A tool analyzes tcp packets with Lua
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README.md

tcpkit

A tool to capture tcp packets and analyze the packets with LUA.

Usage

TCPKIT is a tool to capture tcp packets and analyze the packets with lua.
	-s which server ip to monitor, must specify when runing in client side. e.g. 192.168.1.2,192.168.1.3 
	-p which n_latency to monitor, e.g. 6379,6380
	-P stats listen port, default is 33333
	-i network card interface, e.g. bond0, lo, em0... see 'ifconfig'
	-d daemonize, run process in background
	-r set offline file captured by tcpdump or tcpkit
	-t request latency threshold, unit is millisecond
	-m protocol mode, raw,redis,memcached,http
	-w dump packets to 'savefile'
	-S lua script path, default is ../scripts/example.lua
	-B operating system capture buffer size, in units of KiB (1024 bytes)
	-o log output file
	-u udp
	-v version
	-h help

Install

$ git clone https://github.com/git-hulk/tcpkit.git tcpkit
$ cd tcpkit
$ sudo make && make install

Monitor latency

Supports Redis/Memcached/Http protocol now, we take Redis as example here:

$ sudo tcpkit -i em1 -s 192.168.1.2 -p 6379,6380,6381 -t 10 -m redis

and the request latency more than 10ms would be printed, like below:

2018-11-16 18:38:36.873067 172.20.64.106:53499 => 192.168.1.2:6379 | 11 ms | set foo bar
2018-11-16 18:38:55.051167 172.20.64.106:53499 => 192.168.1.2:6379 | 14 ms | get foo

Tcpkit would print all requests if the -t option wasn't set. If tcpkit was deployed client-side, use the -s option to specify the server host/ip.

Caution: -s option should be specified when tcpkit is running in client side or decode packets from offline pcap.

Use lua to analyze packets

If the protocol wasn't supported by tcpkit or to inspect the tcp stream data, we can use raw mode. The tcp packet would be passed to lua VM, and we can analyze the packet with lua script. e.g.

$ sudo tcpkit -i em1 -p 6379 -m raw -S ../scripts/example.lua 

Scripts

  1. exmaple.lua - example for user defined script
  2. dns.lua - print the dns latency
  3. tcp-connnect.lua - print connection with syn packet retransmit

Fetch Stats Online

Tcpkit also exports latency stats to the user by tcp port (default is 33333), use the -P option to change it. The output is a json string, like below:

[{"6379":{"total_reqs": 7,"total_costs":76785, "slow_reqs":7,"latencies":[0,0,0,0,0,3,3,1,0,0,0,0,0,0,0,0,0,0]}},
{"6380":{"total_reqs": 0,"total_costs":0, "slow_reqs":0,"latencies":[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]}}]

This means that the port 6379 received 7 total requests, and that total costs is 76785 us, with 7 slow requests (slow threshold is 5ms): 5ms-10ms: 3 requests 10ms-20ms: 3 requests 20ms-50ms: 1 request

The latencies arrays above correspond to the following latency buckets: 0.1ms, 0.2ms, 0.5ms, 1ms, 5ms, 10ms, 20ms, 50ms, 100ms, 200ms, 500ms, 1s, 2s, 3s, 5s, 10s, 20s, >20s