[lttng-dev] Lttng live protocol

Mathieu Desnoyers mathieu.desnoyers at efficios.com
Wed Sep 15 12:00:10 EDT 2021

----- On Sep 1, 2021, at 1:23 PM, lttng-dev <lttng-dev at lists.lttng.org> wrote: 

> Hi there,

> I am currently evaluating the use of CTF and lttng tooling for application
> tracing on windows. We are exploring alternatives to ETW that are more
> customisable.
> One thing we would really like to do is real-time monitoring of our application
> from another machine. I have a few questions regarding this:

> 1. Is lttng live protocol suitable for this purpose? What kind of latency would
> we expect? (e.g 10s or 100s of milliseconds or more)

The lttng live protocol has been designed for extracting a low-throughput of events to a live pretty-printer, with delays in the area of 
a few seconds. It's a polling-based mechanism at the moment. 

> 2. Is the protocol documented?

No. There is only an implementation with the lttng project and in babeltrace. 

> 3. Is it possible to use lttng-relayd to read from local CTF log files (which
> are being written to) and stream events to other machines / a viewer on the
> same machine? The reason I ask this is the documentation seems suggests
> lttng-relayd can consume CTF files [
> https://lttng.org/docs/v2.13/#doc-lttng-relayd |
> https://lttng.org/docs/v2.13/#doc-lttng-relayd ] .

lttng-relayd needs to control both writing to the CTF log files and reading from them. The "writing to" 
cannot be done by an external process. 

> 4. I see there is a windows cygwin build on jenkins. Would you recommend this
> for production use?

We do not recommend Cygwin builds for production use unless there are no alternatives. From my own 
past experience, the Cygwin layer is not a solid basis for production-quality software. 

Thanks for your interest, 


> Any guidance would be much appreciated.

> Thanks in advance,

> Mayur

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> Mayur Patel

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Mathieu Desnoyers 
EfficiOS Inc. 
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