Anis Elleuch 98d3f94996
metrics: Add the number of requests in the waiting queue (#11580)
We can use this metric to check if there are too many S3 clients in the
queue and could explain why some of those S3 clients are timing out.

```
minio_s3_requests_waiting_total{server="127.0.0.1:9000"} 9981
```

If max_requests is 10000 then there is a strong possibility that clients
are timing out because of the queue deadline.
2021-02-20 00:21:55 -08:00
..
2021-01-26 20:47:42 -08:00
2020-01-31 08:29:22 +05:30