WaitForService functionality

[chadrockey]

Original author: mate.wol...@gmail.com (April 23, 2012 15:12:23)

Current problem:
There is no blocking call waiting for a service to become available.

What is the expected output?
A convenience method waitForService in DefaultNode (and the Node interface).

Please provide any additional information below.
Attached the changeset.

Original issue: http://code.google.com/p/rosjava/issues/detail?id=105

[bofetadas]

I was looking for the same functionality and eventually came up with a work-around.

Note for Android rosjava users:
I don't make use of ROSActivity or AppCompatROSActivity. These activities are good as entry point but for any more sophisticated development they restrict the programmer too much.
Look into here to find out how to get rid of ROSActivity.

Then, I grab a list of available topics with the below code. Every topic in the list has its publishers and subscribers attached to it, so by creating a set and adding all subscribers and publishers to that set, you eventually come up with a set of current running nodes.

val masterClient = MasterClient(masterUri)
val systemState = masterClient.getSystemState(GraphName.of("WHATEVER"))
val topicList = systemState.result.topics

Once I want to initialize and execute my service clients, I first have a look into the nodes set to figure out if the service server node is already up and running (assuming that a running service server node has also started its actual service server - I don't know if there's any way to find out about current services running.) If it isn't, I simply wait for 10 secs and then grab the set of nodes again and then try to initialize/execute the service client.

I know it's far from being as straight forward as python's wait_for_service function but it works.

Regards