Temurin-build: Move xLinux build machines to CentOS7

[sxa]

RHEL6/CentOS6 is not being supported beyond November 2020 (Source: https://wiki.centos.org/About/Product)

We currently build all our x64 JDKs on CentOS6

We need to look at whether we can reasonably swit4ch the building of this to e on CentOS7 or whether we need isolated (unpatched) systems to continue building the 8 and 11 streams that we have built on the old releases in order to avoid introducing incompatibilities.

On other Linux platforms, we already build on CentOS/RHEL7.

This will increase the GLIBC level on xlinux from 2.12 to 2.17 - we currently have this message on our supported platforms page:

Note: Any other Linux distributions that have a minimum glibc
version 2.12 on x86 or version glibc version 2.17 on other
architectures are expected to function without problems.

[sxa]

FYI @AdoptOpenJDK/tsc:

SLES12 uses glibc 2.22
Ubuntu 14.04 is glibc 2.19
Debian 8 (jessie) is glibc 2.19

It seems highliy unlikely that anyone is using something earlier than those in production now (Debian 7/wheezy has 2.13, SLES11 2.11), but a move to 2.17 would break anything earlier than the versions above.

[pshipton]

@DanHeidinga fyi

[DanHeidinga]

I'm slightly concerned about this due to the changed glibc level. Starting some discussions internally to determine how much of an issue this will (or won't) be for us

[DanHeidinga]

@sxa What's the timeline for making this change? Trying to determine how long my stakeholders have to get back to me with concerns

[sxa]

I'm not proposing to do it immediately (though may be nice to switch JDK15 ...) so plenty of time for you to contact others. If that changes I will of course let you know

[pshipton]

Agreed that JDK15+ should at least change, even if jdk8-11 don't or use different techniques to keep compatibility with glibc 2.12.

[DanHeidinga]

@sxa Is there a blog post here at Adopt planned to communicate that builds will be drop support for CentOS6/RHEL6 and the corresponding glibc level change? If not, I can help draft something to drive awareness of this in the broader community.

It'll also help get any feedback from users that may indicate if there are other concerns with this change.

[aahlenst]

@DanHeidinga Currently no plans for a dedicated blog post. If it's only for 15, it's probably going to be a part of the release announcement. If we want to switch across the board and are looking for feedback beforehand, we should do a separate blog post. If I recall the TSC discussion correctly, we haven't come to a conclusion, yet, what exactly we should do.

[sxa]

Some stats from the Fedora repositories - EPEL for v6 is still above v8, and about 1/6 of that of v7:
https://admin.fedoraproject.org/mirrormanager/statistics/2020-06-23/repositories

[sxa]

We have an alternative mitigation for this, therefore closing