Which guarantees, if any, do messages provide?

[Lukas Haase]

Hello,

I am currently trying to use messages as part of my signal chain and facing 
some obstacles.

For example, I use "Message Strobe" to create a message every 10ms. A custom 
blocks creates a pulse when the message is received (it does so by putting the 
message into a std::queue in the message handler and retrieving it in the work 
function).
When I trigger on one pulse and zoom out, I ideally would see one pulse exactly 
every 100ms. However, the pulses jump around (i.e., the period always changes).

Similarly, I create 2 of these custom blocks and sum their output signals. 
"Message Strobe" sends the same message to both blocks. Ideally the pulses 
would align perfectly and I would see one pulse. However, I see two pulses 
having a random delay (probably because the message arrives at different times 
at the blocks).

1.) What is the typical latency of messages?

2.) Related, what is typically the maximum speed for sending messages? Is 
sending messages at >1kHz (i.e., "Message Strobe" with interval <1ms) 
meaningful?

3.) Are there any "guarantees" on maximum/minimum delay? (for example, I read 
that the message handler is guaranteed to be executed when work() is not. Is an 
upper bound of delay (in samples) given by the worst case execution of the work 
function, i.e. the size of the output buffer?)

4.) Can I be sure that all messages are received or does gnuradio silently drop 
messages under certain conditions?

5.) Are messages always received in correct order?


Thanks,
Lukas