Hi Wei-Chiu, Thanx for the response. Yes, We are talking about the FBR only. Increasing the frequency limits the problem, but doesn’t seems to be solving it. With increasing cluster size, the frequency needs to be increased, and we cannot increase it indefinitely, as in some case FBR is needed. One such case is Namenode failover, In case of failover the namenode marks all the storages as Stale, it would correct them only once FBR comes, Any overreplicated blocks won’t be deleted until the storages are in stale state.
Regarding the IBR error, the block is set Completed post IBR, when the client claimed value and IBR values matches, so if there is a discrepancy here, it would alarm out there itself. If it passes over this spot, so the FBR would also be sending the same values from memory, it doesn’t check from the actual disk. DirectoryScanner would be checking if the in memory data is same as that on the disk. Other scenario where FBR could be needed is to counter a split brain scenario, but with QJM’s that is unlikely to happen. In case of any connection losses during the interval, we tend to send the BR, so should be safe here. Anyway if a client gets hold of a invalid block, it will too report to the Namenode. Other we cannot think as such, where not sending FBR can cause any issue. Let us know your thoughts on this.. -Ayush >>> On 07-Feb-2020, at 4:12 AM, Wei-Chiu Chuang <weic...@apache.org> wrote: >> Hey Ayush, >> >> Thanks a lot for your proposal. >> >> Do you mean the Full Block Report that is sent out every 6 hours per >> DataNode? >> Someone told me they reduced the frequency of FBR to 24 hours and it seems >> okay. >> >> One of the purposes of FBR was to prevent bugs in incremental block report >> implementation. In other words, it's a fail-safe mechanism. Any bugs in >> IBRs get corrected after a FBR that refreshes the state of blocks at >> NameNode. At least, that's my understanding of FBRs in its early days. >> >> On Tue, Feb 4, 2020 at 12:21 AM Ayush Saxena <ayush...@gmail.com> wrote: >> >> Hi All, >> Me and Surendra have been lately trying to minimise the impact of Block >> Reports on Namenode in huge cluster. We observed in a huge cluster, about >> 10k datanodes, the periodic block reports impact the Namenode performance >> adversely. >> We have been thinking to restrict the block reports to be triggered only >> during Namenode startup or in case of failover and eliminate the periodic >> block report. >> The main purpose of block report is to get a corrupt blocks recognised, so >> as a follow up we can maintain a service at datanode to run periodically to >> check if the block size in memory is same as that reported to namenode, and >> the datanode can alarm the namenode in case of any suspect,(We still need >> to plan this.) >> >> At the datanode side, a datanode can send a BlockReport or restore its >> actual frequency in case during the configured time period, the Datanode >> got shutdown or lost connection with the namenode, say if the datanode was >> supposed to send BR at 2100 hrs, if during the last 6 hrs there has been >> any failover or loss of connection between the namenode and datanode, it >> will trigger BR normally, else shall skip sending the BR >> >> Let us know thoughts/challenges/improvements in this. >> >> -Ayush >> >> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: hdfs-dev-unsubscr...@hadoop.apache.org >> For additional commands, e-mail: hdfs-dev-h...@hadoop.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: hdfs-dev-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-dev-h...@hadoop.apache.org
