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https://github.com/clojure-goes-fast/clj-async-profiler
Embedded high-precision Clojure profiler
https://github.com/clojure-goes-fast/clj-async-profiler
clojure flamegraphs profiling
Last synced: 7 days ago
JSON representation
Embedded high-precision Clojure profiler
- Host: GitHub
- URL: https://github.com/clojure-goes-fast/clj-async-profiler
- Owner: clojure-goes-fast
- Created: 2017-12-11T13:37:16.000Z (about 7 years ago)
- Default Branch: master
- Last Pushed: 2024-05-18T20:37:52.000Z (9 months ago)
- Last Synced: 2024-05-18T21:29:35.084Z (9 months ago)
- Topics: clojure, flamegraphs, profiling
- Language: Clojure
- Homepage: http://clojure-goes-fast.com/kb/profiling/clj-async-profiler/
- Size: 4.55 MB
- Stars: 379
- Watchers: 10
- Forks: 17
- Open Issues: 4
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
Awesome Lists containing this project
- awesome-clojure-repl - clj-async-profiler
README
# clj-async-profiler [](https://dl.circleci.com/status-badge/redirect/gh/clojure-goes-fast/clj-async-profiler/tree/master)  [](https://clojars.org/com.clojure-goes-fast/clj-async-profiler)  [](CHANGELOG.md)
**clj-async-profiler** is an embedded high-precision performance profiler for
Clojure. No need to install anything on your system — just add a single
dependency to your project to operate the profiler either programmatically or
via a web UI. The profiling overhead is very low, so it can be used even in
highly loaded production scenarios.
clj-async-profiler presents the profiling results as an interactive flamegraph.
You can navigate the flamegraph, query it, change parameters and adapt the
results for easier interpretation.
Example flamegraph. Click to open the interactive version.
To collect the profiling data, clj-async-profiler utilizes
[async-profiler](https://github.com/async-profiler/async-profiler) which is
a low overhead sampling profiler for Java. Current version of async-profiler
that is used by clj-async-profiler is
[3.0](https://github.com/async-profiler/async-profiler/releases/tag/v3.0).
## Usage
> [!TIP]
> Comprehensive usage guide and in-depth documentation are available at [Clojure
Goes Fast knowledge
base](http://clojure-goes-fast.com/kb/profiling/clj-async-profiler/).
clj-async-profiler has the following requirements:
- Linux or MacOS
- JDK 1.8+. Note that clj-async-profiler requires **JDK**, it won't run on
[JRE](https://www.digitalocean.com/community/tutorials/difference-jdk-vs-jre-vs-jvm).
- Clojure 1.10+
On Linux, you need to allow async-profiler to use kernel profiling data by
setting these two variables ([see
also](https://github.com/async-profiler/async-profiler#basic-usage)):
```
sudo sysctl -w kernel.perf_event_paranoid=1
sudo sysctl -w kernel.kptr_restrict=0
```
Next, add `com.clojure-goes-fast/clj-async-profiler` to your dependencies. This
is the latest version:
[](https://clojars.org/com.clojure-goes-fast/clj-async-profiler)
On **JDK 11** and later, you must start your application with JVM option
`-Djdk.attach.allowAttachSelf`, otherwise the profiling agent will not be able
to dynamically attach to the running process.
- With tools.deps, add `:jvm-opts ["-Djdk.attach.allowAttachSelf"]` to an alias
in `deps.edn` and enable that alias, or add `-J-Djdk.attach.allowAttachSelf`
explicitly to your REPL command.
- With Leiningen, add `:jvm-opts ["-Djdk.attach.allowAttachSelf"]` to `project.clj`.
`clj-async-profiler.core` exposes an all-in-one facade for generating profiling
flame graphs. The most common usage scenario looks like this:
```clojure
(require '[clj-async-profiler.core :as prof])
;; Profile the following expression:
(prof/profile (dotimes [i 10000] (reduce + (range i))))
;; The resulting flamegraph will be stored in /tmp/clj-async-profiler/results/
;; You can view the HTML file directly from there or start a local web UI:
(prof/serve-ui 8080) ; Serve on port 8080
```
You can also start and stop the profiler manually with `prof/start` and
`prof/stop`.
Each profiling command accepts a map of options. See docstrings for each command
for the list of supported options, or [Functions and
options](http://clojure-goes-fast.com/kb/profiling/clj-async-profiler/basic-usage/#functions-and-options).
Option map for each profiling command can have a `:pid` value. If it is
provided, an external JVM process with this PID will be sampled, otherwise the
current process is targeted.
For a detailed description of clj-async-profiler's advanced features, see the
documentation pages:
- [Exploring flamegraphs](https://clojure-goes-fast.com/kb/profiling/clj-async-profiler/exploring-flamegraphs/)
- [Allocation profiling](http://clojure-goes-fast.com/kb/profiling/clj-async-profiler/allocation-profiling/)
- [Differential flamegraphs](http://clojure-goes-fast.com/kb/profiling/clj-async-profiler/diffgraphs/)
- [Startup profiling](http://clojure-goes-fast.com/kb/profiling/clj-async-profiler/startup/)
- [Profiling in production](http://clojure-goes-fast.com/kb/profiling/clj-async-profiler/production/)
Also check out this video from London Clojurians meetup:
[](http://www.youtube.com/watch?v=s3mjVAMNVrA "Clojure Goes Brrr: a quest for performance")
### Sharing flamegraphs
A flamegraph is a fully self-contained HTML file that is saved into
`/tmp/clj-async-profiler/results/` directory. This file can be sent to somebody
else and opened in the browser. It can also be uploaded to any hosting that
allows serving HTML pages.
clj-async-profiler offers out-of-the-box integration with
[Flamebin](https://flamebin.dev/) — a website dedicated to storing and sharing
flamegraphs. You can use it like this:
```clj
;; Assuming that you have already captured a profile, and its ID=1. ID is the
;; number that comes after the date in flamegraph's filename. Alternatively, you
;; can provide the full path to the captured .txt profile.
=> (require '[clj-async-profiler.flamebin :as flamebin])
=> (flamebin/upload-flamegraph 1 {})
;; Uploaded /tmp/clj-async-profiler/results/20241120_181404-01-cpu-collapsed.txt to Flamebin.
;; Share URL: https://flamebin.dev/Y8Gwjh?read-token=xU8wRrZJgXtwkfT0j9
;; Deletion URL: https://flamebin.dev/api/v1/delete-profile?id=Y8Gwjh&edit-token=...
;; Private uploads don't show on the index page. Private profiles can only be decrypted by providing read-token. The server doesn't store read-token for private uploads.
```
The code above uploads the flamegraph to Flamebin and gives you a link you can
share with your colleagues. By default, it creates a **private** Flamegraph, so
a read-token must be provided to view the flamegraph. If you capture a
flamegraph of an open-source project and plan to share it publicly (e.g.,
adding it to a bug report/PR), you can opt for a public flamegraph:
```clj
=> (flamebin/upload-flamegraph 1 {:public? true})
;; Uploaded /tmp/clj-async-profiler/results/20241120_181404-01-cpu-collapsed.txt to Flamebin.
;; Share URL: https://flamebin.dev/RibWCt
;; Deletion URL: https://flamebin.dev/api/v1/delete-profile?id=RibWCt&edit-token=...
```
Note that the URL is shorter as read-token is no longer present.
It is also possible to upload diffgraphs using
`clj-async-profiler.flamebin/upload-diffgraph`. You need to provide two profiles
(before and after) in the same manner as to `generate-diffgraph`.
### Tuning for better accuracy
From [async-profiler
README](https://github.com/async-profiler/async-profiler#restrictionslimitations):
It is highly recommended to use `-XX:+UnlockDiagnosticVMOptions
-XX:+DebugNonSafepoints` JVM flags. Without those flags the profiler will still
work correctly but results might be less accurate. Without these options, there
is a high chance that simple inlined methods will not appear in the profile.
When agent is attached at runtime, CompiledMethodLoad JVMTI event enables debug
info, but only for methods compiled after the event is turned on.
If you see stackframes like `/usr/lib/.../libjvm.so` in the flamegraph, it means
that you have to install JDK debug symbols. E.g., on Ubuntu that would be the
package `openjdk-11-dbg`.
### Output directory
By default, clj-async-profiler writes its output files to
`/tmp/clj-async-profiler/`. You can change it to a custom directory (e.g., if
you run clj-async-profiler in an environment where `/tmp` is not sufficiently
large) by setting Java property `clj-async-profiler.output-dir`:
`clojure -J-Dclj-async-profiler.output-dir=./data ...`
## Troubleshooting
### Error: Can not attach to current VM
Most likely, you are missing `-Djdk.attach.allowAttachSelf` JVM option.
1. Add `-Djdk.attach.allowAttachSelf` to your `deps.edn` or `project.clj` as
described in [Usage
guide](https://github.com/clojure-goes-fast/clj-async-profiler?tab=readme-ov-file#usage).
2. Verify that the option is set correctly by running this in the REPL. The
command should return `""` (empty string). If it returns `nil`, there is
something wrong with how you set the allowAttachSelf option.
```clj
user=> (System/getProperty "jdk.attach.allowAttachSelf")
""
```
### WARNING: package jdk.attach not in java.base
You are trying to run clj-async-profiler with Java JRE. clj-async-profiler can
only work under Java **JDK**.
## Platform support
clj-async-profiler ships with the precompiled native libraries that
async-profiler itself
[distributes](https://github.com/async-profiler/async-profiler#download).
These include:
- **Linux**: x64, aarch64 (arm64)
- **MacOS**: x64/aarch64 (universal binary)
To use clj-async-profiler on other [supported
platforms](https://github.com/async-profiler/async-profiler#supported-platforms),
you should do the following:
1. Build
[async-profiler](https://github.com/async-profiler/async-profiler#building)
for the desired platform.
2. Put the resulting `libasyncProfiler.so` in a place accessible by your JVM
process (and which also allows code execution from).
3. Execute from Clojure:
```clj
(reset! prof/async-profiler-agent-path "/path/to/libasyncProfiler.so")
```
## Development
Regular build tasks are inside [build.clj](build.clj) and invoked as `clojure
-T:build test`, `clojure -T:build jar`, etc.
When starting a REPL, you should add `dev` alias on the list so that
[virgil](https://github.com/clj-commons/virgil) is loaded. Then, to compile Java
classes at the REPL, do:
```clojure
user> ((requiring-resolve 'virgil/compile-java) ["src"])
```
## License
clj-async-profiler is distributed under the Eclipse Public License. See
[ECLIPSE_PUBLIC_LICENSE](docs/ECLIPSE_PUBLIC_LICENSE).
Copyright 2017-2025 Oleksandr Yakushev
---
async-profiler is distributed under Apache-2.0. See
[APACHE_PUBLIC_LICENSE](docs/APACHE_PUBLIC_LICENSE) file. The location of the
original repository is
[https://github.com/async-profiler/async-profiler](https://github.com/async-profiler/async-profiler).
Copyright 2017-2025 Andrei Pangin