super basic wasm filter implementation using wazero

[szuecs]

A very simple implementation to test how WASM support #2946 could look like.

wasm code compile with tinygo, but it could also be some other compiler:

% tinygo build -o add.wasm -target=wasi add.go

export request (add(x,y)) and response (sub(x,y))

% cat /home/sszuecs/go/src/github.com/zalando/skipper/filters/wasm/testdata/add.go
package main

//export request
func request(x, y uint32) uint32 {
        return x + y
}

//export response
func response(x, y uint32) uint32 {
        return x - y
}

// main is required for the `wasi` target, even if it isn't used.
// See https://wazero.io/languages/tinygo/#why-do-i-have-to-define-main
func main() {}

% ./bin/skipper -inline-routes='r: * -> status(200) -> wasm("file:///home/sszuecs/go/src/github.com/zalando/skipper/filters/wasm/testdata/add.wasm") -> <shunt>'
[APP]INFO[0000] Expose metrics in codahale format
[APP]INFO[0000] enable swarm: false
[APP]INFO[0000] Replacing tee filter specification
[APP]INFO[0000] Replacing teenf filter specification
[APP]INFO[0000] Replacing lua filter specification
[APP]INFO[0000] support listener on :9911
[APP]INFO[0000] Dataclients are updated once, first load complete
[APP]INFO[0000] Listen on :9090
[APP]INFO[0000] route settings, reset, route: r: * -> status(200) -> wasm("file:///home/sszuecs/go/src/github.com/zalando/skipper/filters/wasm/testdata/add.wasm") -> <shunt>
[APP]INFO[0000] route settings received
[APP]INFO[0000] TLS settings not found, defaulting to HTTP
[APP]INFO[0000] route settings applied
[APP]INFO[0012] request result: [5]     <- request(2,3) result
[APP]INFO[0012] response result: [1]    <- response(3,2) result
::1 - - [19/Feb/2024:17:35:54 +0100] "GET /foo HTTP/1.1" 200 0 "-" "curl/7.49.0" 0 localhost:9090 - -

Load error would look like:

[APP]INFO[0000] route settings, reset, route: r: * -> status(200) -> wasm("file://filters/wasm/testdata/add.wasm") -> <shunt>
[APP]INFO[0000] route settings received
[APP]ERRO[0000] Failed to load file "/wasm/testdata/add.wasm": open /wasm/testdata/add.wasm: no such file or directory
[APP]ERRO[0000] failed to process route r: failed to create filter "wasm": invalid filter parameters
[APP]INFO[0000] route settings applied

[AlexanderYastrebov]

I think we should make this lazy and cacheable and cleanup on filter close

[szuecs]

yes, as I wrote in the PR title super basic. I used https://github.com/tetratelabs/wazero/tree/main/examples/basic to test the super basic example.