[lttng-dev] Proposal: Make lttng-analyses part of lttng-tools

[Geneviève Bastien]

Hi all,


Here's an idea to improve first impression of lttng and hopefully help
the UX of the toolchain:


tl;dr; I propose to make lttng-analyses part of lttng-tools to provide
some basic recording/analysis facilities and make them the blessed way
of getting started with lttng, so that end users can quickly obtain
meaningful results after installing lttng.

Here follows my argumentation. I'll focus on kernel tracing.


Facts:

* People don't read documentation, at least not from the beginning.

* First impressions stick

* Potential users trying to evaluate a tool will typically spend a few
minutes/hours getting that first impression by reading an as
minimalistic as possible readme file.


Right now, with lttng, the first thing people are invited to do for
kernel tracing, is to enable all the events (-a -k), which results in a
number of lost events and a lot of noise when trying to analyze the
results, and then 'lttng view' to display the babeltrace output! (see
the Usage section in the lttng-modules readme page here:
https://github.com/lttng/lttng-modules)

That is not imho a good first impressions. Other tracers like ftrace or
perf have a more per-event approach to tracing, their beginner's
documentation showing how to enable 1 or 2 tracepoints. But to get
interesting results, we usually need more than that and listing them
individually can be cumbersome. Looking at my outbox, I sent my lttng
script to enable events to get the critical path to at least 15 people
in the last years... It would be easy to have a predefined script for
that purpose. Or many scripts (or profiles?) to enable events for
various interesting analyses types.

By comparison, take another kernel tracing tool: ebpf / bcc
(https://github.com/iovisor/bcc). Installation is easy, then the readme
points to a number of tools and example scripts of all kind. Running
them after installation is easy and gives instant results. That makes
one happy and feel good about bcc! Because having to write an ebpf
script would have many users run for their sanity! ;-) But since many
use cases are already covered by easily available scripts, people adopt
the tool, then a few months later, when they need more, some may get to
actually read the script, modify it, make them own.

lttng should aim for that kind of ease of use for beginners, have them
reach that good feeling in a few minutes trial. And lttng-analyses
already provides such scripts to record and analyze traces, and it
should really be put forward and improved to give the user a more
seamless first experience. I'd suggest to include it with lttng-tools,
in a tools/ directory, as it would be one less repo to fork or one less
package to install and it's a clear sign that it goes together with
lttng. Keeping it as a separate project makes it appear as a side-dish,
while it should be the center-plate!


What do you think?

Regards,

Geneviève