Zc-wait-to-stop process name in v5.1.0

opacey · July 12, 2022, 4:30pm

Hi, After upgrading from v5.0.0 too v5.1.0 I’ve noticed that the daemon (i.e. viewed from top or ps) changes name from zcashd to zc-wait-to-stop after a few minutes then stays like that. The deamon continues to run indefinitely, verifying new blocks as normal.

Seems to be related to a shutdown call, as referenced here:

github.com

zcash/zcash/blob/4ae67b01f6185e3412a67e8f98aed1388ef99b93/src/bitcoind.cpp#L48


      
          * \section Navigation
          * Use the buttons <code>Namespaces</code>, <code>Classes</code> or <code>Files</code> at the top of the page to start navigating the code.
          */
          
          
static bool fDaemon;
          
          
void WaitForShutdown(boost::thread_group* threadGroup)
          {
             // This is the main process thread, but after this point, all we do here is wait for
             // shutdown, and then shut down the node.
             RenameThread("zc-wait-to-stop");
          
          
   bool fShutdown = ShutdownRequested();
             // Tell the main threads to shutdown.
             while (!fShutdown)
             {
                 MilliSleep(200);
                 fShutdown = ShutdownRequested();
             }
             if (threadGroup)
             {

…but not clear why the shutdown doesn’t proceed. The host is low on spare resources so I might expect the OS to kill the process but the rest of the behaviour is unexpected.

str4d · July 12, 2022, 4:39pm

This was me misunderstanding the effect of renaming the main thread. I presumed that all threads would be treated equally underneath the process, and made this change to improve debugging crashes (since after this point the only thing the main thread does is “wait for the node to shut down”). However, it turns out that the main thread is what gets used for naming the process in various tools, rather than the process name. There’s a PR open to fix this, which will be in the next release.

opacey · July 12, 2022, 4:43pm

I see! Thanks for the explanation and prompt reply.

I have a monitoring script which is why I noticed it - the script thinks the process has terminated. I’ll leave it and wait for the next release package. Thanks again!