Uploaded image for project: 'C++ Driver'
  1. C++ Driver
  2. CXX-2289

Can't use resume_token after program restart

XMLWordPrintableJSON

      Hello,

      I have an issue with change_streams and resume_tokens.
      Here is my use case : I have a server that read a collection and uses change_stream to sync to it. it uses a specific thread that has a while loop that constantly reads the change_stream.

      while (true)
{
  auto changeStream = collection.watch(changeStreamPipeline);
  if(changeStream.begin() != changeStream.end())
  {
    for(const auto& change : changeStream)
    {
      auto document = change["fullDocument"].get_document();
      std::string jsonChangeString = bsoncxx::to_json(document);
      resumeToken = changeStream.get_resume_token();
      /* Compute index */
    }
  }
}

      Where resumeToken is a class member.

       

       

      Then the resume token is saved as a string. in a struct called indexer_data

       

      boost::archive::binary_oarchive         archive(ofs);
IndexerData                             indexer_data;

std::string data = bsoncxx::to_json(_lastResumeToken.get());
indexer_data.lastResumeToken   = data;

archive << indexer_data;

       

       

      Then when the server restart the archive is read and we try to resume the stream from the resumeToken

       

      mongocxx::pipeline changeStreamPipeline;
changeStreamPipeline.match(bsoncxx::builder::basic::make_document(bsoncxx::builder::basic::kvp("operationType", "insert")));
mongocxx::options::change_stream changeStreamOptions;
if(!savedResumeToken.empty())
{
  auto resumeToken = bsoncxx::from_json(savedResumeToken);
  changeStreamOptions.resume_after(resumeToken);
}


auto changeStream = collection.watch(changeStreamPipeline, changeStreamOptions); // CRASH HERE

/* Loop to get the changes from the change stream */

      When we try to watch the collection with the options with the resumeToken, there is a crash, a SEGFAULT.
      Is it a known bug, do I use the resume_token the wrong way ?
      Note that it also happens if the resume_token is passed with the "start_after" option.

      Thanks in advance

       

       

            Assignee:
            ezra.chung@mongodb.com Ezra Chung
            Reporter:
            maxime.guillem@systrangroup.com Maxime Guillem
            Votes:
            1 Vote for this issue
            Watchers:
            6 Start watching this issue

              Created:
              Updated:
              Resolved: