Thx Joseph. Writing back the entire blob is costly instead of writing back only the 2 bytes. In this case this record is just a chunk of large snapshot that is getting written. So it multiplies.
Should I open a jira to track and resolve this or something like this is already open? Thx > On Jun 5, 2018, at 9:10 AM, Joseph Wu <jos...@mesosphere.io> wrote: > > The two-byte difference is most likely coming from the "learned" field: > https://github.com/apache/mesos/blob/master/src/messages/log.proto#L49 > > The first time an entry is recorded, the entry is "unlearned", basically > meaning that the entry has not been written to a quorum of masters (yet). > Once a quorum of masters indicate to each other that they have written an > entry, they then flip the bit to "learned". > > This process is mandatory for Paxos to work, but I can see how overwriting an > entry could be expensive. There's no particular restriction on why we must > overwrite the entire entry, except that we currently use the position number > (i.e. 6506690 in your example) as the key in the leveldb implementation. > >> On Tue, Jun 5, 2018 at 12:30 AM, meghdoot bhattacharya >> <meghdoo...@yahoo.com.invalid> wrote: >> Recently investigation of logs of aurora around snapshot creations in >> replicated log come up with this >> I0601 21:57:27.322444 144 log.cpp:577] Attempting to append 524304 bytes >> to the logI0601 21:57:27.322501 144 coordinator.cpp:348] Coordinator >> attempting to write APPEND action at position 6506690I0601 21:57:27.323122 >> 139 replica.cpp:539] Replica received write request for position 6506690 >> from __req_res__(3685)@x.x.x.x:yyyyI0601 21:57:27.443131 139 >> leveldb.cpp:341] Persisting action (524331 bytes) to leveldb took >> 119.847993msI0601 21:57:27.443208 139 replica.cpp:710] Persisted action >> APPEND at position 6506690I0601 21:57:27.443437 139 replica.cpp:693] >> Replica received learned notice for position 6506690 from @0.0.0.0:0I0601 >> 21:57:27.478754 139 leveldb.cpp:341] Persisting action (524333 bytes) to >> leveldb took 35.278735msI0601 21:57:27.478818 139 replica.cpp:710] >> Persisted action APPEND at position 6506690 >> >> >> It seems there are dual writes to leveldb for the same record (with 2 byte >> diff). Becomes expensive if that is the case for large records. Hoping to >> get some insights. >> Thx >
