ccmlib/scylla_node.py: use native scylla nodetool when it's available

in b18f85d, we use the native nodetool if JMX is not available, but
when running dtest from the local build, the jmx repo is still around,
so the java-based nodetool is picked. but the java-based nodetool does
not support tablets, and it would be great to always test the native
implementation built locally when testing using dtest without building
a relocatable package.

so, in this change, we go a step further by checking if the command line
of `scylla nodetool help` works, if it succeeds, we go ahead and use
`scylla nodetool`, otherwise, we fall back to the java-based nodetool.
we could instead use `scylla nodetool --help` instead of calling a
certain command of nodetool, but seastar returns 1 if `--help` is
used. a pull request was created to address it . see
scylladb/seastar#2213.

Signed-off-by: Kefu Chai <[email protected]>

ccmlib/scylla_node.py

@@ -776,16 +776,23 @@ def _update_jmx_pid(self, wait=True):
             self.jmx_pid = None
 
     def nodetool(self, cmd, capture_output=True, wait=True, timeout=None, verbose=True):
-        if not self.has_jmx:
+        try:
+            # nodetool subcommand was added in 5.5, so check if it is available
+            # before using it.
+            nodetool = [os.path.join(self.get_bin_dir(), "scylla"), "nodetool"]
+            subprocess.check_call(nodetool + ["help"], stdout=subprocess.DEVNULL, stderr=subprocess.STDOUT)
             if self.is_docker():
                 host = 'localhost'
             else:
                 host = self.address()
-            nodetool = [os.path.join(self.get_bin_dir(), "scylla"), "nodetool"]
             nodetool.extend(['-h', host, '-p', '10000'])
             nodetool.extend(cmd.split())
             return self._do_run_nodetool(nodetool, capture_output, wait, timeout, verbose)
+        except subprocess.CalledProcessError:
+            pass
 
+        # the java nodetool depends on JMX
+        assert self.has_jmx
         # Fall-back to the java nodetool for pre 5.5.0~dev versions, which don't yet have the native nodetool
         # Kill scylla-jmx in case of timeout, to supply enough debugging information