BTraceIO JBang Catalog

JBang distribution for BTraceIO tools, including Jafar and BTrace.

Quick Start

Option 1: Install from Catalog (Recommended)

# Add the catalog (one-time setup)
jbang catalog add --name btraceio https://raw.githubusercontent.com/btraceio/jbang-catalog/main/jbang-catalog.json

# Or use implicit resolution (no setup needed)
jbang jfr-shell@btraceio recording.jfr

BTrace (from this catalog)

# Run BTrace via the catalog alias
jbang btrace@btraceio <PID> <script.java>

Option 2: Direct Script Execution

# No setup required - just run the script URL
jbang https://raw.githubusercontent.com/btraceio/jbang-catalog/main/jfr-shell.java recording.jfr

Option 3: JitPack Coordinates

# Pin to specific version
jbang io.github.btraceio:jfr-shell:0.1.0 recording.jfr

# Latest development snapshot
jbang io.github.btraceio:jfr-shell:main-SNAPSHOT recording.jfr

Usage Examples

Interactive Mode

# Open JFR file in interactive shell
jbang jfr-shell@btraceio -f recording.jfr

# The shell provides tab completion and a REPL for JfrPath queries
jfr> show events/jdk.ExecutionSample | count()
jfr> show events/jdk.FileRead[bytes>1048576] | top(10, by=bytes)
jfr> help

Non-Interactive Mode

# Execute a single query
jbang jfr-shell@btraceio show recording.jfr "events/jdk.ExecutionSample | count()"

# Get JSON output for scripting
jbang jfr-shell@btraceio show recording.jfr \
  "events/jdk.FileRead | top(10, by=bytes)" \
  --format json

# Analyze thread activity
jbang jfr-shell@btraceio show recording.jfr \
  "events/jdk.ExecutionSample | groupBy(thread/name)"

# GC analysis
jbang jfr-shell@btraceio show recording.jfr \
  "events/jdk.GCHeapSummary[when/when='After GC']/heapSpace"

# List metadata
jbang jfr-shell@btraceio metadata recording.jfr --events-only

# Show chunks
jbang jfr-shell@btraceio chunks recording.jfr --summary

Install as Command

For repeated use, install jfr-shell as a permanent command:

# Install
jbang app install jfr-shell@btraceio

# Now use it like a native command
jfr-shell recording.jfr
jfr-shell show recording.jfr "events/jdk.ExecutionSample | count()"
jfr-shell --help

Available Aliases

• jfr-shell - Default, uses wrapper script (recommended)
• jfr-shell-jitpack - Version-pinned via JitPack (0.1.0)
• jfr-shell-latest - Latest main branch snapshot

JfrPath Query Language

JfrPath provides a concise, powerful way to query JFR data:

# Basic projection
events/jdk.FileRead/path

# Filtering
events/jdk.FileRead[bytes>1048576]

# Aggregations
events/jdk.ExecutionSample | count()
events/jdk.FileRead/bytes | sum()
events/jdk.FileRead/bytes | stats()

# Grouping
events/jdk.ExecutionSample | groupBy(thread/name)

# Top N
events/jdk.FileRead | top(10, by=bytes)

# Complex filters with functions
events/jdk.FileRead[contains(path, "/tmp/")]
events/jdk.ExecutionSample[len(stackTrace/frames)>20]

# Metadata exploration
metadata/jdk.types.StackTrace --tree
cp/jdk.types.Symbol
chunks --summary

See the JfrPath Reference for complete syntax.

Installation

JBang

If you don't have JBang installed:

# macOS/Linux
curl -Ls https://sh.jbang.dev | bash -s - app setup

# Windows (PowerShell)
iex "& { $(iwr https://ps.jbang.dev) } app setup"

# Or via package managers
brew install jbangdev/tap/jbang          # macOS (Homebrew)
sdk install jbang                        # SDKMAN
scoop install jbang                      # Windows (Scoop)
choco install jbang                      # Windows (Chocolatey)

JBang automatically downloads Java if needed, so you don't need a pre-installed JDK.

Documentation

• Main Repository - Full source code and build instructions
• JFR Shell Usage Guide - Complete feature overview
• JfrPath Reference - Query language grammar and operators
• JBang Documentation - JBang official docs

Requirements

• Java 26+ (JBang will download automatically if needed)
• JBang 0.100.0+

Features

• Interactive REPL with intelligent tab completion
• JfrPath query language for filtering, projection, and aggregation
• Multiple output formats: table (default) and JSON
• Multi-session support: work with multiple recordings simultaneously
• Non-interactive mode: execute queries from command line for scripting/CI
• Fast streaming parser: efficient memory usage, handles large recordings

Examples

Count Events by Type

jbang jfr-shell@btraceio show recording.jfr "events/jdk.ExecutionSample | count()"

Find Hot Methods

jbang jfr-shell@btraceio show recording.jfr \
  "events/jdk.ExecutionSample | groupBy(stackTrace/frames[0]/method/name/string) | top(10, by=count)"

Analyze File I/O

jbang jfr-shell@btraceio show recording.jfr \
  "events/jdk.FileRead | groupBy(path, agg=sum, value=bytes) | top(10, by=sum)"

Memory Statistics

jbang jfr-shell@btraceio show recording.jfr \
  "events/jdk.GCHeapSummary[when/when='After GC']/heapUsed | stats()"

Updating

# Update to latest version
jbang app install --force jfr-shell@btraceio

# Clear cache and reinstall
jbang cache clear
jbang app install jfr-shell@btraceio

Troubleshooting

JBang Not Found

Install JBang first (see Installation section above).

Java Version Mismatch

JBang automatically downloads Java 26+ if needed. Force a fresh install:

jbang --fresh jfr-shell@btraceio recording.jfr

Catalog Not Found

Add the catalog explicitly:

jbang catalog add --name btraceio https://raw.githubusercontent.com/btraceio/jbang-catalog/main/jbang-catalog.json
jbang catalog list  # Verify it's added

JitPack Build Issues

If using JitPack coordinates fails, check the build status at: https://jitpack.io/com/github/btraceio/jfr-shell/

You can trigger a fresh build by visiting that URL.

License

Apache License 2.0 - See the main repository for details.

Contributing

Issues and pull requests should be submitted to the main Jafar repository.