Linux 平臺開源的跟蹤工具：LTTng
LTTng 是一個 Linux 平臺開源的跟蹤工具，是一套軟件組件，可允許跟蹤 Linux 內核和用戶程序，并控制跟蹤會話（開始/停止跟蹤、啟動/停止事件 等等）。這些組件被綁定如下三個包：
- LTTng-tools：庫和用于跟蹤會話的命令行接口
- LTTng-modules：允許用 LTTng 跟蹤 Linux 的 Linux 內核模塊
- LTTng-UST：用戶空間跟蹤庫 </ul>
- The Linux kernel, using either already available or user-defined instrumentation points
- C/C++ applications
- Java applications
- Any other user space application using the LTTng logger
- Trace locally: record a trace to the target's local filesystem, then use one of the many compatible viewers to investigate what happened.
- Trace remotely: send trace data over the network.
- View a live stream: monitor events as they occur, in real-time.
- Take a snapshot: when desired, keep only a fixed-sized log of the latest events.
LTTng is an open source tracing framework for Linux.
</div>System-wide insight
LTTng allows to understand the interactions between multiple components of a given system, i.e.:
Tracing all those components with LTTng will produce a unified log of events, providing great insight into the system's behavior. Here's a simplified example of a system trace:
...
17:23:05.035454 my-application startup
17:23:05.043948 my-application readConfigBegin
path: /home/mole/.my-app/config
17:23:05.044120 linux sys_open
pathname: /home/mole/.my-app/config
flags: O_RDONLY
ret: 5
17:23:05.044120 linux sys_fstat
fd: 5
ret:
st_uid: 1002
st_size: 4608
...
17:23:05.044498 linux sys_read
fd: 5
buf: 0x7fcd0128
count: 4608
17:23:05.046005 linux sys_close
fd: 5
17:23:05.047948 my-application readConfigEnd
17:23:06.164870 my-application getUser
username: joe
17:23:06.251164 java-db doQuery
query: SELECT * FROM users WHERE username = 'joe';
High performance
LTTng is designed from the ground up to provide low overhead tracing on production systems. This is achieved by using techniques such as per-CPU buffering, RCU data structures, a compact and efficient binary format (the Common Trace Format), etc.
LTTng disturbs the traced system as little as possible in order to make tracing of subtle race conditions and rare interrupt cascades possible.
On platforms where resources are limited, such as some Linux embedded systems, LTTng can be used out of the box to help developers pinpoint the sources of hard-to-debug issues.
LTTng offers a new approach to gain insight into your system's behavior.
Flexible
Whether your target is a small embedded system or a large cloud, LTTng provides flexible configuration options that can accommodate the system's workload. Architectures such as x86, PowerPC, ARM and MIPS are supported, amongst others.
LTTng's tracing session mechanism makes it possible to record multiple traces concurrently with different configuration options. Each user may create and configure as many tracing sessions as needed.
Depending on your specific scenario, you may wish to:
Easy
As LTTng is packaged for all major Linux distributions, installing it is done through package managers.
A single tool, the lttng command line interface, is used to control the whole framework.
Multiple ways to view and analyze the traces produced by LTTng exist: GUI, CLI tools, and custom scripts.