链路追踪

// Hook into a callback provided by the RPC framework that is called on outgoing requests
public Response onOutgoingRequest(Request request) throws Exception {
  Span span = ElasticApm.currentSpan() 
          .startSpan("external", "http", null)
          .setName(request.getMethod() + " " + request.getHost());
  try (final Scope scope = transaction.activate()) {
      span.injectTraceHeaders((name, value) -> request.addHeader(name, value)); 
      return request.execute();
  } catch (Exception e) {
      span.captureException(e);
      throw e;
  } finally {
      span.end(); 
  }
}

// Hook into a callback provided by the framework that is called on incoming requests
public Response onIncomingRequest(Request request) throws Exception {
    // creates a transaction representing the server-side handling of the request
    Transaction transaction = ElasticApm.startTransactionWithRemoteParent(request::getHeader, request::getHeaders); 
    try (final Scope scope = transaction.activate()) { 
        String name = "a useful name like ClassName#methodName where the request is handled";
        transaction.setName(name); 
        transaction.setType(Transaction.TYPE_REQUEST); 
        return request.handle();
    } catch (Exception e) {
        transaction.captureException(e);
        throw e;
    } finally {
        transaction.end(); 
    }
}