Is it possible to publish/subscribe large data?

[ghost]

I'm trying to HelloWorld examples which connect to FastRTPS and publish/subscribe large data.
But client cannot publish/subscribe data.

Environment

OS: Ubuntu 16.04
Following examples execute in PC:

subscriber: FastRTPS example
HelloWorldExample  
      |  
micro RTPS agent  
      |  
publisher: micro RTPS client example  
PublishHelloWorld  

And I changed the micro-RTPS-client example.
Below is my code:

micro-RTPS-client/examples/PublishHelloWorld/main.c

114        topic.message = "AAAAA.................";　// over 500 characters

Results

I captured network packets (wireshark) but client didn't send messages.

What am I doing wrong? configuration is wrong or memory problem?
Thanks for the help.

[julionce]

Hi @muto-esol,
There is a MTU size (512 bytes by default) which limits the maximum message size. In order to increase this MTU, you have to modified the CONFIG_MAX_TRANSMISSION_UNIT_SIZE define in transport/config.h for both Agent and Client. As well as modified the MICRORTPS_MTU_SIZE define in xrce_client.h. Please let's me known if it works for you.

[julionce]

Hi @muto-esol,
We have just launched a new release 1.0.0beta2 in which we are improved the MTU selection. I close the issue, in case of persistence reopen the issue.

[ghost]

Hello there,
I tried to increase the MTU for UDP by setting

• on the client side inside client.config: CONFIG_UDP_TRANSPORT_MTU=1024
• on the agent side inside CMakeLists.txt: CONFIG_UDP_TRANSPORT_MTU=1024

Then I built both and tried to run the agent and two clients, but I always get
serialize eprosima::fastcdr::exception::NotEnoughMemoryException

am I missing something?

[julionce]

Hi @torave,

Your error is due to the MTU of the output packets from the Agent to the Client, you can solve it change the mtu_size in OutputMessage.h. As you can see there is a related TODO which we are going to solve for next release which will be available in the next weeks. I hope it helps you.

[ghost]

Good morning @julianbermudez ,

thank you very much, this solved the problem!
However, when I increase the mtu size, the agent gives me a Segmentation fault (core dumped)
. A value of 2048 works perfectly fine, but anything above 3000 seems to be problematic. I'm not sure where this error originates -does it have to do with an underlying layer or may my system be the problem?

[julionce]

Hi @torave,

I will check it in order to give you an answer as soon as possible.

[julionce]

Hi @torave,

I checked and solved your issue on commit eProsima/Micro-XRCE-DDS-Agent@bd3967c.
Apart from this hotfix you should configure publisher and subscriber as is described in eProsima/Micro-XRCE-DDS-Agent#4 in order to send large data. This issue could be relate with #24.
Please check it and give me your feedback.
Thanks!

[ghost]

Hello @julianbermudez,

Sorry for my late answer, I've been sick.
I wanted to test the software, but I haven't actually been able to build. I cloned the master repository of the Micro-XRCE-DDS-Agent and followed the instructions on https://micro-xrce-dds.readthedocs.io/en/latest/installation.html. When I use the make command, I get the following output:

Scanning dependencies of target microxrcedds_agent
[  3%] Building CXX object CMakeFiles/microxrcedds_agent.dir/src/cpp/Root.cpp.o
[  6%] Building CXX object CMakeFiles/microxrcedds_agent.dir/src/cpp/processor/Processor.cpp.o
[ 10%] Building CXX object CMakeFiles/microxrcedds_agent.dir/src/cpp/client/ProxyClient.cpp.o
[ 13%] Building CXX object CMakeFiles/microxrcedds_agent.dir/src/cpp/participant/Participant.cpp.o
/home/tv/Projects/Micro-XRCE-DDS-Agent/src/cpp/participant/Participant.cpp: In member function ‘virtual bool eprosima::uxr::Participant::matched(const dds::xrce::ObjectVariant&) const’:
/home/tv/Projects/Micro-XRCE-DDS-Agent/src/cpp/participant/Participant.cpp:152:43: error: no match for ‘operator==’ (operand types are ‘eprosima::fastrtps::ParticipantAttributes’ and ‘const eprosima::fastrtps::ParticipantAttributes’)
     return parser_cond && (new_attributes == old_attributes);
                            ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
CMakeFiles/microxrcedds_agent.dir/build.make:134: recipe for target 'CMakeFiles/microxrcedds_agent.dir/src/cpp/participant/Participant.cpp.o' failed
make[2]: *** [CMakeFiles/microxrcedds_agent.dir/src/cpp/participant/Participant.cpp.o] Error 1
CMakeFiles/Makefile2:104: recipe for target 'CMakeFiles/microxrcedds_agent.dir/all' failed
make[1]: *** [CMakeFiles/microxrcedds_agent.dir/all] Error 2
Makefile:129: recipe for target 'all' failed
make: *** [all] Error 2

Should I open a new issue for this, since it isn't really related to the datasize affair?

[julionce]

Hi @torave,

There is a similar issue open, I redirect to it. Please tell me if you are able to solve this issue. Thanks!