Added support for snappy to enable prometheus remote write (#8983)

Adding a feature.

This adds `snappy` support for the confighttp compression package.
This provides support for enabling the prometheus remote write receiver
which only supports snappy.

#7632

Added unit test coverage and testing integration with prometheus remote
write compatibility.

---------

Co-authored-by: Bogdan Drutu <bogdandrutu@gmail.com>

.chloggen/add-snappy-confighttp-decompress.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: confighttp
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Adds support for Snappy decompression of HTTP requests.
+
+# One or more tracking issues or pull requests related to the change
+issues: [7632]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

config/confighttp/compression.go

@@ -13,6 +13,7 @@ import (
 	"io"
 	"net/http"
 
+	"github.com/golang/snappy"
 	"github.com/klauspost/compress/zstd"
 
 	"go.opentelemetry.io/collector/config/configcompression"
@@ -117,6 +118,18 @@ func httpContentDecompressor(h http.Handler, eh func(w http.ResponseWriter, r *h
 				}
 				return zr, nil
 			},
+			"snappy": func(body io.ReadCloser) (io.ReadCloser, error) {
+				sr := snappy.NewReader(body)
+				sb := new(bytes.Buffer)
+				_, err := io.Copy(sb, sr)
+				if err != nil {
+					return nil, err
+				}
+				if err = body.Close(); err != nil {
+					return nil, err
+				}
+				return io.NopCloser(sb), nil
+			},
 		},
 	}
 	d.decoders["deflate"] = d.decoders["zlib"]

config/confighttp/compression_test.go

@@ -190,6 +190,12 @@ func TestHTTPContentDecompressionHandler(t *testing.T) {
 			reqBody:  compressZstd(t, testBody),
 			respCode: http.StatusOK,
 		},
+		{
+			name:     "ValidSnappy",
+			encoding: "snappy",
+			reqBody:  compressSnappy(t, testBody),
+			respCode: http.StatusOK,
+		},
 		{
 			name:     "InvalidDeflate",
 			encoding: "deflate",
@@ -218,6 +224,13 @@ func TestHTTPContentDecompressionHandler(t *testing.T) {
 			respCode: http.StatusBadRequest,
 			respBody: "invalid input: magic number mismatch",
 		},
+		{
+			name:     "InvalidSnappy",
+			encoding: "snappy",
+			reqBody:  bytes.NewBuffer(testBody),
+			respCode: http.StatusBadRequest,
+			respBody: "snappy: corrupt input\n",
+		},
 		{
 			name:     "UnsupportedCompression",
 			encoding: "nosuchcompression",