app: node: Add raft snapshot parameter options

[MathieuBordere]

This PR uses the new dqlite API dqlite_node_set_snapshot_params available from dqlite 1.8.0.

I want to update the SONAME of dqlite from libdqlite.so.0 to libdqlite.so.1 so that go-dqlite binaries built against a version of dqlite that contain this API fail when ran against an older version of the dqlite library. The problem is, I already released a version of libdqlite with SONAME libdqlite.so.0 that contains the dqlite_node_set_snapshot_params functionality.

I'm not entirely sure if I should:
a) make a new dqlite release 1.9.0 and update the SONAME ? <-- This probably seems most reasonable
b) just update the SONAME on master and not make a release ?
c) ... ?

[stgraber]

@MathieuBordere hmm, to me moving from libdqlite.so.0 to libdqlite.so.1 would normally be the sign of an API break, not simple symbol addition.

Unless we need to move to libdqlite.so.1 so that SEMVER works properly and then lets us do libdqlite.so.1.1.0, libdqlite.so.1.2.0, ... in the future and the same isn't currently true with libdqlite.so.0.

[MathieuBordere]

@MathieuBordere hmm, to me moving from libdqlite.so.0 to libdqlite.so.1 would normally be the sign of an API break, not simple symbol addition.

Unless we need to move to libdqlite.so.1 so that SEMVER works properly and then lets us do libdqlite.so.1.1.0, libdqlite.so.1.2.0, ... in the future and the same isn't currently true with libdqlite.so.0.

I'll experiment some more with it, I need libtool to somehow spit out a libdqlite.so.0.1 SONAME for it to work properly I think.

[MathieuBordere]

@stgraber So there's the -Wl,-z,relro,-z,now linker option to fail the loading of a binary containing unknown symbols, but go only allows setting them when explicitly allowed through the environment variable CGO_LDFLAGS_ALLOW, so go get will fail when users haven't set this environment variable.

There's another alternative, link but that doesn't seem to be available on all platforms, so some more configuration magic would be needed in libraries that want to use this and it won't work immediately, it will work once 2 versions of the library have applied this method.

There's no clear winning alternative for me, what would you prefer?

[stgraber]

@MathieuBordere I think if we can tweak the Makefile in lxd that may be good enough.

[MathieuBordere]

Let me have a look at those TestIntegration_ExecBindError failures, they only started coming up recently.

[MathieuBordere]

@MathieuBordere I think if we can tweak the Makefile in lxd that may be good enough.

Adapting export CGO_LDFLAGS_ALLOW="-Wl,-wrap,pthread_create" to something like export CGO_LDFLAGS_ALLOW="(-Wl,-wrap,pthread_create)|(-Wl,-z,now)" should do the trick normally.

[MathieuBordere]

test/roles.sh is hanging a bit more than expected, want to make sure it's not related to this change in any way.