I have a Spring Boot backend and I have just solved "ERR_CONNECTION_RESET", when uploading a file from Angular frontend, by configuring maxSwallowSize Tomcat property. I'm trying to understand what it does exactly. Tomcat documentation is not obvious to me:

The maximum number of request body bytes (excluding transfer encoding overhead) that will be swallowed by Tomcat for an aborted upload. An aborted upload is when Tomcat knows that the request body is going to be ignored but the client still sends it. If Tomcat does not swallow the body the client is unlikely to see the response. If not specified the default of 2097152 (2 megabytes) will be used. A value of less than zero indicates that no limit should be enforced.

https://tomcat.apache.org/tomcat-8.0-doc/config/http.html

Can I get some help?

CodePudding user response：

If your servlet's service() method exits (normally or exceptionally) without consuming the whole client's request body, Tomcat will still accept maxSwallowSize bytes before resetting the connection. This is required since most browsers read the server's response only after they sent the entire request (cf. this question).

To consume the requests body you need to:

• if the request is encoded as application/x-www-form-urlencoded, you need to call one of the getParameter* methods,
• if the request is encoded as multipart/form-data, you need to call one of the getPart* methods,
• in all other cases you need to read the entire InputStream.

An unconsumed request body is usually caused by errors, including those in the parsing of parameters or form parts.