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We have to take special care with our use of HTTP as it was not necessarily designed for our use case. Importantly, we don't want to close connections, because we really need and want to reuse them. This means we don't want to close Servlet response streams or use response.sendError calls. Instead we should return a error to the client in the format it asks Solr for as well as the proper response code. We also don't want to flush the response because it will interfere with chunked encoding. We also want to avoid our clients running into stale connections (they hit connection reset exception) - with HTTP 1.1 we can only do this by having the Jetty idle timeout higher the client idle timeout so that the clients control the connection. The other options involving trying to detect a stale connection involve an intrinsic race and are not good enough for our use case.

HTTP HTTP2 does not have this race problem and has much hardier connections that multiple requests can be multiplexed over. Solr currently uses a combination of HTTP1.1 and 2.

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