7. Troubleshooting¶

This section covers a few issues you may run into while deploying your system with Cloud Discovery Service.

Note

All the issues addressed in this section assume that your applications would communicate directly with each other without Cloud Discovery Service.

7.1. My Applications don’t Communicate¶

There can be many reasons why your applications may not communicate with Cloud Discovery Service. Nevertheless, below are some of the common issues you may run into.

7.1.1. Make Sure Your Application can Accept Unknown Peers¶

For DomainParticipants to discover each other through Cloud Discovery Service, they require the ability to accept unknown peers. This is a Discovery QoS setting whose default value is true. Make sure your DomainParticipants are created with this value. For instance, you can add the following XML setting to the <participant_qos> element used by your application:

<discovery>
    <accept_unknown_peers>true</accept_unknown_peers>
</discovery>

7.1.2. Check that Your Initial Peers List Points to Cloud Discovery Service¶

Your applications are required to provide discovery information to Cloud Discovery Service. For that, they must know where Cloud Discovery Service is running. You provide this information through the initial peers list using an RTPS peer descriptor.

You can specify the initial peers list through the Discovery QoS ( programmatically, XML, or the environment). For instance, assuming a Cloud Discovery Service instance is running on UDP, port 7400 and host CDS_HOST:

Listing 7.1 XML¶

 <discovery>
     <initial_peers>
         <element>rtps@udpv4://CDS_HOST:7400</element>
     </initial_peers>
 </discovery>

Listing 7.2 Environment Variables¶

 export NDDS_DISCOVERY_PEERS=rtps@udpv4://CDS_HOST:7400

7.1.3. See Where Your Cloud Discovery Service Instance is Listening¶

To verify that Cloud Discovery Service is actually listening where you specified, you can run with -verbosity 4 and look for the following message:

...
[CDS DETECTOR] listening for announcements on:
    udpv4://172.17.0.2:10000
...

The message above indicates that Cloud Discovery Service is listening on the interface 172.17.0.2 over the UDP transport on port 10000.

Additionally, make sure the Cloud Discovery Service location is reachable from where your applications run.

7.2. Cloud Discovery Service Log Errors¶

This section shows a few of the errors that Cloud Discovery Service may show on startup.

7.2.1. Invalid Port¶

If an invalid port is specified, you may see this error log output:

...
NDDS_Transport_UDPv4_Socket_bindWithIp:OS bind() failure, error 0: Success
NDDS_Transport_UDPv4_Socket_bindWithIp:invalid port 70000
NDDS_Transport_UDPv4_SocketFactory_create_receive_socket:invalid port 70000
NDDS_Transport_UDP_create_recvresource_rrEA:!create socket
COMMENDLocalReaderRW_init:!create unicast entryPort
...

The messages above indicate an error binding a UDP socket to port 70000, which is out of the valid port range for this transport.

7.2.2. Port Already in Use¶

If a port that is already in use is specified, you may see this error log output:

...
NDDS_Transport_UDPv4_Socket_bindWithIp:0X1CE8 in use
NDDS_Transport_UDPv4_SocketFactory_create_receive_socket:invalid port 7400
NDDS_Transport_UDP_create_recvresource_rrEA:!create socket
COMMENDLocalReaderRW_init:!create unicast entryPort
...

The messages above indicate an error binding a UDP socket to port 7400, which is being used by other process.