問題內容
我正在 aws lambda 中使用 go 並尋找通用的中間件解決方案。我有以下程式碼：
func wshandler(ctx context.context, event events.apigatewaywebsocketproxyrequest) (events.apigatewayproxyresponse, error) {
}
type handlerfunc func(context.context, events.apigatewaywebsocketproxyrequest) (events.apigatewayproxyresponse, error)
func logmiddleware(next handlerfunc) handlerfunc {
return handlerfunc(func(ctx context.context, event events.apigatewaywebsocketproxyrequest) (events.apigatewayproxyresponse, error) {
return next(ctx, event)
})
}
lambda.start(logmiddleware(wshandler))
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中間件函數有一個參數 events.apigatewaywebsocketproxyrequest 因為目標處理程序 wshandler 使用此類型。
我有另一個處理程序，它採用參數 event events.apigatewayproxyrequest ，如下所示。由於參數不匹配，因此無法使用此中間件。
graphqlquerymutationhandler(ctx context.context, event events.apigatewayproxyrequest){
...
}
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我嘗試將中間件句柄更改為 interface{}，但不起作用。 go 抱怨這種類型。
type HandlerFunc func(context.Context, interface{}) (interface{}, error)
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有沒有辦法讓中間件適用於任何處理程序類型？
正確答案
讓我分享我能夠在我的系統上複製的工作解決方案。首先跟大家分享我使用的專案佈局：
events/
http_event.json
sqs_event.json
hello-world/
main.go
sqs/
main.go
middlewares/
middlewares.go
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現在，讓我們專注於程式碼。
middlewares/middlewares.go
#程式碼如下：
package middlewares
import (
"context"
"fmt"
"github.com/aws/aws-lambda-go/events"
)
type record struct {
events.apigatewayproxyrequest `json:",omitempty"`
events.sqsevent `json:",omitempty"`
}
type event struct {
records []record `json:"records"`
}
type handlerfunc func(ctx context.context, event event) (string, error)
func logmiddleware(ctx context.context, next handlerfunc) handlerfunc {
return handlerfunc(func(ctx context.context, event event) (string, error) {
fmt.println("log from middleware!")
return next(ctx, event)
})
}
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讓我們總結一下基本概念：
- 我們定義
event 結構體，它將成為我們的通用事件。它是 record 結構的包裝器。
record 結構體使用結構嵌入來嵌入我們要處理的所有事件（例如 event.apigatewayproxyrequest 和 sqsevent）。 - 我們依靠中間件簽名中的這一點來盡可能通用。
events/http_event.json
#
{
"records": [
{
"body": "{\"message\": \"hello world\"}",
"resource": "/hello",
"path": "/hello",
"httpmethod": "get",
"isbase64encoded": false,
"querystringparameters": {
"foo": "bar"
},
"pathparameters": {
"proxy": "/path/to/resource"
},
"stagevariables": {
"baz": "qux"
},
"headers": {
"accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
"accept-encoding": "gzip, deflate, sdch",
"accept-language": "en-us,en;q=0.8",
"cache-control": "max-age=0",
"cloudfront-forwarded-proto": "https",
"cloudfront-is-desktop-viewer": "true",
"cloudfront-is-mobile-viewer": "false",
"cloudfront-is-smarttv-viewer": "false",
"cloudfront-is-tablet-viewer": "false",
"cloudfront-viewer-country": "us",
"host": "1234567890.execute-api.us-east-1.amazonaws.com",
"upgrade-insecure-requests": "1",
"user-agent": "custom user agent string",
"via": "1.1 08f323deadbeefa7af34d5feb414ce27.cloudfront.net (cloudfront)",
"x-amz-cf-id": "cdehvqoznx43vyqb9j2-nvch-9z396uhbp027y2jvkcpnlmgjhqlaa==",
"x-forwarded-for": "127.0.0.1, 127.0.0.2",
"x-forwarded-port": "443",
"x-forwarded-proto": "https"
},
"requestcontext": {
"accountid": "123456789012",
"resourceid": "123456",
"stage": "prod",
"requestid": "c6af9ac6-7b61-11e6-9a41-93e8deadbeef",
"requesttime": "09/apr/2015:12:34:56 +0000",
"requesttimeepoch": 1428582896000,
"identity": {
"cognitoidentitypoolid": null,
"accountid": null,
"cognitoidentityid": null,
"caller": null,
"accesskey": null,
"sourceip": "127.0.0.1",
"cognitoauthenticationtype": null,
"cognitoauthenticationprovider": null,
"userarn": null,
"useragent": "custom user agent string",
"user": null
},
"path": "/prod/hello",
"resourcepath": "/hello",
"httpmethod": "get",
"apiid": "1234567890",
"protocol": "http/1.1"
}
}
]
}
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這裡沒什麼好說的。
events/sqs_event.json
#
{
"records": [
{
"records": [
{
"messageid": "19dd0b57-b21e-4ac1-bd88-01bbb068cb78",
"receipthandle": "messagereceipthandle",
"body": "my own event payload!",
"attributes": {
"approximatereceivecount": "1",
"senttimestamp": "1523232000000",
"senderid": "123456789012",
"approximatefirstreceivetimestamp": "1523232000001"
},
"messageattributes": {},
"md5ofbody": "4d1d0024b51659ad8c3725f9ba7e2471",
"eventsource": "aws:sqs",
"eventsourcearn": "arn:aws:sqs:us-east-1:123456789012:myqueue",
"awsregion": "us-east-1"
}
]
}
]
}
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這也適用於這裡。
hello-world/main.go
package main
import (
"context"
"fmt"
"httplambda/middlewares"
"github.com/aws/aws-lambda-go/lambda"
)
func lambdahandler(ctx context.context, event middlewares.event) (string, error) {
_ = ctx
fmt.println("path:", event.records[0].apigatewayproxyrequest.path)
fmt.println("hi from http-triggered lambda!")
return "", nil
}
func main() {
// start the lambda handler
lambda.start(middlewares.logmiddleware(context.background(), lambdahandler))
}
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請注意我們如何取得活動資訊。
sqs/main.go
package main
import (
"context"
"fmt"
"httplambda/middlewares"
"github.com/aws/aws-lambda-go/lambda"
)
func lambdaHandler(ctx context.Context, event middlewares.Event) (string, error) {
_ = ctx
fmt.Println("Queue name:", event.Records[0].SQSEvent.Records[0].EventSourceARN)
fmt.Println("Hi from SQS-triggered lambda!")
return "", nil
}
func main() {
lambda.Start(middlewares.LogMiddleware(context.Background(), lambdaHandler))
}
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決賽
有幾個注意事項要考慮：
- 在遵循此解決方案之前，我嘗試使用類型參數，但沒有成功。中間件的簽名中似乎不允許使用它們。
- 程式碼過於簡化，尚未做好生產準備。
如果這有幫助或您需要其他任何東西，請告訴我，謝謝！
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