file for a later log segment contains a smaller > timestamp (is this only when CreateTime is used?). > 6. We say "When searching by timestamp, broker will start from the earliest > log segment and check the last time index entry.". The existing logic > searches from newest segment backwards. Is there a reason why we are > changing it? > 7. Do you mind if I fix typos and minor grammar issues directly in the > wiki? It seems easier than doing that via email. > > Thanks, > Ismael > > On Thu, Apr 7, 2016 at 1:44 AM, Becket Qin <becket....@gmail.com> wrote: > > > Hi all, > > > > I updated KIP-33 based on the initial implementation. Per discussion on > > yesterday's KIP hangout, I would like to initiate the new vote thread for > > KIP-33. > > > > The KIP wiki: > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-33+-+Add+a+time+based+log+index > > > > Here is a brief summary of the KIP: > > 1. We propose to add a time index for each log segment. > > 2. The time indices are going to be used of log retention, log rolling > and > > message search by timestamp. > > > > There was an old voting thread which has some discussions on this KIP. > The > > mail thread link is following: > > > > > http://mail-archives.apache.org/mod_mbox/kafka-dev/201602.mbox/%3ccabtagwgoebukyapfpchmycjk2tepq3ngtuwnhtr2tjvsnc8...@mail.gmail.com%3E > > > > I have the following WIP patch for reference. It needs a few more unit > > tests and documentation. Other than that it should run fine. > > > > > https://github.com/becketqin/kafka/commit/712357a3fbf1423e05f9eed7d2fed5b6fe6c37b7 > > > > Thanks, > > > > Jiangjie (Becket) Qin > > > -- Grant Henke Software Engineer | Cloudera gr...@cloudera.com | twitter.com/gchenke | linkedin.com/in/granthenke
