Spike: Add optional retry middleware #51
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pkg/proxy/middleware.go
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| for i := 0; ; i++ { | ||
| capturedResp = &responseBuffer{ | ||
| header: make(http.Header), | ||
| body: bytes.NewBuffer([]byte{}), |
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As we spoke about, I think it would be good to know whether we are adding to in-memory buffering or not by doing this. I think it is still worth having this feature even if we are making memory requirements worse. This makes me think that we might actually want to make retrying configurable:
- enabled/disabled
- list of status codes to retry? maybe this configurable item would be excessive?
pkg/proxy/handler.go
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| if err != nil { | ||
| return "", r, nil | ||
| var body []byte | ||
| if mb, ok := r.Body.(*lazyBodyCapturer); ok && mb.capturedBody != nil { |
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What is this change doing?
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With this change, I am re-using the buffer of the retry middleware so that the body must not be re-read (and buffered) again. It is an optimization
pkg/proxy/middleware.go
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| return d | ||
| } | ||
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| func (r *responseWriterDelegator) discardedResponse() bool { |
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Seems like this method could go away in favor of just checking r.discardErrResp?
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I need this to satisfy the response type in newResponseWriterDelegator() xResponseWriter. The source writer either implements ReaderFrom or not. So does the returned implementation.
| headerBuf: make(http.Header), | ||
| discardErrResp: discardErrResp, // abort early on timeout, context cancel | ||
| } | ||
| if _, ok := writer.(io.ReaderFrom); ok { |
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In Lingo when would the writer be an io.ReaderFrom and when would it not be?
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The response type in the Go stdlib implements the interface. So should do all decorators to make use of internal or future optimizations. it is used in io.Copy for example. I saw a presentation once but I don't have the link anymore. I also double checked with the prometheus decorator to ensure it is still a good practice
Same for WriteTo on the lazyBodyCapturerWriteTo
| // If the maximum number of retries is 0, it returns the next handler without adding any retries. | ||
| // If the list of retryable status codes is empty, it uses a default set of status codes (http.StatusBadGateway, http.StatusServiceUnavailable, http.StatusGatewayTimeout). | ||
| // The function creates a RetryMiddleware struct with the given parameters and returns it as an http.Handler. | ||
| func NewRetryMiddleware(maxRetries int, other http.Handler, optRetryStatusCodes ...int) http.Handler { |
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We need to limit the max bytes read. See https://cwe.mitre.org/data/definitions/400.html example 6
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I can see this being useful.
alpe
changed the title
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Closing this now in favour of #61 |
Resolves #48
the implementation is based on 2 elements:
not considered is a priority queue for retries