On 06/02/2017 05:07 AM, Eyal Lebedinsky wrote: > On 02/06/17 21:48, Roger Heflin wrote: >> If the machine mounting the file and doing the tail has read from the >> file and there is new data added in that last block and because of the >> rate the data is coming into the file the timestamp on the file does >> not change then the client nfs host will not know that the last block >> has changed and will not know to reread it (it is already in cache). >> If it is this bug/feature nfs has worked this way I think pretty much >> forever at a larger scale (2 hosts each writing every other block, if >> the timestamp does not change then each node will see the others >> blocks as empty because of cache, at least until the timestamp changes >> from what it knows it wrote). The trick my previous job implemented >> was to make sure the timestamp on the file moved ahead at least one >> second so that the clients knew the file changed. but if tail is >> actively reading it while things are getting written into it I don't >> see a way it would be able to work that well. >> >> What you are describing sounds like a variant of this issue. > > Thanks Roger, > > Interesting, though I wonder why it worked very well until the latest > kernel > series (3.10/3.11) which started showing the problem. Looks like a new > "feature" > to me. > > BTW, the server is also the time server and the two are well > synchronised. When > a zero block shows up it can take a minute or two before the real data > shows up. > I use 'less' to view the file, hit refresh (Shift-G) and soon a line of > zeroes > comes along. I kept refreshing for a few minutes until the good data shows. > > When I originally notices the problem (a monitoring script started > showing garbage), > the monitored file was updated once a minute and it needed to be updated > two or > three times before the real data was exported. > > which I consider rather a long time for a file to present wrong content > (over nfs). > > Maybe there is an export (or mount) option I can use? > > Also, I could not find a reference to this problem when I investigated > the issue > initially, and as such I assumed it is my setup. But the server (f19) > had no > updates or changes for a long while. It is clearly the new kernels > exposing this, > and I tested more that one client machine to verify that they also show > the issue. Newer kernels use NFSv4 by default. I can't remember what F19 uses natively or if it has issues with NFSv4 clients (it may not really implement NFSv4 properly or improperly negotiates protocol changes). You might try forcing NFSv3 mounts and see if that clears the problem. You may want to look at the "noac" option on the clients as well as the "acregmin", "acregmax", "acdirmin", "acdirmax" and "actimeo" values (see "man 5 nfs"). Defaults and such have changed with different kernels and perhaps there's some incompatibility. ---------------------------------------------------------------------- - Rick Stevens, Systems Engineer, AllDigital ricks@xxxxxxxxxxxxxx - - AIM/Skype: therps2 ICQ: 226437340 Yahoo: origrps2 - - - - Cuteness can be overcome through sufficient bastardry - - --Mark 'Kamikaze' Hughes - ---------------------------------------------------------------------- _______________________________________________ users mailing list -- users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to users-leave@xxxxxxxxxxxxxxxxxxxxxxx
