Create code for Objective Error observer

[marioney]

Observer for Objective error: needed for scenarios 3 in yellow table

• Should check if there's an error when the route is not available.
  - Path length 0
• Check move_base/result topic
• Should check if the robot is blocked (not moving after X seconds)

Objective should publish: "true" if there's an error
"false" if the system is running OK.

Also create another another observer on the rosgraph_observer to send it to the reasoner

https://docs.google.com/document/d/1BaOxo7_WQ2fUUUWIyw5pE_K_q6sErQJXge5VeFjyhgQ/edit#bookmark=id.4rg7xmp249au

[marioney]

@darkobozhinoski @chcorbato A quick question, if an error is received, the message is sent but when should we clear the objective error (change the error message to false again)

Options are:

• When a new goal (reconfiguration) is received
• Only send the error one time
• Keep the error for X seconds

[marioney]

Done in 87ad4e0 and rosin-project/rosgraph_monitor@674fc29

* Keep the error for X seconds

For now the error message is published for 1 sec.

[chcorbato]

@darkobozhinoski @chcorbato A quick question, if an error is received, the message is sent but when should we clear the objective error (change the error message to false again)

I am not sure.

Options are:

• When a new goal (reconfiguration) is received
• Only send the error one time
• Keep the error for X seconds

Nice analysis. I would say the error should be reported while the condition that triggered it continuous. If the topics whose values cause it keep reporting the same values, keep sending the error. But it is just an idea.

[marioney]

Done in 87ad4e0 and rosin-project/rosgraph_monitor@674fc29

@chcorbato should we close this?

[chcorbato]

I think I remember seeing the error in the printout of the message received by mros1_reasoner with "ojbective" misspelled. A part from that, yes, you can close it.

[chcorbato]

This issue was completed, improvement tracked in meta-control/mc_mros_reasoner#94