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https://issues.apache.org/jira/browse/HTTPCLIENT-2136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17283709#comment-17283709
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Linda Werner commented on HTTPCLIENT-2136:
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Ok, we try to limit the keep-alive time. I opened the issue because I heard
problems from other customers on cloud networks (AWS) too. I thought maybe
Apache HTTPClient can implement a default behaviour, so that not every customer
has to troubleshoot this problem and make the correct settings. For small
product teams which only implement some features and do not know how the http
and tcp connection flow works this is a bad situation I think.
> Idle HTTP connections remain open
> ----------------------------------
>
> Key: HTTPCLIENT-2136
> URL: https://issues.apache.org/jira/browse/HTTPCLIENT-2136
> Project: HttpComponents HttpClient
> Issue Type: Improvement
> Components: HttpClient (classic)
> Affects Versions: 4.5.13
> Reporter: Linda Werner
> Priority: Minor
>
> We found out, that Apache HTTPClient sends HTTP header "Connection:
> keep-alive" by default.
> This behaviour can cause problems on some networks (e.g. Azure network).
> For our implementation we use Spring RestTemplate in combination with Apache
> HTTPClient (to support PATCH http requests). As soon as we used Apache
> HTTPClient we had trouble with some connections, but only on the Azure App
> Service (Azure network) - not locally.
> Our backend app opens connections to other services which are not closed, so
> the tcp connection remains open. The opposition sends tcp FIN after some
> minutes (5 minutes in our case), but the tcp FIN never reaches our app
> service. Something in the Azure network kills the idle tcp connection, but
> the application still holds the damaged tcp connections and tries to send
> data. With no socket read timeout implemented some unspecific time later the
> following exception occurs: "java.net.SocketException: Operation timed out
> (Read failed)". With configured socket read timeout the data read timeout
> exception occurs after the defined time, but this doesn't solve the main
> reason of the broken tcp connection.
> We found some workaround solutions like a connection pool which close idle
> connections after 3 minutes. But in our case we don't want the default
> behaviour to keep all connections open with keep-alive. Our final
> implementation is to set the HTTP header field "Connection: close".
> I think "keep-alive" is not a good default value for the HTTP header field
> "Connection".
> We heard that this issue happens on other networks (AWS), too. It seems to be
> a common practice to close idle connections in networks which use SNAT port
> allocation.
>
>
>
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