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7.05.Stream.md

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Stream

Most Easegress traffic is message-based, but Easegress v2 pipeline is protocol independent, that's it supports stream-based traffic like TCP, and there's stream traffic even in HTTP.

Another new feature in Easegress v2 is multiple requests/responses support, this requires the payload of a request/response can be read more than once, for message-based traffic, this is simple and easy to do, as Easegress can read the full message payload into memory. But for stream-based traffic, this is impossible, as the payload may require too much memory, and/or take too much time to read it into memory.

To resolve the above issue, Easegress allow user or developer to configure whether a request/response is a stream, for example:

  • We can set clientMaxBodySize of an HTTP server to a negative value to tell Easegress the request is a stream, and not a stream otherwise. Please refer HTTPServer for more information.
  • We can set serverMaxBodySize of a Proxy filter to a negative value to tell Easegress the response is a stream, and not a stream otherwise. Please refer Proxy for more information.

As we have mentioned above, the payload of a stream-based request/response can only be read once, so some features are not possible for these requests/responses, including:

  • In the template of RequestBuilder or ResponseBuilder, you cannot access the payload(in HTTP, the body) of an existing stream-based request/response, while it is fine to access other information of the request/response.
  • Stream-based request/response cannot be cached by Proxy.
  • The HeaderToJSON filter does not support stream-based requests/responses.
  • You cannot access the payload of stream-based request/response in a WasmHost filter.