问题内容
我正在 aws lambda 中使用 go 并寻找通用的中间件解决方案。我有以下代码：
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))
中间件函数有一个参数 events.apigatewaywebsocketproxyrequest 因为目标处理程序 wshandler 使用此类型。
我有另一个处理程序，它采用参数 event events.apigatewayproxyrequest ，如下所示。由于参数不匹配，因此无法使用此中间件。
graphqlquerymutationhandler(ctx context.context, event events.apigatewayproxyrequest){
...
}
我尝试将中间件句柄更改为 interface{}，但不起作用。 go 抱怨这种类型。
type HandlerFunc func(context.Context, interface{}) (interface{}, error)
有没有办法让中间件适用于任何处理程序类型？
正确答案
让我分享我能够在我的系统上复制的工作解决方案。首先给大家分享一下我使用的项目布局：
events/ http_event.json sqs_event.json hello-world/ main.go sqs/ main.go middlewares/ middlewares.go
现在，让我们关注代码。
middlewares/middlewares.go
代码如下：
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)
})
}
让我们总结一下基本概念：
- 我们定义
event结构体，它将成为我们的通用事件。它是record结构的包装器。 -
record结构使用结构嵌入来嵌入我们要处理的所有事件（例如event.apigatewayproxyrequest和sqsevent）。 - 我们依靠中间件签名中的这一点来尽可能通用。
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"
}
}
]
}
这里没什么可说的。
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"
}
]
}
]
}
这同样适用于这里。
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))
}
请注意我们如何获取活动信息。
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))
}
决赛
有几个注意事项需要考虑：
- 在遵循此解决方案之前，我尝试使用类型参数，但没有成功。中间件的签名中似乎不允许使用它们。
- 代码过于简化，且尚未做好生产准备。
如果这有帮助或者您需要其他任何东西，请告诉我，谢谢！
