title: Getting java.lang.IllegalStateException: block()/blockFirst()/blockLast() are blocking, which is not supported in thread single-1"
body: <p>I have a question . I am getting the mentioned error in the below code where i am doing in line where i am calling block() function. This error is intermittent. What could be the reason why this issue is visible in only few cases and running properly in other calls . What should be done here ?</p>
  <pre><code>@Override
  public Publisher&lt;AuthenticatedSigninRequestMessage&gt; apply(ServerWebExchange t, ExternalLoginInputDto u) {
      try {
          Mono&lt;ProviderDto&gt; providerDto = providerService.getProvider(u.getProvider());
          ProviderDto provider = providerDto.block();
          return externalAutheticationServices.get(provider.getService()).authenticateUser(u, provider);
      } catch (Throwable ex) {
          return Mono.error(ex);
      }
  }
  </code></pre>