Loki: Change how push API checks for contentType (#4443)

* Change how push API checks for contentType

- Currently, the ContentType is expected to be exactly
  "application/json". That's a problem because although a
"application/json; charset=utf-8" is considered a valid JSON content
type, it will be seen as an error.

* Use mime.ParseMediaType to parse contentType.

- mime.ParseMediaType is more reliable than strings.Contains because if
  a wrong contentType (such as "application/jsonnn") is given, we still
accept it
- mime.ParseMediaType has support for contentType parameters. This way,
  valid contentTypes such as "application/json; charset=utf-8" will not
be rejected

* Add changelog entry.

* Change body in test to avoid lint issues.

- Without this change, the lint fails because gzipString would be called
  with always the same input. Full error:
```
`gzipString` - `source` always receives ``{"streams": [{ "stream": {
"foo": "bar2" }, "values": [ [ "1570818238000000000", "fizzbuzz" ] ]
}]}` ("{\"streams\": [{ \"stream\": { \"foo\": \"bar2\" }, \"values\": [
[ ...)
` (unparam)
```

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## Main
 * [4400](https://github.com/grafana/loki/pull/4400) **trevorwhitney**: Config: automatically apply memberlist config too all rings when provided
+* [4443](https://github.com/grafana/loki/pull/4443) **DylanGuedes**: Loki: Change how push API checks for contentType
 
 # 2.3.0 (2021/08/06)
 

pkg/loghttp/push/push.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"math"
+	"mime"
 	"net/http"
 	"time"
 
@@ -78,8 +79,14 @@ func ParseRequest(logger log.Logger, userID string, r *http.Request, tenantsRete
 		req              logproto.PushRequest
 	)
 
+	contentType, _ /* params */, err := mime.ParseMediaType(contentType)
+	if err != nil {
+		return nil, err
+	}
+
 	switch contentType {
 	case applicationJSON:
+
 		var err error
 
 		// todo once https://github.com/weaveworks/common/commit/73225442af7da93ec8f6a6e2f7c8aafaee3f8840 is in Loki.

pkg/loghttp/push/push_test.go

@@ -72,6 +72,27 @@ func TestParseRequest(t *testing.T) {
 			contentEncoding: `snappy`,
 			valid:           false,
 		},
+		{
+			path:            `/loki/api/v1/push`,
+			body:            gzipString(`{"streams": [{ "stream": { "foo": "bar2" }, "values": [ [ "1570818238000000000", "fizzbuzz" ] ] }]}`),
+			contentType:     `application/json; charset=utf-8`,
+			contentEncoding: `gzip`,
+			valid:           true,
+		},
+		{
+			path:            `/loki/api/v1/push`,
+			body:            gzipString(`{"streams": [{ "stream": { "foo": "bar2" }, "values": [ [ "1570818238000000000", "fizzbuzz" ] ] }]}`),
+			contentType:     `application/jsonn; charset=utf-8`,
+			contentEncoding: `gzip`,
+			valid:           false,
+		},
+		{
+			path:            `/loki/api/v1/push`,
+			body:            gzipString(`{"streams": [{ "stream": { "foo4": "bar2" }, "values": [ [ "1570818238000000000", "fizzbuzz" ] ] }]}`),
+			contentType:     `application/json; charsetutf-8`,
+			contentEncoding: `gzip`,
+			valid:           false,
+		},
 	}
 
 	// Testing input array