add StatsService.GetSysStats

[vcptr]

1. add StatsService.GetSysStats call to v2ctl to retrieve core running data, example:

$ /usr/bin/v2ray/v2ctl api --server=127.0.0.1:10085 StatsService.GetSysStats ''
NumGoroutine: 16
NumGC: 5
Alloc: 717048
TotalAlloc: 5185696
Sys: 71762168
Mallocs: 55768
Frees: 48457
LiveObjects: 7311
PauseTotalNs: 706772
Uptime: 589

2. fixed bug running command v2ctl api without arguments, hangs forever with no output/error.

[xiaokangwang]

I think this pull request is ready to be merged.

[xiaokangwang]

This pull request have added a 3 second timeout to grpc request in v2ctl. I believe this behavior should be reflected in document to prevent confusion in the future.

[vcptr]

Actually the previous behavior is more confusing, grpc dial have a infinite timeout, the command just hangs forever.

[xiaokangwang]

Yes, however, we can't assume all commands can be completed in 3 seconds.

[vcptr]

I think we can.

Any cli command does not response in a human bearable time and tells what happened, is bad design.

A three seconds waiting is suitable in this situation.

[xiaokangwang]

Currently, this is the case, but I think this change should be documented nonetheless.

[vcptr]

a notice line added, heres the help text:

$ ./v2ctl api --help
Usage of api:
  -server string
        Server address (default "127.0.0.1:8080")
v2ctl api [--server=127.0.0.1:8080] Service.Method Request
Call an API in an V2Ray process.
The following methods are currently supported:
        LoggerService.RestartLogger
        StatsService.GetStats
        StatsService.QueryStats
API calls in this command have a timeout to the server of 3 seconds.
Examples:
v2ctl api --server=127.0.0.1:8080 LoggerService.RestartLogger '' 
v2ctl api --server=127.0.0.1:8080 StatsService.QueryStats 'pattern: "" reset: false'
v2ctl api --server=127.0.0.1:8080 StatsService.GetStats 'name: "inbound>>>statin>>>traffic>>>downlink" reset: false'
v2ctl api --server=127.0.0.1:8080 StatsService.GetSysStats ''

[xiaokangwang]

I believe this pull request is ready to be merged.