Analyzer lj-read-latency-fgraph

# Name

lj-read-latency-fgraph - Lua-Land Virtual File System Read/Sendfile Latency Flame Graph

This analyzer profiles latency of file system read and sendfile operations in Lua-land code within LuaJIT-based applications such as OpenResty and Kong. It captures stack traces during virtual file system read/sendfile calls and measures their execution time in microseconds. The analyzer generates flame graphs that visualize latency distribution across Lua-level function calls, helping identify slow file I/O operations and optimize disk access patterns in web applications.

# Resource Category

Disk I/O.

# 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-read-latency-fgraph -p PID

# trace a shell command directly
orxray analyzer run lj-read-latency-fgraph -c SHELL_CMD

# PGID is the process group ID or any process's PID within the target process
# group.
orxray analyzer run lj-read-latency-fgraph -p -PGID

# trace any processes started from the specified executable path.
orxray analyzer run lj-read-latency-fgraph --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.