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  1. Undertow
  2. UNDERTOW-2241

Undertow write-timeout can cause missing the last zero-length chunk in long polling

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      This issue can be reproduced in JBoss EAP 7.4.5 as the latest update.

      1. build attachment reproducer by maven

      cd long-polling
mvn package

      2. deploy the application

      cp target/ROOT.war jboss-eap-7.4/standalone/deployments/

      3. set write-timeout="5000" in standalone.xml

      <http-listener name="default" socket-binding="http" write-timeout="5000" redirect-socket="https" enable-http2="true"/>

      4. start packet capture on loopback by wireshark or tcpdump
      5. access http://127.0.0.1:8080/ with Chrome or Firefox
      6. After 10 seconds, long-polling timeout occurs and a response with missing zero chunks can be seen in pcap. A sample packet capture is attached.

      Show
      This issue can be reproduced in JBoss EAP 7.4.5 as the latest update. 1. build attachment reproducer by maven cd long-polling mvn package 2. deploy the application cp target/ROOT.war jboss-eap-7.4/standalone/deployments/ 3. set write-timeout="5000" in standalone.xml <http-listener name= " default " socket-binding= "http" write-timeout= "5000" redirect-socket= "https" enable-http2= " true " /> 4. start packet capture on loopback by wireshark or tcpdump 5. access http://127.0.0.1:8080/ with Chrome or Firefox 6. After 10 seconds, long-polling timeout occurs and a response with missing zero chunks can be seen in pcap. A sample packet capture is attached.
    • Hide
      • Set write-timeout longer than long-polling interval, or unset write-timeout. write-timeout is not set by default.
      • Avoid calling flush() from the servlet. If response type is Content-length: <byte>, this error does not occur.
      Show
      Set write-timeout longer than long-polling interval, or unset write-timeout. write-timeout is not set by default. Avoid calling flush() from the servlet. If response type is Content-length: <byte>, this error does not occur.

      Undertow write-timeout can cause closing a connection for a long-polling request without sending the last zero-length chunk like 0\r\n\r\n. This behavior causes a browser-side error, e.g. net::ERR_INCOMPLETE_CHUNKED_ENCODING in Google Chrome.

      In current Undertow implementation of write-timeout, for requests that re-use a keep-alive connection, the write-timeout set during the previous request processing is taken over to the next request. As a result, a zero chunk truncated response is returned if meet the following conditions are true:

      • The request re-use a keep-alive connection.
      • The request takes longer than write-timeout like long-polling processing by AsyncServlet.
      • Transfer-Encoding: chunked is applied to the response by calling flush() in the servlet.

      Even if the write-timeout is reached, it is expected to write the last chunk to the socket before closing a connection.

        1. Screenshot from 2023-03-15 13-13-45.png
          Screenshot from 2023-03-15 13-13-45.png
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            flaviarnn Flavia Rainone
            thofman Tomas Hofman
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              Created:
              Updated:
              Resolved: