[GSS](7.4.z) UNDERTOW-2228 - Undertow write-timeout can cause a truncate response for request coming through keep-alive connection

1. Configure write-timeout on http-lister (and ajp-listener) in undertow subsystem. For example: <subsystem xmlns= "urn:jboss:domain:undertow:12.0" ...> ...(snip)... <server name= " default -server" > <http-listener name= " default " socket-binding= "http" redirect-socket= "https" enable-http2= " true " record-request-start-time= " true " write-timeout= "5000" /> <ajp-listener name= "ajp" socket-binding= "ajp" record-request-start-time= " true " write-timeout= "5000" /> <https-listener name= "https" socket-binding= "https" security-realm= "ApplicationRealm" enable-http2= " true " /> <host name= " default -host" alias= "localhost" > <location name= "/" handler= "welcome-content" /> <http-invoker security-realm= "ApplicationRealm" /> <access-log pattern= "%h %l %u %t &quot;%r&quot; %s %b %I %S %T" /> </host> </server> ...(snip)... </subsystem> 2. Deploy a war that contains the following example.jsp which write larger response than the default buffer size (16KB) and emulate long request processing with Thread.sleep(): <% System .out.println( "example.jsp - start" ); // int size = 8 * 1024; // 8KB int size = 16 * 1024; // 16KB - default buffer size char [] buffer = new char [size]; for ( int i = 0; i < size; i++) { buffer[i] = 'X' ; } try { // emulate long request processing System .out.println( "sleep 10 seconds" ); Thread .sleep(10*1000L); } catch (Exception ignore) {} out.print( "start" ); // out.flush(); out.write(buffer); out.print( "end" ); System .out.println( "example.jsp - end" ); %> 3. Use the following curl command to send a single request to example.jsp $ curl -v http: //127.0.0.1:8080/example/example.jsp This request can be processed successfully and the response contains all content ("start" + 16KB size of "X" + "end") 4. Use the following curl command to send two requests (1st one for the welcome content and 2nd one for example.jsp), so the 2nd request for example.jsp will be sent through the same keep-alive connection. Please make sure that execute the following command in one line. $ curl -v http: //127.0.0.1:8080/ http://127.0.0.1:8080/example/example.jsp Then, you will see that the curl command shows "curl: (18) transfer closed with outstanding read data remaining" on the 2nd request for example.jsp. And the response is truncated in the middle of 16KB size of "X", so you do not see the last "end" in the response. If you enable (uncomment) "out.flush()" in the above example.jsp, the response is truncated before 16KB size of "X", so you see only the first "start" in the response. — Another easy step to reproduce with web browser. This reproducer does not need "Thread.sleep()" in the application. 1. Deploy a war that contains the following example2.jsp which write larger response than the default buffer size (16KB): <% System .out.println( "example.jsp - start" ); // int size = 8 * 1024; // 8KB int size = 16 * 1024; // 16KB - default buffer size char [] buffer = new char [size]; for ( int i = 0; i < size; i++) { buffer[i] = 'X' ; } out.println( "start" ); // out.flush(); out.write(buffer); out.println(); out.println( "end" ); System .out.println( "example.jsp - end" ); %> 2. Access example2.jsp with web browser $ curl -v http: //127.0.0.1:8080/example/example.jsp This request can be processed successfully and the response contains all content ("start" + 16KB size of "X" + "end") 3. Wait for several seconds like 10 seconds which is longer than configure write-timeout (5000 = 5 seconds in this case) and is shorter than the default no-request-timeout (60000 = 60 seconds) 4. Reload the previews page to access the same example2.jsp again through the same keep-alive connection. You will see the response is truncated in the middle of 16KB size of "X", so you do not see the last "end" in the response. If you enable (uncomment) "out.flush()" in the above jsp, the response is truncated before 16KB size of "X", so you see only the first "start" in the response.