Many File Open Issue : Spring Boot 2.3.0 -> Spring Boot 2.3.1

[harutobi]

I recently upgraded 2.3.0.RELEASE to 2.3.1.RELEASE. (1 days ago)
However, an oddity was discovered in which FileOpen occupancy rapidly increased
I checked through 'lsof' command in the linux terminal, but a lot of 'socket' was found.

(1 process file open count limit over : 65535..)
java      10307 account *505u     sock                0,7       0t0 148421069 protocol: TCP
java      10307 account *506u     sock                0,7       0t0 148416289 protocol: TCP
java      10307 account *507u     sock                0,7       0t0 148416293 protocol: TCP
java      10307 account *508u     sock                0,7       0t0 148421073 protocol: TCP
java      10307 account *509u     sock                0,7       0t0 148421070 protocol: TCP
java      10307 account *510u     sock                0,7       0t0 148421075 protocol: TCP
java      10307 account *511u     sock                0,7       0t0 148416300 protocol: TCP
java      10307 account *512u     sock                0,7       0t0 148416298 protocol: TCP
java      10307 account *513u     sock                0,7       0t0 148416313 protocol: TCP
java      10307 account *514u     sock                0,7       0t0 148421098 protocol: TCP

ErrorCallbackNotImplemented: io.netty.channel.ChannelException: io.netty.channel.unix.Errors$NativeIoException: newSocketStream(..) failed: Too many open files
ChannelException: io.netty.channel.unix.Errors$NativeIoException: newSocketStream(..) failed: Too many open files
    at io.netty.channel.unix.Socket.newSocketStream0(Socket.java:421)
    at io.netty.channel.epoll.LinuxSocket.newSocketStream(LinuxSocket.java:319)
    at io.netty.channel.epoll.LinuxSocket.newSocketStream(LinuxSocket.java:323)
    at io.netty.channel.epoll.EpollSocketChannel.<init>(EpollSocketChannel.java:45)
    at reactor.netty.resources.DefaultLoopEpoll.getChannel(DefaultLoopEpoll.java:45)
...
(36 additional frame(s) were not displayed)

NativeIoException: newSocketStream(..) failed: Too many open files

<Before: SpringBoot 2.3.0>

• FileOpen Size : 100 (average)

<After: SpringBoot 2.3.1>

• FileOpen Size Over Flow : 65535 (ulimit open size)

There is no problem until 2.3.0. If you upgrade the version to 2.3.1, a problem occurs.
after downgrade version to 2.3.0, file open problem solved.

[bclozel]

This looks a lot like #21923

Could you try and downgrade the Netty tcnative dependency as suggested in the other issue and report back here with your findings?

Thanks!

[bclozel]

This seems to be caused by reactor/reactor-netty#1152

Could you try overriding the reactor-netty dependency to the latest 0.9.9.BUILD-SNAPSHOT and this if this fixes the issue?

Thanks!

[snicoll]

You can override reactor-bom.version to Dysprosium-BUILD-SNAPSHOT. We've also switched Spring Boot 2.3.2.BUILD-SNAPSHOT to use this version by default so in half an hour you could just switch your build to 2.3.2.BUILD-SNAPSHOT.

[harutobi]

@bclozel @snicoll
Thank you for answer.
I solved from dependency override that io.projectreactor.netty
0.9.7.RELEASE and 0.9.9.BUILD-SNAPSHOT.

[bclozel]

Downgrading is not fixing the problem, but rather a temporary workaround.

Unless you expect being stuck on that particular reactor netty version forever, testing the version shipping the snapshot would really help the team confirm that this problem is fixed.

Thanks

[bclozel]

Since 0.9.9 fixed the issue, I'm closing this as a duplicate of #21923