docs: public static synchronized boolean registerIfAbsent(final Callable<Tracer> provider) {
          requireNonNull(provider, "Cannot register GlobalTracer from provider <null>.");
          if (!isRegistered()) {
              try {
                  final Tracer suppliedTracer = requireNonNull(provider.call(), "Cannot register GlobalTracer <null>.");
                  if (!(suppliedTracer instanceof GlobalTracer)) {
                      GlobalTracer.tracer = suppliedTracer;
                      isRegistered = true;
                      return true;
                  }
              } catch (RuntimeException rte) {
                  throw rte; // Re-throw as-is
              } catch (Exception ex) {
                  throw new IllegalStateException("Exception obtaining tracer from provider: " + ex.getMessage(), ex);
              }
          }
          return false;
      }