[ACCUMULO-4556] Monitor shows stack trace for NPE while viewing table details for accumulo.root if tablet is offline

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.7.1, 1.7.2, 1.8.0
• Fix Version/s: 2.0.0
• Component/s: monitor
• Labels: beginner
• Assignee: Unassigned
• Reporter: Sean Busbey
• Created: 05/Jan/17 11:24
• Updated: 19/Mar/18 17:59
• Resolved: 19/Mar/18 17:59

Description

AFAICT this is a problem in atleast 1.6.0 - current master (2.0-SNAPSHOT)

Noticed this while debugging a cluster with offline root tablet:

monitor -> Tables -> (shows accumulo.root with 1 offline tablet) -> accumulo.root ->

java.lang.NullPointerException
	at java.util.TreeMap.compare(TreeMap.java:1188)
	at java.util.TreeMap.put(TreeMap.java:531)
	at java.util.TreeSet.add(TreeSet.java:255)
	at org.apache.accumulo.monitor.servlets.TablesServlet.doTableDetails(TablesServlet.java:152)
	at org.apache.accumulo.monitor.servlets.TablesServlet.pageBody(TablesServlet.java:75)
	at org.apache.accumulo.monitor.servlets.BasicServlet.doGet(BasicServlet.java:65)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
	at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
	at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:401)
	at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
	at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:767)
	at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)
	at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
	at org.mortbay.jetty.Server.handle(Server.java:326)
	at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
	at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:928)
	at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:549)
	at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
	at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
	at org.mortbay.jetty.bio.SocketConnector$Connection.run(SocketConnector.java:228)
	at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)

Looking at master branch our handling in TablesServlet looks like

  private void doTableDetails(HttpServletRequest req, StringBuilder sb, Map<String,String> tidToNameMap, String tableId) {
    String displayName = Tables.getPrintableTableNameFromId(tidToNameMap, tableId);
    Instance instance = Monitor.getContext().getInstance();
    TreeSet<String> locs = new TreeSet<>();
    if (RootTable.ID.equals(tableId)) {
      locs.add(instance.getRootTabletLocation());
    } else {
...

The Instance API doesn't say it, but all of our current implementations return null for getRootTabletLocation when the root tablet is offline. Since we create locs with the empty constructor, it uses natural ordering and doesn't allow null members, so things explode.

Issue Links

• relates to: ACCUMULO-3005 Convert the monitor into a real REST server