introduce zstd for compression by gipeshka · Pull Request #4185 · zio/zio-http

gipeshka · 2026-06-24T14:52:21Z

Addressing #4184.

Not including zstd jni, to use this I assume one would have to manually enable it (just like one has to do it now for zio-http to start accepting zstd content-encoding)

CLAassistant · 2026-06-24T14:52:39Z

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Pull request overview

Adds server-side zstd response compression support (Accept-Encoding negotiation via Netty HttpContentCompressor), aligning with the existing ability to accept Content-Encoding: zstd when users provide the JNI dependency.

Changes:

Introduces CompressionOptions.Zstd plus ZstdConfig and a CompressionOptions.zstd(...) constructor.
Extends CompressionOptions.config parsing to recognize "type" = "zstd" and read zstd-specific parameters.
Adds Netty conversion support for zstd via StandardCompressionOptions.zstd(...).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
`zio-http/shared/src/main/scala/zio/http/Server.scala`	Adds zstd compression option/config and updates config parsing to support selecting zstd.
`zio-http/jvm/src/main/scala/zio/http/netty/model/Conversions.scala`	Maps the new zstd compression option into Netty `StandardCompressionOptions.zstd(...)`.

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987Nabil · 2026-06-26T06:29:22Z

@gipeshka Please fix the build. Rebase might just do it

gipeshka · 2026-07-01T16:46:44Z

@987Nabil thanks for letting me know, it's fixed now

987Nabil

Found a functional bug in the zstd defaults — see inline comment. The blockSize/maxEncodeSize defaults are swapped relative to Netty's actual ZstdConstants. With the current values, CompressionOptions.zstd() (no args) sets maxEncodeSize = 65536, so any response body that compresses to more than 64 KB will throw (maxEncodeSize bounds the largest compressible object), while blockSize = Integer.MAX_VALUE is backwards too. Everything else (Conversions.scala mapping, param order into StandardCompressionOptions.zstd(level, blockSize, maxEncodeSize), config parsing wiring, CI/Mima) checks out — this is the one blocking issue.

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Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

987Nabil · 2026-07-25T18:41:06Z

          typ.toLowerCase match {
            case "gzip"    => gzip(level, bits, mem)
            case "deflate" => deflate(level, bits, mem)
            case "brotli"  => brotli(quantity, lgwin, mode)
+            case "zstd"    => zstd(level, block, maxencode)


@gipeshka this seems to be a legit concern

makes sense. @987Nabil what would be the preferred way of solving it? Would isolating level for zstd under a dedicated config prefix like zstdlevel work?

@987Nabil I've adjusted it via optional. Please have a look

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Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

Suppressed comments (3)

zio-http/shared/src/main/scala/zio/http/Server.scala:422

All sibling public compression factories document that their defaults correspond to Netty's default option object, but the newly added zstd factory omits that API documentation. Document the same default relationship here so callers can understand the three otherwise non-obvious tuning parameters.

      def zstd(

zio-http/shared/src/main/scala/zio/http/Server.scala:321

The new supported encoding is not represented by the typed header API. Header.AcceptEncoding still exposes zstd only as Unknown, and Header.ContentEncoding.parse drops zstd, so a response compressed by this option cannot be observed through response.header(Header.ContentEncoding). Add Zstd variants to both header algebras, update their parsers/rendering, and cover them in HeaderSpec.

      final case class Zstd(cfg: ZstdConfig)       extends CompressionOptions { val name = "zstd"    }

zio-http/jvm/src/main/scala/zio/http/netty/model/Conversions.scala:174

This new conversion branch has no end-to-end coverage, although ResponseCompressionSpec verifies the existing response codecs. Add a test-scoped zstd-jni dependency and an integration test that enables only this option, requests Accept-Encoding: zstd, verifies Content-Encoding: zstd, and decompresses the body; a test-scoped dependency would not impose JNI on library consumers.

      case CompressionOptions.Zstd(cfg)    =>
        StandardCompressionOptions.zstd(cfg.level, cfg.blockSize, cfg.maxEncodeSize)

Copilot

🟡 Changes recommended

The Zstandard path lacks integration coverage, and its configuration keys need normalization.

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Review details

Files reviewed: 2/2 changed files
Comments generated: 2
Review effort level: Balanced

Copilot

🔵 Needs a closer look

Unknown compression types still cause an untyped MatchError during configuration loading.

Review details

Suppressed comments (1)

zio-http/shared/src/main/scala/zio/http/Server.scala:471

The algorithm-specific level defaults are fixed, but an unsupported type still falls through this partial match and throws MatchError while loading configuration. Parse with mapOrFail and return InvalidData for unknown values so configuration failures stay typed and actionable.

            case "zstd"    => zstd(level.getOrElse(ZstdConfig.DefaultLevel), block, maxencode)

Files reviewed: 2/2 changed files
Comments generated: 0 new
Review effort level: Balanced

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987Nabil · 2026-09-09T09:21:24Z

      case CompressionOptions.Brotli(cfg)  =>
        StandardCompressionOptions.brotli(cfg.quality, cfg.lgwin, brotliModeToJava(cfg.mode))
+      case CompressionOptions.Zstd(cfg)    =>
+        StandardCompressionOptions.zstd(cfg.level, cfg.blockSize, cfg.maxEncodeSize)


Please add an end-to-end test for this new path. A test-scoped zstd-jni dependency can configure only CompressionOptions.zstd(), request Accept-Encoding: zstd, assert the response encoding, and decompress the body. Including a response larger than 64 KiB would also protect the corrected blockSize/maxEncodeSize defaults.

987Nabil · 2026-09-09T09:21:24Z

@@ -344,6 +344,7 @@ object Server extends ServerPlatformSpecific {
      final case class GZip(cfg: DeflateConfig)    extends CompressionOptions { val name = "gzip"    }


Adding Zstd here makes it a supported response content coding, but the typed header API is not updated: Header.ContentEncoding.parse("zstd") currently fails, and AcceptEncoding can represent it only as Unknown. Please add typed Zstd variants to both header algebras, update parsing/rendering, and cover them in HeaderSpec.

987Nabil · 2026-09-09T09:21:24Z

@@ -432,20 +445,30 @@ object Server extends ServerPlatformSpecific {
      ): CompressionOptions =


Could this public factory get Scaladoc like the gzip/deflate/brotli factories above? In particular, document the Netty defaults and that callers must provide the optional zstd-jni runtime dependency; otherwise selecting this option fails during Netty option construction.

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Comment thread zio-http/shared/src/main/scala/zio/http/Server.scala

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gipeshka force-pushed the introduce-zstd-for-compression branch from 348ecb6 to dfcbdf6 Compare July 1, 2026 16:21

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gipeshka force-pushed the introduce-zstd-for-compression branch from 19bf52c to 31d500d Compare July 6, 2026 09:08

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gipeshka force-pushed the introduce-zstd-for-compression branch from 141aaa5 to fdbbd4c Compare September 4, 2026 14:43

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Comment thread zio-http/jvm/src/main/scala/zio/http/netty/model/Conversions.scala

Comment thread zio-http/shared/src/main/scala/zio/http/Server.scala Outdated

gipeshka requested a balanced review from Copilot September 8, 2026 09:38

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introduce zstd for compression

6b51e0a

gipeshka and others added 4 commits September 9, 2026 11:12

Potential fix for pull request finding

23edd4a

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

invert block size and max encode

b2e50cd

added fix default level

2aeec47

adjust config keys

bcbb9d4

gipeshka force-pushed the introduce-zstd-for-compression branch from 8d6267e to bcbb9d4 Compare September 9, 2026 09:12

987Nabil reviewed Sep 9, 2026

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		@@ -344,6 +344,7 @@ object Server extends ServerPlatformSpecific {
		final case class GZip(cfg: DeflateConfig) extends CompressionOptions { val name = "gzip" }

		@@ -432,20 +445,30 @@ object Server extends ServerPlatformSpecific {
		): CompressionOptions =

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