prometheus federate no data

[criss...@gmail.com]

hi all.

I wonder if someone could help me with the following issue, 

I open prometheus sidecar function and  thanos .  But my federated interface data is empty.

My old business interface needs federate.

# curl -i 172.28.12.78:9090/federate

HTTP/1.1 200 OK

Content-Type: text/plain; version=0.0.4; charset=utf-8

Date: Mon, 27 Sep 2021 09:41:19 GMT

Content-Length: 0

my config

```

1. prometheus    

Containers:

  prometheus:

    Image:         prometheus:v2.28.1

    Args:

      --web.console.templates=/etc/prometheus/consoles

      --web.console.libraries=/etc/prometheus/console_libraries

      --config.file=/etc/prometheus/config_out/prometheus.env.yaml

      --storage.tsdb.path=/prometheus

      --storage.tsdb.retention.time=4h

      --query.timeout=60s

      --web.external-url=http://prometheus.xxx.com/

      --web.route-prefix=/

      --web.config.file=/etc/prometheus/web_config/web-config.yaml

      --storage.tsdb.max-block-duration=2h

      --storage.tsdb.min-block-duration=2h

```

[Brian Candler]

Yes, I get the same if I send an empty federate query.  You need to include a match[] part, e.g.

curl -ig 'prometheus:9090/federate?match[]={__name__=~".%2b"}'