At Lyft we have a plethora of tools for monitoring Envoy that take advantage of the logging and stats output, which are aggregated for every host into a central cluster. Sometimes you just want to see what's happening on a box right now though. I hacked together a couple of command line tools for monitoring envoy in real-time. curl and grep against the admin endpoints in combination with watch is pretty useful at times so I decided to make a dedicated tool. The other benefit of the tool is that it can diff the gauge values to give you number per interval for stats like cluster.foo.upstream_rq_2xx.

Here's example output from my tool, similar to iostat, mpstat, vmstat, etc.

$ envoystat -p http.router.downstream 1
2018/01/16 envoy 8cf90bcb/1.6.0-dev/Modified/RELEASE live 354839 354839 0

08:12:44 PM cx_active' rq_active'     rq_2xx     rq_4xx     rq_5xx   rq_total
08:12:44 PM        420         40        266          2          0        315
08:12:45 PM        420         29        305          1          0        313
08:12:46 PM        421         35        274          3          0        314
08:12:47 PM        420         27        226          2          0        244
08:12:48 PM        421         21        221          2          0        241
08:12:49 PM        420         29        246          2          0        276
08:12:50 PM        420         35        284          4          0        314
08:12:51 PM        420         29        276          2          0        290
08:12:52 PM        420         28        242          7          0        275
08:12:53 PM        421         24        221          2          0        240
^C

I wrote it in Python about 30 minutes and it wouldn't take much to make it more generic and broadly useful for various deployments of Envoy. Also planning to have a mode that analyzes the local access log and outputs top values for various fields (user agent, IP, etc).

@mccv has also been working on some cli tools. Looking for some details from him and any other opinions before building mine out more.