Hi Evans, what I meant with a blog post shared would be something that goes in http://techblog.wikimedia.org/ and on https://blogs.apache.org/bigtop/, stating that we collaborated and how :)
Luca On Mon, Sep 21, 2020 at 5:44 PM Evans Ye <[email protected]> wrote: > > Yes. Overall it sounds great to me! > > I think the "summary of known pitfalls/bugs/etc.." section is worth to add > and might be a super valuable part of the whole thing. > > | "The Blog post would be a good idea, maybe something that we can share > between Wikimedia and Apache" > What do you mean by this one, specifically? Currently 3 things we can in > below. Do they match what you think or it's something else? > > 1. Bigtop wiki/blogs: > https://cwiki.apache.org/confluence/display/BIGTOP/Index > https://blogs.apache.org/bigtop/ > > 2. Success At Apache: > https://blogs.apache.org/foundation/category/SuccessAtApache > > 3. ApacheCon Talk (this year CFP is over, we can do it next year as a post > production expereince sharing) > https://apachecon.com/index.html > > - Evans > > > Luca Toscano <[email protected]> 於 2020年9月20日 週日 下午4:55寫道： >> >> Hi Evans, >> >> I am late in answering as well :) >> >> I thought about it and I think that with the right premises (example: >> this is tailored for Wikimedia's environment, it assumes that a >> cluster downtime is acceptable, etc..) the storytelling style might be >> more easy to digest than a list of steps to follow. I think that in >> all use cases different from Wikimedia there will be adjustments to >> make, and things that work/don't-work/etc.. One thing that it might be >> good to add at the end is a "summary of known pitfalls/bugs/etc.." >> found during the procedure, that in my case were the most >> time-consuming ones. I'll add it during the next few days and people >> can comment :) >> >> The Blog post would be a good idea, maybe something that we can share >> between Wikimedia and Apache? I am planning to move to BigTop during >> the upcoming quarter (October -> December), that will also show if my >> procedure works on a cluster of 60+ nodes (rather than on a small one >> of 8 nodes) :D. As soon as I have done it I'll follow up with this >> list so organize a blog post, does it sound ok? >> >> Thanks a lot for all the support! >> >> Luca >> >> On Tue, Sep 15, 2020 at 6:06 PM Evans Ye <[email protected]> wrote: >> > >> > Hey Luca, >> > >> > Sorry for the late reply. I was busy for a conference. It's just over now. >> > Anyway, I think the writing is pretty informative. But it's more like a >> > storytelling style. Also several contents are WikiMedia specific things. >> > That's why I think it's more suitable for a blogpost. >> > >> > Anyhow, I think either way it's great content. If we keep it as is, I >> > think we can make it available on Bigtop's WIKI & Blog, or even Success at >> > Apache with the title like "WikiMedia's story to migrate from CDH to >> > Bigtop". If you want to make it more like an official guide, the title >> > will be "CDH to Bigtop Migration Guide". We can state the limitation and >> > environment so that people can take it w/ a caution that it might not suit >> > their own environment. >> > >> > Which way to go depends on how much effort you'd like to take. Let me know >> > what you think so that we can move forward. >> > >> > - Evans >> > >> > Luca Toscano <[email protected]> 於 2020年9月7日 週一 下午3:39寫道： >> >> >> >> Hi Evans, >> >> >> >> thanks for the review! What are the things that you'd like to see to >> >> make them more consumable for users? I can re-shape the writing, I >> >> tried to come up with something to kick off a conversation with the >> >> community, it would be interesting to know if anybody else has a >> >> similar use case and how/if they are working on a solution. >> >> >> >> For the blogpost, maybe we can coordinate something shared between >> >> Apache and Wikimedia when the migration is done, I am sure it would be >> >> a nice example of the two Foundations collaborating :) >> >> >> >> Luca >> >> >> >> On Wed, Sep 2, 2020 at 8:21 PM Evans Ye <[email protected]> wrote: >> >> > >> >> > Hi Luca, >> >> > >> >> > I read through the doc briefly. I think the doc works very well as a >> >> > blogpost of a successful story for Wikimedia migrating from CDH to >> >> > Bigtop. However, the current writing doesn't seem to be easily >> >> > consumable for users' who are just looking into the solutions/steps for >> >> > doing similar migrations. May I know what title you would prefer if we >> >> > put the doc in Bigtop's wiki? >> >> > >> >> > What I was thinking is the cookbook for migration. But we can discuss >> >> > this. IMHO a Success at Apache[1] blogpost is also possible. But I need >> >> > to figure out who to talk to. Let me know what you think. >> >> > >> >> > [1] https://blogs.apache.org/foundation/category/SuccessAtApache >> >> > >> >> > Evans >> >> > >> >> > Evans Ye <[email protected]> 於 2020年8月30日 週日 上午3:18寫道： >> >> >> >> >> >> Hi Luca, >> >> >> >> >> >> I'm on vacation hence do not have time for review right now. I'll get >> >> >> back to you next week. >> >> >> >> >> >> The doc is definitely valuable. Once you have your production migrated >> >> >> successfully. We can prove to the other users that this is a battle >> >> >> proven solution. Even more, we can give a talk at ApacheCon or >> >> >> somewhere else to further amplify the impact of the work. This is >> >> >> definitely an open source winning case so I think it deserve a talk. >> >> >> >> >> >> Evans >> >> >> >> >> >> >> >> >> Luca Toscano <[email protected]> 於 2020年8月27日 週四 下午9:11寫道： >> >> >>> >> >> >>> Hi Evans, >> >> >>> >> >> >>> it took a while I know but I have the first version of the gdoc for >> >> >>> the upgrade: >> >> >>> >> >> >>> https://docs.google.com/document/d/1fI1mvbR1mFLV6ohU5cIEnU5hFvEE7EWnKYWOkF55jtE/edit?usp=sharing >> >> >>> >> >> >>> I tried to list all the steps involved in migrating from CDH 5 to >> >> >>> Bigtop 1.4, anybody interested should be able to comment. The idea >> >> >>> that I have is to discuss this for a few days and then possibly make >> >> >>> it permanent somewhere in the Bigtop wiki? (of course if the document >> >> >>> will be considered useful for others etc..) >> >> >>> >> >> >>> During these days I tested the procedure multiple times, and I have >> >> >>> also tested the HDFS finalize step, everything works as expected. I >> >> >>> hope to be able to move to Bigtop during the next couple of months. >> >> >>> >> >> >>> Luca >> >> >>> >> >> >>> On Tue, Jul 21, 2020 at 4:04 PM Evans Ye <[email protected]> wrote: >> >> >>> > >> >> >>> > Yes. I think a shared gdoc is prefered, and you can open up a JIRA >> >> >>> > ticket to track it. >> >> >>> > >> >> >>> > Luca Toscano <[email protected]> 於 2020年7月20日 週一 21:10 寫道： >> >> >>> >> >> >> >>> >> Hi Evans! >> >> >>> >> >> >> >>> >> What is the best medium to use for the documentation/comments ? A >> >> >>> >> shared gdoc or something similar? >> >> >>> >> >> >> >>> >> Luca >> >> >>> >> >> >> >>> >> On Thu, Jul 16, 2020 at 5:11 PM Evans Ye <[email protected]> >> >> >>> >> wrote: >> >> >>> >> > >> >> >>> >> > One thing I think would be great to have is a doc version of the >> >> >>> >> > steps for upgrade and rollback. The benefits: >> >> >>> >> > 1. Anything unexpected happened during automation, you do have >> >> >>> >> > folks can quickly understand what's going on and get into the >> >> >>> >> > investigation. >> >> >>> >> > 2. Share the doc with us to help the others OSS users for doing >> >> >>> >> > the migration. For the env specific things I think that's fine. >> >> >>> >> > We can left comment on it. At least all the other users can get >> >> >>> >> > a high level view of a proven solution. And then they can go and >> >> >>> >> > find out the rest of the pieces by themselves. >> >> >>> >> > >> >> >>> >> > For automations, I suggest to split up the automation into >> >> >>> >> > several stages, and apply some validation steps(manually is ok) >> >> >>> >> > before kicking of the next stage. >> >> >>> >> > >> >> >>> >> > Best, >> >> >>> >> > Evans >> >> >>> >> > >> >> >>> >> > >> >> >>> >> > >> >> >>> >> > >> >> >>> >> > Luca Toscano <[email protected]> 於 2020年7月15日 週三 下午9:07寫道： >> >> >>> >> >> >> >> >>> >> >> Hi everybody, >> >> >>> >> >> >> >> >>> >> >> I didn't get the time to work on this until recently, but I >> >> >>> >> >> finally >> >> >>> >> >> managed to have a reliable procedure to upgrade from CDH to >> >> >>> >> >> Bigtop 1.4 >> >> >>> >> >> and rollback if needed. The assumptions are: >> >> >>> >> >> >> >> >>> >> >> 1) It is ok to have (limited) cluster downtime. >> >> >>> >> >> 2) Rolling upgrade is not needed. >> >> >>> >> >> 3) QJM is used. >> >> >>> >> >> >> >> >>> >> >> The procedure is listed in these two scripts: >> >> >>> >> >> >> >> >>> >> >> https://github.com/wikimedia/operations-cookbooks/blob/master/cookbooks/sre/hadoop/stop-cluster.py >> >> >>> >> >> https://github.com/wikimedia/operations-cookbooks/blob/master/cookbooks/sre/hadoop/change-distro-from-cdh.py >> >> >>> >> >> >> >> >>> >> >> The code is highly dependent on my working environment, but it >> >> >>> >> >> should >> >> >>> >> >> be clear to follow when writing a tutorial about how to migrate >> >> >>> >> >> from >> >> >>> >> >> CDH to Bigtop. All the suggestions given by this mailing list >> >> >>> >> >> were >> >> >>> >> >> really useful to reach a solution! >> >> >>> >> >> >> >> >>> >> >> My next steps will be: >> >> >>> >> >> >> >> >>> >> >> 1) Keep testing Bigtop 1.4 (finalize HDFS upgrade, run more >> >> >>> >> >> hadoop >> >> >>> >> >> jobs, test Hive 2, etc..). >> >> >>> >> >> 2) Upgrade the production Hadoop cluster to Bigtop 1.4 on >> >> >>> >> >> Debian 9 >> >> >>> >> >> (HDFS 2.6.0-cdh -> 2.8.5). >> >> >>> >> >> 3) Upgrade to Bigtop 1.5 on Debian 9 (HDFS 2.8.5 -> 2.10). >> >> >>> >> >> 4) Upgrade to Debian 10. >> >> >>> >> >> >> >> >>> >> >> With automation it shouldn't be very difficult, I'll report >> >> >>> >> >> progress once made. >> >> >>> >> >> >> >> >>> >> >> Thanks a lot! >> >> >>> >> >> >> >> >>> >> >> Luca >> >> >>> >> >> >> >> >>> >> >> On Mon, Apr 13, 2020 at 9:25 AM Luca Toscano >> >> >>> >> >> <[email protected]> wrote: >> >> >>> >> >> > >> >> >>> >> >> > Hi Evans, >> >> >>> >> >> > >> >> >>> >> >> > thanks a lot for the feedback, it was exactly what I needed. >> >> >>> >> >> > The >> >> >>> >> >> > simpler the better is definitely a good advice in this use >> >> >>> >> >> > case, I'll >> >> >>> >> >> > try this week another rollout/rollback and report back :) >> >> >>> >> >> > >> >> >>> >> >> > Luca >> >> >>> >> >> > >> >> >>> >> >> > On Thu, Apr 9, 2020 at 8:09 PM Evans Ye <[email protected]> >> >> >>> >> >> > wrote: >> >> >>> >> >> > > >> >> >>> >> >> > > Hi Luca, >> >> >>> >> >> > > >> >> >>> >> >> > > Thanks for reporting back and let us know how it goes. >> >> >>> >> >> > > I don't have the exactly HDFS with QJM HA upgrade >> >> >>> >> >> > > experience. The experience I had was 0.20 non-HA upgrade to >> >> >>> >> >> > > 2.0 non-HA and then enable QJM HA, which was back in 2014. >> >> >>> >> >> > > >> >> >>> >> >> > > Regarding to rollback, I think you're right: >> >> >>> >> >> > > >> >> >>> >> >> > > it is possible to rollback to HDFS’ state before the >> >> >>> >> >> > > upgrade in case of unexpected problems. >> >> >>> >> >> > > >> >> >>> >> >> > > My previous experience is the same that the rollback is >> >> >>> >> >> > > merely a snapshot before the upgrade. If you've gone far, >> >> >>> >> >> > > then rollback cost more data lost... Our runbook is if our >> >> >>> >> >> > > sanity check failed during upgrade downtime, we perform the >> >> >>> >> >> > > rollback immediately. >> >> >>> >> >> > > >> >> >>> >> >> > > Regarding to that FSImage hole issue, I've experienced it >> >> >>> >> >> > > as well. >> >> >>> >> >> > > I managed to fix it by manually edit the FSImage with >> >> >>> >> >> > > offline image viewer[1] and delete that missing editLog in >> >> >>> >> >> > > FSImage. That actually brought my cluster back with a >> >> >>> >> >> > > little number of missing blocks. >> >> >>> >> >> > > >> >> >>> >> >> > > Our experience says that the more the steps, the more the >> >> >>> >> >> > > chance you failed the upgrade. We did good on dozen times >> >> >>> >> >> > > of testing, DEV cluster, STAGING cluster, but still got >> >> >>> >> >> > > missing blocks when upgrading Production... >> >> >>> >> >> > > >> >> >>> >> >> > > The suggestion is to get your production in good shape >> >> >>> >> >> > > first(the less decommissioned, offline DNs, disk failures, >> >> >>> >> >> > > the better). >> >> >>> >> >> > > Also, maybe you can switch to non-HA mode and do the >> >> >>> >> >> > > upgrade to simplify the things? >> >> >>> >> >> > > >> >> >>> >> >> > > Not many helps but please let us know if any progress. >> >> >>> >> >> > > Last one, have you reached out to Hadoop community? the >> >> >>> >> >> > > authors should know the most :) >> >> >>> >> >> > > >> >> >>> >> >> > > - Evans >> >> >>> >> >> > > >> >> >>> >> >> > > [1] >> >> >>> >> >> > > https://hadoop.apache.org/docs/r2.8.5/hadoop-project-dist/hadoop-hdfs/HdfsImageViewer.html >> >> >>> >> >> > > >> >> >>> >> >> > > Luca Toscano <[email protected]> 於 2020年4月8日 週三 21:03 >> >> >>> >> >> > > 寫道： >> >> >>> >> >> > >> >> >> >>> >> >> > >> Hi everybody, >> >> >>> >> >> > >> >> >> >>> >> >> > >> most of the bugs/issues/etc.. that I found while upgrading >> >> >>> >> >> > >> from CDH 5 >> >> >>> >> >> > >> to BigTop 1.4 are fixed, I am now testing (as suggested >> >> >>> >> >> > >> also in here) >> >> >>> >> >> > >> upgrade/rollback procedures for HDFS (all written in >> >> >>> >> >> > >> https://phabricator.wikimedia.org/T244499, will add >> >> >>> >> >> > >> documentation >> >> >>> >> >> > >> about this at the end I promise). >> >> >>> >> >> > >> >> >> >>> >> >> > >> I initially followed [1][2] in my Test cluster, choosing >> >> >>> >> >> > >> the Rolling >> >> >>> >> >> > >> upgrade, but when I tried to rollback (after days since >> >> >>> >> >> > >> the initial >> >> >>> >> >> > >> upgrade) I ended up in an inconsistent state and I wasn't >> >> >>> >> >> > >> able to >> >> >>> >> >> > >> recover the previous HDFS state. I didn't save the exact >> >> >>> >> >> > >> error >> >> >>> >> >> > >> messages but the situation was more or less the following: >> >> >>> >> >> > >> >> >> >>> >> >> > >> FS-Image-rollback (created at the time of the upgrade) - >> >> >>> >> >> > >> up to transaction X >> >> >>> >> >> > >> FS-Image-current - up to transaction Y, with Y = X + 10000 >> >> >>> >> >> > >> (number >> >> >>> >> >> > >> totally made up for the example) >> >> >>> >> >> > >> QJM cluster: first available transaction Z = X + 10000 + 1 >> >> >>> >> >> > >> >> >> >>> >> >> > >> When I tried to rolling rollback, the Namenode complained >> >> >>> >> >> > >> about a hole >> >> >>> >> >> > >> in the transaction log, namely at X + 1, so it refused to >> >> >>> >> >> > >> start. I >> >> >>> >> >> > >> tried to force a regular rollback, but the Namenode >> >> >>> >> >> > >> refused again >> >> >>> >> >> > >> saying that there was no available FS Image to roll back >> >> >>> >> >> > >> to. I checked >> >> >>> >> >> > >> in the Hadoop code and indeed the Namenode saves the fs >> >> >>> >> >> > >> image with >> >> >>> >> >> > >> different naming/path in case of a rolling upgrade or a >> >> >>> >> >> > >> regular >> >> >>> >> >> > >> upgrade. Both cases make sense, especially the first one >> >> >>> >> >> > >> since there >> >> >>> >> >> > >> was indeed a hole between the last transaction of the >> >> >>> >> >> > >> FS-Image-rollback and the first available transaction to >> >> >>> >> >> > >> reply on the >> >> >>> >> >> > >> QJM cluster. I chose the rolling upgrade initially since >> >> >>> >> >> > >> it was >> >> >>> >> >> > >> appealing: it promises to bring back the Namenodes to >> >> >>> >> >> > >> their previous >> >> >>> >> >> > >> versions, but keeping the data modified between upgrade >> >> >>> >> >> > >> and rollback. >> >> >>> >> >> > >> >> >> >>> >> >> > >> I then found [3], in which it is said that with QJM >> >> >>> >> >> > >> everything is more >> >> >>> >> >> > >> complicated, and a regular rollback is the only option >> >> >>> >> >> > >> available. What >> >> >>> >> >> > >> I think this mean is that due to the Edit log spread among >> >> >>> >> >> > >> multiple >> >> >>> >> >> > >> nodes, a rollback that keeps data between upgrade and >> >> >>> >> >> > >> rollback is not >> >> >>> >> >> > >> available, so worst case scenario the data modified during >> >> >>> >> >> > >> that >> >> >>> >> >> > >> timeframe is lost. Not a big deal in my case, but I want >> >> >>> >> >> > >> to triple >> >> >>> >> >> > >> check with you if this is the correct interpretation or if >> >> >>> >> >> > >> there is >> >> >>> >> >> > >> another tutorial/guide/etc.. that I haven't read with a >> >> >>> >> >> > >> different >> >> >>> >> >> > >> procedure :) >> >> >>> >> >> > >> >> >> >>> >> >> > >> Is my interpretation correct? If not, is there anybody >> >> >>> >> >> > >> with experience >> >> >>> >> >> > >> in HDFS upgrades that could shed some light on the subject? >> >> >>> >> >> > >> >> >> >>> >> >> > >> Thanks in advance! >> >> >>> >> >> > >> >> >> >>> >> >> > >> Luca >> >> >>> >> >> > >> >> >> >>> >> >> > >> >> >> >>> >> >> > >> >> >> >>> >> >> > >> [1] >> >> >>> >> >> > >> https://hadoop.apache.org/docs/r2.8.5/hadoop-project-dist/hadoop-hdfs/HdfsUserGuide.html#Upgrade_and_Rollback >> >> >>> >> >> > >> [2] >> >> >>> >> >> > >> https://hadoop.apache.org/docs/r2.8.5/hadoop-project-dist/hadoop-hdfs/HdfsRollingUpgrade.html >> >> >>> >> >> > >> [3] >> >> >>> >> >> > >> https://hadoop.apache.org/docs/r2.8.5/hadoop-project-dist/hadoop-hdfs/HDFSHighAvailabilityWithQJM.html#HDFS_UpgradeFinalizationRollback_with_HA_Enabled
