compression: fix nocgo build

Also add `make testnocgo` target and update the nightly workflow
(note: we were running this without invariants before, that was not
intentional). We also add this build to the CI builds that run on each
PR.

Author: RaduBerinde

.github/workflows/ci.yaml

@@ -63,6 +63,19 @@ jobs:
 
       - run: GOTRACEBACK=all make test TAGS=
 
+  linux-no-cgo:
+    name: go-linux-no-cgo
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: '1.24'
+
+      - run: GOTRACEBACK=all make testnocgo
+
   linux-race:
     name: linux-race
     runs-on: ubuntu-latest

.github/workflows/tests.yaml

@@ -171,7 +171,7 @@ jobs:
         with:
           go-version: ${{ inputs.go_version }}
 
-      - run: GOTRACEBACK=all CGO_ENABLED=0 make test TAGS=
+      - run: GOTRACEBACK=all make testnocgo
 
       - name: Post issue on failure
         if: failure() && inputs.file_issue_branch != ''

Makefile

@@ -44,6 +44,10 @@ testmsan: testflags += -msan -timeout 20m
 testmsan: TAGS += slowbuild
 testmsan: test
 
+.PHONY: testnocgo
+testnocgo:
+	CGO_ENABLED=0 ${GO} test -tags '$(TAGS)' ${testflags} -run ${TESTS} ${PKG}
+
 .PHONY: testobjiotracing
 testobjiotracing:
 	${GO} test -tags '$(TAGS) pebble_obj_io_tracing' ${testflags} -run ${TESTS} ./objstorage/objstorageprovider/objiotracing

internal/compression/zstd_nocgo.go

@@ -8,19 +8,22 @@ package compression
 
 import (
 	"encoding/binary"
+	"sync"
 
 	"github.com/cockroachdb/errors"
 	"github.com/cockroachdb/pebble/internal/base"
 	"github.com/klauspost/compress/zstd"
 )
 
-type zstdCompressor zstd.Encoder
+type zstdCompressor struct {
+	level   int
+	encoder *zstd.Encoder
+}
 
 var _ Compressor = (*zstdCompressor)(nil)
 
-func getZstdCompressor(level int) *zstdCompressor {
-	writer, _ := zstd.NewWriter(nil, zstd.WithEncoderLevel(zstd.EncoderLevelFromZstd(level)))
-	return (*zstdCompressor)(writer)
+var zstdCompressorPool = sync.Pool{
+	New: func() any { return &zstdCompressor{} },
 }
 
 // UseStandardZstdLib indicates whether the zstd implementation is a port of the
@@ -39,14 +42,27 @@ func (z *zstdCompressor) Compress(compressedBuf, b []byte) ([]byte, Setting) {
 		compressedBuf = append(compressedBuf, make([]byte, binary.MaxVarintLen64-len(compressedBuf))...)
 	}
 	varIntLen := binary.PutUvarint(compressedBuf, uint64(len(b)))
-	res := (*zstd.Encoder)(z).EncodeAll(b, compressedBuf[:varIntLen])
+	res := z.encoder.EncodeAll(b, compressedBuf[:varIntLen])
 	return res, Setting{Algorithm: Zstd, Level: uint8(z.level)}
 }
 
 func (z *zstdCompressor) Close() {
-	if err := (*zstd.Encoder)(z).Close(); err != nil {
+	if err := z.encoder.Close(); err != nil {
+		panic(err)
+	}
+	z.encoder = nil
+	zstdCompressorPool.Put(z)
+}
+
+func getZstdCompressor(level int) *zstdCompressor {
+	encoder, err := zstd.NewWriter(nil, zstd.WithEncoderLevel(zstd.EncoderLevelFromZstd(level)))
+	if err != nil {
 		panic(err)
 	}
+	z := zstdCompressorPool.Get().(*zstdCompressor)
+	z.level = level
+	z.encoder = encoder
+	return z
 }
 
 type zstdDecompressor struct{}