Hi Till, thanks for the feedback! These endpoints are only called when the vertex is selected in the UI, so there should be any heavy RPC load. For back-pressure, we only sample top 3 calls of the stack (depth = 3). For the flame-graph, we want to sample the whole stack trace and we need different sampling rate (longer period, more samples). Those are the main reasons to split these in two "trackers", but I may be missing something.
I've prepared a little demo, so others can have a better idea of what I have in mind. https://youtu.be/GUNDehj9z9o Please note that this is a proof of concept and I'm not frontend person, so it may look little clumsy :) D. On Thu, Aug 1, 2019 at 11:40 AM Till Rohrmann <trohrm...@apache.org> wrote: > Hi David, > > thanks for starting this discussion. I like the idea of improving insights > into Flink's execution and I believe that a flame graph could be helpful. > > I quickly glanced over your changes and I think they go in a good > direction. One idea could be to share the `StackTraceSample` produced by > the `StackTraceSampleCoordinator` between the different > `StackTraceOperatorTracker` so that we don't send multiple requests for the > same operators. That way we would decrease a bit the RPC load. > > Apart from that, I think the next steps would be to find a committer who > could shepherd this effort and help you with merging it. > > Cheers, > Till > > On Wed, Jul 31, 2019 at 7:05 PM David Morávek <d...@apache.org> wrote: > > > Hello, > > > > While looking into Flink internals, I've noticed that there is already a > > mechanism for stack-trace sampling of a particular job vertex. > > > > I think it may be really useful to allow user to easily render a cpu > > flamegraph <http://www.brendangregg.com/flamegraphs.html> in a new UI > for > > a > > selected vertex (new tab next to back pressure) of a running job. Back > > pressure tab already provides a good idea of which vertex causes trouble, > > but it's hard to say what's actually going on. > > > > I've tried to implement a basic REST endpoint > > < > > > https://github.com/dmvk/flink/commit/716231822d2fe99004895cdd0a365560479445b9 > > >, > > that prepares data for the flame graph rendering and it seems to be > > providing good insight. > > > > It should be straightforward to render data from the endpoint in new UI > > using existing <https://github.com/spiermar/d3-flame-graph> javascript > > libraries. > > > > WDYT? Is this worth pushing forward? > > > > D. > > >
