20230126 Gophers Code Reading Party

// WrapHandlerWithListeners wraps a lambda handler, and calls listeners before and after every invocation.
func WrapHandlerWithListeners(handler interface{}, listeners ...HandlerListener) interface{} {
    err := validateHandler(handler)
    if err != nil {
        // This wasn't a valid handler function, pass back to AWS SDK to let it handle the error.
        logger.Error(fmt.Errorf("handler function was in format ddlambda doesn't recognize: %v", err))
        return handler
    }
    coldStart := true

    // Return custom handler, to be called once per invocation
    return func(ctx context.Context, msg json.RawMessage) (interface{}, error) {
        //nolint
        ctx = context.WithValue(ctx, "cold_start", coldStart)
        for _, listener := range listeners {
            ctx = listener.HandlerStarted(ctx, msg)
        }
        CurrentContext = ctx
        result, err := callHandler(ctx, msg, handler)
        for _, listener := range listeners {
            ctx = context.WithValue(ctx, extension.DdLambdaResponse, result)
            listener.HandlerFinished(ctx, err)
        }
        coldStart = false
        CurrentContext = nil
        return result, err
    }
}

budougumi0617 commented 1 year ago

遅延評価している。clientは最初に初期化するけれど、データが必要になるのはユーザーが書いた関数の実行後だから。 https://github.com/DataDog/datadog-lambda-go/blob/ff5fffbace038f9a2017e70ad7ce5c09ff601b9e/internal/metrics/api.go#L121-L134

func (cl *APIClient) decryptAPIKey(decrypter Decrypter, kmsAPIKey string) <-chan string {

    ch := make(chan string)

    go func() {
        result, err := decrypter.Decrypt(kmsAPIKey)
        if err != nil {
            logger.Error(fmt.Errorf("Couldn't decrypt api kms key %s", err))
        }
        ch <- result
        close(ch)
    }()
    return ch
}

basebank / gophers-code-reading-party

20230126 Gophers Code Reading Party #40

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