[8u] RFR: 8059038: Create new launcher for SA tools

[Severin Gehwolf]

On Wed, 2018-12-12 at 16:18 +0000, Andrew Hughes wrote:
> On Wed, 12 Dec 2018 at 14:10, Severin Gehwolf <sgehwolf at redhat.com> wrote:
> > 
> > Hi,
> > 
> > Can I get a review of this small 8u enhancement, please? It adds two
> > new launchers for the serviceability agent, one CLI version and one GUI
> > version:
> > 
> > $ <image>/bin/clhsdb
> > $ <image>/bin/hsdb
> > 
> > The enhancement request has been approved here:
> > http://mail.openjdk.java.net/pipermail/jdk8u-dev/2018-December/008257.html
> > 
> > During that discussion it has been suggested to use separate launchers
> > for GUI and CLI. So this is the revised two-launcher-approach:
> > webrev: http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8059038/02/
> > bug: https://bugs.openjdk.java.net/browse/JDK-8059038
> > 
> > Note: The initial version of this patch[1] had one launcher "jhsdb"
> > with sub-commands "hsdb" and "clhsdb" delegating to the old launcher
> > classes.
> > 
> > The patch has two simple tests verifying that the launchers work.
> > Thoughts?
> > 
> > Thanks,
> > Severin
> > 
> > [1] http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8059038/01/
> > 
> 
> The patch itself looks ok. But it looks completely different from the
> changesets in 9:
> 
> https://hg.openjdk.java.net/jdk9/jdk9/jdk/rev/bf17c0a1c746
> https://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/24a8cbde76d8
> 
> Can you explain a little what's going on here?

Sure. The original patch for 9 added a new class, SALauncher, which
launches many of the original stand-alone commands from 8. jstack from
JDK 8, for example, became "jhsdb jstack" in 9+ via this class[I].

On the JDK 8 enhancement request approval thread a suggestion was made
for the backport to JDK 8 to mimic the stand-alone launcher approach
JDK 8 uses: "jstack" over "jhsdb jstack". So "clhsdb" (JDK 8) will be a
separate launcher over "jhsdb clhsdb" in JDK 9+.

The first webrev[1] above, mimic'ed JDK 9+, but not quite since it
didn't change the arguments and options. jhsdb clhsdb --pid <pid> (JDK
9+) vs. jhsdb clhsdb <pid> (in [1]).

That's basically the reason why the JDK 8 backport looks this
different. Of course we can also go with the original version[1], but
so far I've heard two +1's for the second version... Hence, I'm
proposing that version.

Thanks,
Severin

[I] https://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/24a8cbde76d8#l2.213