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Add debug tips to README.md (#137)

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Dan Rose 2020-04-16 19:10:29 -05:00 • committed by GitHub
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@ -7,23 +7,55 @@ Cyclone DDS is ready to use. It seeks to give the fastest, easiest, and most rob
1. Install:
```
apt install ros-eloquent-rmw-cyclonedds-cpp
```
or
```
apt install ros-dashing-rmw-cyclonedds-cpp
```
```
apt install ros-eloquent-rmw-cyclonedds-cpp
```
or
```
apt install ros-dashing-rmw-cyclonedds-cpp
```
2) Set env variable and run ROS2 apps as usual:
2. Set env variable and run ROS2 apps as usual:
```export RMW_IMPLEMENTATION=rmw_cyclonedds_cpp```
```export RMW_IMPLEMENTATION=rmw_cyclonedds_cpp```
3) Confirm RMW: In Eloquent, to confirm which RMW you're using:
3. Confirm RMW: In Eloquent and later, to confirm which RMW you're using:
```ros2 doctor --report```
## Performance recommendations
With large samples (100s of kilobytes), excessive latency can be caused by running out of space in the OS-level receive buffer. For this reason, on Linux, we recommend increasing the buffer size:
* Temporarily (until reboot): `sudo sysctl -w net.core.rmem_max=8388608 net.core.rmem_default=8388608`
* Permanently: `echo "net.core.rmem_max=8388608\nnet.core.rmem_default=8388608\n" | sudo tee /etc/sysctl.d/60-cyclonedds.conf`
## Debugging
So Cyclone isn't playing nice or not giving you the performance you had hoped for? That's not good... Please [file an issue against this repository](https://github.com/ros2/rmw_cyclonedds/issues/new)!
The `ddsperf` tool distributed with Cyclone DDS can be used to check that communication works *without* ROS. Run `ddsperf sanity` on two different machines - if the "mean" value is above `100000us`, there are likely network issues.
If you're having trouble with nodes discovering others or can't use multicast *at all* on your network setup, you can circumvent discovery:
`export CYCLONEDDS_URI='<Discovery><Peers><Peer Address='myroshost.local' /><Peer Address='myroshost2.local' /></></>'`
Here are some ways to generate additional debugging info that can help identify the problem faster, and are helpful on an issue ticket:
* Configure Cyclone to create richer debugging output:
* To see the output live:
`export CYCLONEDDS_URI='<Tracing><Verbosity>trace</><Out>stderr</></>'`
* To send to `/var/log/`:
`export CYCLONEDDS_URI='<Tracing><Verbosity>trace</><Out>/var/log/cyclonedds.${CYCLONEDDS_PID}.log</></>'`
* Create a Wireshark capture:
`wireshark -k -w wireshark.pcap.gz`
## Building from source and contributing
The following branches are actively maintained: