feat: Working goproxy implementation #55

js-murph · 2026-01-22T04:14:03Z

What?

This replaces the custom gomod handling and embeds https://github.com/goproxy/goproxy instead.

Why?

More robust and battle tested than our current implementation. It also should give us a path to supporting private modules as well via a custom fetcher in the future.

Tests

$ time curl http://localhost:8080/gomod/github.com/alecthomas/kong/@latest
{"Version":"v1.13.0","Time":"2025-11-12T21:31:44Z"}
real	0m0.976s
user	0m0.007s
sys	0m0.016s

$ time curl http://localhost:8080/gomod/github.com/alecthomas/kong/@latest
{"Version":"v1.13.0","Time":"2025-11-12T21:31:44Z"}
real	0m0.052s
user	0m0.006s
sys	0m0.012s

alecthomas · 2026-01-22T09:11:45Z

cachew.hcl

  max-ttl = "8h"
 }
+
+gomod {


alecthomas · 2026-01-22T09:12:12Z

internal/strategy/gomod.go

 	MutableTTL   time.Duration `hcl:"mutable-ttl,optional" help:"TTL for mutable Go module proxy endpoints (list, latest). Defaults to 5m." default:"5m"`
 	ImmutableTTL time.Duration `hcl:"immutable-ttl,optional" help:"TTL for immutable Go module proxy endpoints (versioned info, mod, zip). Defaults to 168h (7 days)." default:"168h"`


Are these relevant anymore?

alecthomas · 2026-01-22T09:13:30Z

internal/strategy/gomod_cacher.go

+// as a signal to fetch from upstream.
+func (g *goproxyCacher) Get(ctx context.Context, name string) (io.ReadCloser, error) {
+	// Hash the name to create a cache key that matches cachew's format
+	key := cache.Key(sha256.Sum256([]byte(name)))


Suggested change

key := cache.Key(sha256.Sum256([]byte(name)))

key := cache.NewKey(name)

alecthomas · 2026-01-22T09:14:27Z

internal/strategy/gomod_cacher.go

+	// Hash the name to create a cache key that matches cachew's format
+	key := cache.Key(sha256.Sum256([]byte(name)))
+
+	// Try to open the cached content


Can we get rid of all these completely superfluous comments? I find they make it quite a bit harder to comprehend what is actually going on.

I'm a bit surprised they're showing up TBH, the AGENTS.md file has explicit instructions about it 🤔

alecthomas · 2026-01-22T09:15:20Z

internal/strategy/gomod_cacher.go

+// it represents mutable or immutable content.
+func (g *goproxyCacher) Put(ctx context.Context, name string, content io.ReadSeeker) error {
+	// Hash the name to create a cache key
+	key := cache.Key(sha256.Sum256([]byte(name)))


Suggested change

key := cache.Key(sha256.Sum256([]byte(name)))

key := cache.NewKey(name)

alecthomas · 2026-01-22T09:20:16Z

internal/strategy/gomod_cacher.go

+// The TTL is determined by inspecting the cache name to identify whether
+// it represents mutable or immutable content.


Super weird, is this actually true? What is "name" in the context of the interface? Does it actually include things like /v@/list?

I checked and you are 100% right...that's super weird, as the default implementation doesn't seem to do any sort of timing out of /list entries etc...

Ah, I bet I know what's going on - I bet it uses an ETag to conditionally update it.

I think that means we can actually get rid of the two different TTL types, and just rely on the ETag to manage the cache.

I'm not at all convinced I'm correct about that actually, however it does seem to overwrite the list on every go get, as well as hit upstream list on every request...so there doesn't seem to be much point in having a TTL on list at all. If anything, it might be better to completely ignore /list...

DBG Request received client=127.0.0.1:56140 request="GET /gomod/github.com/alecthomas/chroma/@v/list" DBG Request received client=127.0.0.1:56142 request="GET /gomod/github.com/alecthomas/@v/list" DBG Request received client=127.0.0.1:56141 request="GET /gomod/github.com/@v/list" DBG Go module proxy outbound request method=GET url=https://proxy.golang.org/github.com/alecthomas/@v/list DBG Go module proxy outbound request method=GET url=https://proxy.golang.org/github.com/@v/list DBG Go module proxy outbound request method=GET url=https://proxy.golang.org/github.com/alecthomas/chroma/@v/list DBG goproxy.Get client=127.0.0.1:56141 request="GET /gomod/github.com/@v/list" name=github.com/@v/list DBG goproxy.Get client=127.0.0.1:56142 request="GET /gomod/github.com/alecthomas/@v/list" name=github.com/alecthomas/@v/list DBG goproxy.Put client=127.0.0.1:56140 request="GET /gomod/github.com/alecthomas/chroma/@v/list" name=github.com/alecthomas/chroma/@v/list DBG Request received client=127.0.0.1:56142 request="GET /gomod/github.com/dlclark/regexp2/@v/list" DBG Go module proxy outbound request method=GET url=https://proxy.golang.org/github.com/dlclark/regexp2/@v/list DBG goproxy.Put client=127.0.0.1:56142 request="GET /gomod/github.com/dlclark/regexp2/@v/list" name=github.com/dlclark/regexp2/@v/list

Super weird.

Also interestingly, on cold start it seems to hit the upstream no matter what. Subsequent runs are quite fast, so it appears it might have some in-memory caching too.

I'm not sure what to think about it all.

I checked the source and it does indeed just call the upstream. I also checked and the upstream has cache control headers with a 60 second TTL.

alecthomas · 2026-01-22T09:21:55Z

internal/strategy/gomod_cacher.go

+	ttl := g.calculateTTL(name)
+
+	// Determine Content-Type from the file extension
+	contentType := g.getContentType(name)


Does this make sense?

alecthomas · 2026-01-22T10:18:07Z

I pushed up a minor fix to configure it to use our logger, so it didn't spam to stdout, however it does spam errors for every package it pulls, for some reason:

Running:

~/dev/cachew $ GOPROXY=http://localhost:8080/gomod/ go get github.com/alecthomas/chroma@latest
go: added github.com/alecthomas/chroma v0.10.0

Gives:

ERR failed to list module versions error="not found: invalid github.com import path \"github.com\"" target=github.com/@v/list
ERR failed to list module versions error="not found: invalid github.com import path \"github.com/alecthomas\"" target=github.com/alecthomas/@v/list

I think we're going to need some kind of log interceptor to filter these out 😕

alecthomas · 2026-01-22T10:30:09Z

Okay fixed the logging too!

js-murph added 2 commits January 22, 2026 09:57

feat: Working goproxy implementation

1e09053

fix: A bold faced lie

497e629

js-murph requested a review from alecthomas as a code owner January 22, 2026 04:14

alecthomas reviewed Jan 22, 2026

View reviewed changes

fix: configure goproxy to use our logger

ff941e5

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feat: Working goproxy implementation #55

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js-murph commented Jan 22, 2026 •

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		MutableTTL time.Duration `hcl:"mutable-ttl,optional" help:"TTL for mutable Go module proxy endpoints (list, latest). Defaults to 5m." default:"5m"`
		ImmutableTTL time.Duration `hcl:"immutable-ttl,optional" help:"TTL for immutable Go module proxy endpoints (versioned info, mod, zip). Defaults to 168h (7 days)." default:"168h"`

	key := cache.Key(sha256.Sum256([]byte(name)))
	key := cache.NewKey(name)

		// The TTL is determined by inspecting the cache name to identify whether
		// it represents mutable or immutable content.

feat: Working goproxy implementation #55

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feat: Working goproxy implementation #55

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js-murph commented Jan 22, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Tests

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alecthomas Jan 22, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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alecthomas commented Jan 22, 2026

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js-murph commented Jan 22, 2026 •

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