Analyzer lj-write-latency-fgraph

# Name

lj-write-latency-fgraph - Lua-Land Virtual File System Write Latency Flame Graph

This analyzer profiles latency of file system write operations in Lua-land code within LuaJIT-based applications such as OpenResty and Kong. It captures stack traces during virtual file system write 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 write operations and troubleshoot disk I/O performance issues.

# 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-write-latency-fgraph -p PID

# trace a shell command directly
orxray analyzer run lj-write-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-write-latency-fgraph -p -PGID

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