This capability is disabled by default, it is driven by a system property you have to set to true in order to be able to get an instance of AsyncProfiler which does the actual profiling. If disabled, which is default, then any calls via nodetool which needs AsyncProfiler (start, stop, status) would return a message that profiling is not enabled.
Not sure if this answers your concerns but without knowingly turning it on nothing happens. On Wed, Dec 10, 2025 at 6:28 PM David Capwell <[email protected]> wrote: > > I have no issues adding it. I think my only real comment would be the same > as with manager; w/e we expose to the public api (in this case Nodetool) we > have to support, so if a 3rd party lib breaks compatibility that puts us in a > bind if we didn’t think about that up front. > > Having async-profiler exposed makes it easier to profile is a good thing. > Manager has (or is in the process of adding) API auth so we can lock down > async-profiler to those “allowed” but do we have similar in Nodetool? We had > an issue in the past that async-profiler would trigger a JVM crash (JVM bug), > so we had to limit calls to it until it was fixed. > > > On Dec 10, 2025, at 9:00 AM, Štefan Miklošovič <[email protected]> > > wrote: > > > > Worth to mention that we were also contemplating about the inclusion > > of jfr-convert so a user can also convert raw JFR files to e.g. HTML > > with heatmaps but we evaluated that it is not necessary. Sure, it > > would be comfortable, but ultimately not needed. Conversion of such a > > file via nodetool, on server side, is just not a good idea, it is not > > a job of a server to convert anything. > > > > In majority of cases, people using the profiler just want to get a > > HTML with cpu / allocation profile, it can even gather JFR files as > > such and fetch it is, it is just that the conversion as such can > > happen on client's side instead. > > > > I am +1 for introducing the core async profiler library only. > > > > On Wed, Dec 10, 2025 at 5:46 PM Bernardo Botella > > <[email protected]> wrote: > >> > >> Hi everyone! > >> > >> I’d like to propose adding the async-profiler library to the Cassandra > >> project. This will enable us to add a new nodetool command to do profiling > >> tasks on the process running Cassandra. This information can be useful to > >> debug a wide range of potential issues and performance optimizations. > >> CASSANDRA-20854 captures the effort and the details of the proposal, and > >> this PR proposes its implementation. > >> > >> I want to note that this feature was already discussed in this thread, and > >> this one only want to make sure that no one has any concerns about adding > >> the library as a dependency. > >> > >> What is async-profiler? > >> async-profiler is a low overhead sampling profiler for Java that does not > >> suffer from the Safepoint bias problem. It features HotSpot-specific API > >> to collect stack traces and to track memory allocations. The profiler > >> works with OpenJDK and other Java runtimes based on the HotSpot JVM. > >> > >> Unlike traditional Java profilers, async-profiler monitors non-Java > >> threads (e.g., GC and JIT compiler threads) and shows native and kernel > >> frames in stack traces. > >> > >> What can be profiled: > >> > >> CPU time > >> Allocations in Java Heap > >> Native memory allocations and leaks > >> Contended locks > >> Hardware and software performance counters like cache misses, page faults, > >> context switches > >> and more. > >> > >> > >> We propose to add async-profiler 4.2 as a dependency to Cassandra. > >> > >> Any concerns? > >> Bernardo >
