Merge pull request #36 from aki-0421/fetch-event

Full support for FetchEvent

README.md

@@ -28,10 +28,7 @@
   - [x] Calling stubs
 * [x] D1 (alpha)
 * [x] Environment variables
-* FetchEvent's [lifecycle methods](https://developers.cloudflare.com/workers/runtime-apis/fetch-event/#lifecycle-methods)
-  - [x] waitUntil
-  - [ ] respondWith
-  - [ ] passThroughOnException
+* [x] FetchEvent
 
 ## Installation
 

cloudflare/fetchevent.go

@@ -12,9 +12,8 @@ import (
 // It accepts an asynchronous task which the Workers runtime will execute before the handler terminates but without blocking the response.
 // see: https://developers.cloudflare.com/workers/runtime-apis/fetch-event/#waituntil
 func WaitUntil(ctx context.Context, task func()) {
-	executionContext := cfruntimecontext.GetExecutionContext(ctx)
-
-	executionContext.Call("waitUntil", jsutil.NewPromise(js.FuncOf(func(this js.Value, pArgs []js.Value) any {
+	exCtx := cfruntimecontext.GetExecutionContext(ctx)
+	exCtx.Call("waitUntil", jsutil.NewPromise(js.FuncOf(func(this js.Value, pArgs []js.Value) any {
 		resolve := pArgs[0]
 		go func() {
 			task()
@@ -23,3 +22,18 @@ func WaitUntil(ctx context.Context, task func()) {
 		return js.Undefined()
 	})))
 }
+
+// PassThroughOnException prevents a runtime error response when the Worker script throws an unhandled exception.
+// Instead, the request forwards to the origin server as if it had not gone through the worker.
+// see: https://developers.cloudflare.com/workers/runtime-apis/fetch-event/#passthroughonexception
+func PassThroughOnException(ctx context.Context) {
+	exCtx := cfruntimecontext.GetExecutionContext(ctx)
+	jsutil.AwaitPromise(jsutil.NewPromise(js.FuncOf(func(this js.Value, pArgs []js.Value) any {
+		resolve := pArgs[0]
+		go func() {
+			exCtx.Call("passThroughOnException")
+			resolve.Invoke(js.Undefined())
+		}()
+		return js.Undefined()
+	})))
+}

examples/fetch-event/Makefile

@@ -0,0 +1,13 @@
+.PHONY: dev
+dev:
+	wrangler dev
+
+.PHONY: build
+build:
+	mkdir -p dist
+	#tinygo build -o ./dist/app.wasm -target wasm ./...
+	tinygo build -o ./dist/app.wasm -target wasm -no-debug ./...
+
+.PHONY: publish
+publish:
+	wrangler publish

examples/fetch-event/README.md

@@ -0,0 +1,48 @@
+# [FetchEvent](https://developers.cloudflare.com/workers/runtime-apis/fetch-event/)
+
+Normally, workers are designed to return some kind of HTTP Response and exit immediately upon receiving an HTTP request. `FetchEvent` can extend these life cycles.
+
+#### WaitUntil
+
+`WaitUntil` extends the lifetime of the "fetch" event. It accepts an asynchronous task which the Workers runtime will execute without blocking the response. The worker will not be terminated until those tasks are completed.
+
+#### PassThroughOnException
+
+`PassThroughOnException` prevents a runtime error response when the Worker script throws an unhandled exception. Instead, the request forwards to the origin server as if it had not gone through the worker.
+
+## Example
+
+### Usecase
+
+You have decided to implement a log stream API to capture all access logs. You must edit the Headers so that the user's API token is not logged. If an unknown error occurs during this process, the entire service will be down, which must be avoided.
+In such cases, declare PassThroughOnException first and use WaitUntil for logging.
+
+### Setup
+
+This example worker is triggered by [Routes](https://developers.cloudflare.com/workers/platform/triggers/routes/). To try this example, add your site to cloudflare and add some records(A and CNAME, etc.) so that you can actually access the website.
+If your domain is `sub.example.com`, edit `wrangler.toml` as following:
+
+```toml
+routes = [
+    { pattern = "sub.example.com/*", zone_name = "example.com" }
+]
+```
+
+The workers is executed if the URL matches `sub.example.com/*`.
+
+### Development
+
+#### Requirements
+
+This project requires these tools to be installed globally.
+
+* wrangler
+* tinygo
+
+#### Commands
+
+```
+make dev     # run dev server
+make build   # build Go Wasm binary
+make publish # publish worker
+```

examples/fetch-event/main.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httputil"
+	"time"
+
+	"github.com/syumai/workers"
+	"github.com/syumai/workers/cloudflare"
+	"github.com/syumai/workers/cloudflare/fetch"
+)
+
+func handler(w http.ResponseWriter, req *http.Request) {
+	ctx := req.Context()
+
+	cloudflare.PassThroughOnException(ctx)
+
+	// logging after responding
+	cloudflare.WaitUntil(ctx, func() {
+		for i := 0; i < 5; i++ {
+			time.Sleep(time.Second)
+		}
+		fmt.Println("5-second task completed")
+	})
+
+	// panic if x-error header has provided
+	if req.Header.Get("x-error") != "" {
+		panic("error")
+	}
+
+	// responds with origin server
+	fc := fetch.NewClient()
+	proxy := httputil.ReverseProxy{
+		Transport: fc.HTTPClient().Transport,
+		Director: func(r *http.Request) {
+			r.URL = req.URL
+		},
+	}
+
+	proxy.ServeHTTP(w, req)
+}
+
+func main() {
+	workers.Serve(http.HandlerFunc(handler))
+}

examples/fetch-event/wrangler.toml

@@ -0,0 +1,10 @@
+name = "fetch-event"
+main = "./worker.mjs"
+compatibility_date = "2023-02-24"
+
+routes = [
+    { pattern = "example.com/*", zone_name = "example.com" }
+]
+
+[build]
+command = "make build"