rosbag record: Option for TCP_NODELAY

[alspitz]

When recording large messages such as Odometry, the messages arrive at the bag in clumps. It would be nice if rosbag record had a --tcpnodelay or --udp option to prevent this from happening.

[dirk-thomas]

The TCP_NODELAY option is a publisher setting. But in the case of recording rosbag is subscribing to the topics. Therefore it can't enforce / request that option.

Therefore I don't think this feature request for rosbag is feasible. Instead whichever node is publishing the odometer messages would need to provide that option.

[alspitz]

It's definitely an option that can be added to a C++ subscription: https://docs.ros.org/api/roscpp/html/classros_1_1TransportHints.html. AFAIK, there is no way to add transport hints to a C++ publisher.

[alspitz]

Also, since Python subscribers can also specify TCP_NODELAY (but not UDP), it would be nice if rostopic hz had a --nodelay option as well.

[dirk-thomas]

Sorry, you are right. The option can also be requested from the subscriber side.

Please consider to provide a pull request to add such an option to the rosbag record command.

[alspitz]

I've created a pull request here: #1295

[alspitz]

I also created a pull request for adding TCP_NODELAY to rostopic hz and delay here: #1296

[dirk-thomas]

I close this issue in favor of the pending PR #1295 (to only have one open item). Thank you for working on this.