JSON Push API endpoint broken

[lukesteensen]

Describe the bug
The push API endpoint no longer accepts JSON data, returning a 400 and snappy: corrupt input.

To Reproduce
Steps to reproduce the behavior:

1. Started Loki (docker run --rm -it --network=host grafana/loki:master-51952da)
2. Send the example curl request from the API docs.

Expected behavior
The request should succeed.

Environment:

• Infrastructure: local Ubuntu machine
• Deployment tool: docker

Screenshots, Promtail config, or terminal output

$ curl -v -H "Content-Type: application/json" -XPOST -s "http://localhost:3100/loki/api/v1/push" --data-raw '{"streams": [{ "stream": { "foo": "bar2" }, "values": [ [ "1570818238000000000", "fizzbuzz" ] ] }]}'
*   Trying 127.0.0.1:3100...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 3100 (#0)
> POST /loki/api/v1/push HTTP/1.1
> Host: localhost:3100
> User-Agent: curl/7.68.0
> Accept: */*
> Content-Type: application/json
> Content-Length: 99
> 
* upload completely sent off: 99 out of 99 bytes
* Mark bundle as not supporting multiuse
< HTTP/1.1 400 Bad Request
< Content-Type: text/plain; charset=utf-8
< X-Content-Type-Options: nosniff
< Date: Thu, 28 Jan 2021 21:22:58 GMT
< Content-Length: 22
< 
snappy: corrupt input

[dannykopping]

Hey @lukesteensen - thanks for reporting.
We noticed it to and have pushed a fix already (#3261)

[lukesteensen]

Great, thank you!