Analyzer lj-lua-off-cpu

# Name

lj-lua-off-cpu - Lua-Land off-CPU Flame Graph

This analyzer profiles off-CPU time in Lua-land code execution within LuaJIT-based applications such as OpenResty and Kong. It captures stack traces when Lua code is blocked or waiting, such as during I/O operations, lock contention, or sleep calls. The analyzer generates flame graphs that visualize time spent in blocking operations across Lua-level function calls, helping identify performance bottlenecks caused by waiting rather than active CPU usage. This is particularly useful for diagnosing latency issues in web applications and API gateways.

# Resource Category

off-CPU.

# Application Type & Technical Stack

• OpenResty
• Kong
• APISIX

# Command Line Syntax

The analyzer can be invoked directly on the command-line via the orxray utility from the openresty-xray-cli software package.

Alternatively, the analyzer can also be invoked manually or automatically on the web console UI of OpenResty XRay (like on the Advanced web page).

# PID is the target process PID.
orxray analyzer run lj-lua-off-cpu -p PID

# trace a shell command directly
orxray analyzer run lj-lua-off-cpu -c SHELL_CMD

# PGID is the process group ID or any process's PID within the target process
# group.
orxray analyzer run lj-lua-off-cpu -p -PGID

# trace any processes started from the specified executable path.
orxray analyzer run lj-lua-off-cpu --exe /path/to/exe/file

# Tracing Multiple Processes

Supported.

# Output Formats

• Flame Graphs

# Author

The OpenResty Inc. Team.

# Copyright

Copyright (C) by OpenResty Inc. All rights reserved.