/** * attempts to resolve hostnameTarget from origin * * @return null if it definitively can't be resolved, best-effort IP address if possible, or blank * if we could not run ssh or make sense of the output */ public static String getResolvedAddress( Entity entity, SshMachineLocation origin, String hostnameTarget) { ProcessTaskWrapper<Integer> task = SshTasks.newSshExecTaskFactory(origin, "ping -c 1 -t 1 " + hostnameTarget) .summary("checking resolution of " + hostnameTarget) .allowingNonZeroExitCode() .newTask(); DynamicTasks.queueIfPossible(task).orSubmitAndBlock(entity).asTask().blockUntilEnded(); if (task.asTask().isError()) { log.warn( "ping could not be run, at " + entity + " / " + origin + ": " + Tasks.getError(task.asTask())); return ""; } if (task.getExitCode() == null || task.getExitCode() != 0) { if (task.getExitCode() != null && task.getExitCode() < 10) { // small number means ping failed to resolve or ping the hostname log.debug( "not able to resolve " + hostnameTarget + " from " + origin + " for " + entity + " because exit code was " + task.getExitCode()); return null; } // large number means ping probably did not run log.warn( "ping not run as expected, at " + entity + " / " + origin + " (code " + task.getExitCode() + "):\n" + task.getStdout().trim() + " --- " + task.getStderr().trim()); return ""; } String out = task.getStdout(); try { String line1 = Strings.getFirstLine(out); String ip = Strings.getFragmentBetween(line1, "(", ")"); if (Strings.isNonBlank(ip)) return ip; } catch (Exception e) { Exceptions.propagateIfFatal(e); /* ignore non-parseable output */ } if (out.contains("127.0.0.1")) return "127.0.0.1"; return ""; }