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Posted to httpclient-users@hc.apache.org by Dobri Kitipov <kd...@googlemail.com> on 2008/09/01 15:33:21 UTC
Re: "Keep-alive", stale connections and socket reuse
Hi Oleg,
thank you for the detailed answer of my question.
It seems we need to recommend the Axis2 guys to use the better version. Do
you know when there will be an official release of HttpClient 4.0-beta1?
Thank you,
Dobri
On Fri, Aug 29, 2008 at 2:11 PM, Oleg Kalnichevski <ol...@apache.org> wrote:
> On Thu, 2008-08-28 at 14:51 +0300, Dobri Kitipov wrote:
> > Hi,
> >
> > I am trying to explain myself how the "keep-alive", or TCP connection
> > persistence, is supposed to work? I have read several resources about
> that,
> > but I still have some questions (
> > http://java.sun.com/j2se/1.5.0/docs/guide/net/http-keepalive.html
> >
> > http://hc.apache.org/httpclient-3.x/performance.html
> >
> > http://www.io.com/~maus/HttpKeepAlive.html<http://www.io.com/%7Emaus/HttpKeepAlive.html>
> <http://www.io.com/%7Emaus/HttpKeepAlive.html>
> > ).
> >
> >
> >
> > How can I verify that "keep-alive" is really used? I know that for http
> 1.1
> > keep-alive is by default, but does it mean that the TCP socket is reused?
>
> Yes, it does.
>
> > I
> > mean how can I debug and verify that a TCP connection is reused. Does it
> > mean that a socket is reused?
> >
>
> Turning on the context logging would be one option.
>
> >
> >
> > I have executed several debug sessions using as a sample an Axis2 1.4
> > client, that in turns uses commons-httpclient-3.1.
> >
> > When I set client option:
> >
> >
> >
> > options.setProperty(HTTPConstants.REUSE_HTTP_CLIENT, "true");
> >
> >
> >
> > Having two web services invocations from my client I can see that the
> > HttpClient is really reused when the prop is set. The http connection
> used
> > is of type MultiThreadedHttpConnectionManager$HttpConnectionAdapter
> >
> > The problem is that here stale connection check is enabled, so when the
> > check is done as a consequence the connection (and its corresponding
> socket)
> > used is closed and a new one is opened.
> >
> >
>
> In some cases the stale connection check can report a perfectly valid
> connection as stale. I would strongly recommend disabling it.
>
>
> >
> > I can read from
> http://hc.apache.org/httpclient-3.x/preference-api.htmlthat:
> >
> >
> >
> > "Disabling stale connection check may result in *slight*
> > *performance*improvement at the risk of getting an I/O error when
> > executing a request
> > over a connection that has been closed at the server side."
> >
> >
> >
> > My general understanding is that in order to have a better performance a
> > connection should be reused and its socket,too?
> >
> >
>
> Yes.
>
> >
> > My question is if it is a bad practice to disable stale connection check
> in
> > order to reuse the connection and its socket?
>
> No, it is not. You just have to make sure your application can react
> intelligently to I/O exceptions caused by attempts to re-use a stale
> connection.
>
>
> > Why in commons-httpclient it
> > is preferred to close and open a new connection:
> >
>
> Only if a connection is believed to have been closed on the other end
> (is stale).
>
> >
> >
> >
> > Where I can read more about the benefit/tradeoff of having stale conn
> check?
> >
>
> It is recommended to have a reasonable recovery strategy or/and eviction
> policy for idle connections in place instead of relying on relatively
> expensive and not always reliable stale connection check.
>
> Hope this helps
>
> Oleg
>
> PS: You may also consider upgrading to HttpClient 4.0-beta1 which has a
> _much_ better and robust connection management code compared to
> HttpClient 3.x.
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: httpclient-users-unsubscribe@hc.apache.org
> For additional commands, e-mail: httpclient-users-help@hc.apache.org
>
>
Re: "Keep-alive", stale connections and socket reuse
Posted by Oleg Kalnichevski <ol...@apache.org>.
On Mon, 2008-09-01 at 16:33 +0300, Dobri Kitipov wrote:
> Hi Oleg,
> thank you for the detailed answer of my question.
> It seems we need to recommend the Axis2 guys to use the better version. Do
> you know when there will be an official release of HttpClient 4.0-beta1?
>
> Thank you,
> Dobri
>
HttpClient 4.0-beta1 has been officially released a few days ago.
You can get it here:
http://hc.apache.org/downloads.cgi
Unfortunately, Axis2 kernel is tightly coupled with HttpClient 3.1.
AXIS2-3933 [1] would need to be resolved first.
Oleg
[1] https://issues.apache.org/jira/browse/AXIS2-3933
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Re: "Keep-alive", stale connections and socket reuse
Posted by Dobri Kitipov <kd...@googlemail.com>.
Thank you for the answers!
Regards, Dobri
On Tue, Sep 2, 2008 at 9:20 PM, Oleg Kalnichevski <ol...@apache.org> wrote:
> On Mon, 2008-09-01 at 17:27 +0300, Dobri Kitipov wrote:
> > Hi Oleg,
> > I have one additional more abstract question. What I have observed during
> my
> > tests was that when I run my test scenarion with 5 WS consecutive
> > invocations and sniff the traffic I can see that the sockets were reused.
> > The problem is that when I first tried to debug the source it always
> invoked
> > the org.apache.commons.httpclient.HttpConnection isStale() method. This
> is
> > happening when there are more breakpoints set. If I set only a breakpoint
> > into the isStale() method then the socket is reused and no new connection
> is
> > opened for every invocation. It seems it is a timeout issue or a thread
> > issue to me? Do you suspect what may cause this? I have tried to set
> > SO_TIMEOUT and CONNECTION_TIMEOUT to 0, but without success. Any hints?
> >
>
> Not a slightest idea. It can well be the stale connection check just
> does not work reliably when run in the debug mode
>
> Oleg
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: httpclient-users-unsubscribe@hc.apache.org
> For additional commands, e-mail: httpclient-users-help@hc.apache.org
>
>
Re: "Keep-alive", stale connections and socket reuse
Posted by Oleg Kalnichevski <ol...@apache.org>.
On Mon, 2008-09-01 at 17:27 +0300, Dobri Kitipov wrote:
> Hi Oleg,
> I have one additional more abstract question. What I have observed during my
> tests was that when I run my test scenarion with 5 WS consecutive
> invocations and sniff the traffic I can see that the sockets were reused.
> The problem is that when I first tried to debug the source it always invoked
> the org.apache.commons.httpclient.HttpConnection isStale() method. This is
> happening when there are more breakpoints set. If I set only a breakpoint
> into the isStale() method then the socket is reused and no new connection is
> opened for every invocation. It seems it is a timeout issue or a thread
> issue to me? Do you suspect what may cause this? I have tried to set
> SO_TIMEOUT and CONNECTION_TIMEOUT to 0, but without success. Any hints?
>
Not a slightest idea. It can well be the stale connection check just
does not work reliably when run in the debug mode
Oleg
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Re: "Keep-alive", stale connections and socket reuse
Posted by Dobri Kitipov <kd...@googlemail.com>.
Hi Oleg,
I have one additional more abstract question. What I have observed during my
tests was that when I run my test scenarion with 5 WS consecutive
invocations and sniff the traffic I can see that the sockets were reused.
The problem is that when I first tried to debug the source it always invoked
the org.apache.commons.httpclient.HttpConnection isStale() method. This is
happening when there are more breakpoints set. If I set only a breakpoint
into the isStale() method then the socket is reused and no new connection is
opened for every invocation. It seems it is a timeout issue or a thread
issue to me? Do you suspect what may cause this? I have tried to set
SO_TIMEOUT and CONNECTION_TIMEOUT to 0, but without success. Any hints?
Thank you in advance.
Regards,
Dobri
On Mon, Sep 1, 2008 at 4:33 PM, Dobri Kitipov
<kd...@googlemail.com>wrote:
> Hi Oleg,
> thank you for the detailed answer of my question.
> It seems we need to recommend the Axis2 guys to use the better version. Do
> you know when there will be an official release of HttpClient 4.0-beta1?
>
> Thank you,
> Dobri
>
>
> On Fri, Aug 29, 2008 at 2:11 PM, Oleg Kalnichevski <ol...@apache.org>wrote:
>
>> On Thu, 2008-08-28 at 14:51 +0300, Dobri Kitipov wrote:
>> > Hi,
>> >
>> > I am trying to explain myself how the "keep-alive", or TCP connection
>> > persistence, is supposed to work? I have read several resources about
>> that,
>> > but I still have some questions (
>> > http://java.sun.com/j2se/1.5.0/docs/guide/net/http-keepalive.html
>> >
>> > http://hc.apache.org/httpclient-3.x/performance.html
>> >
>> > http://www.io.com/~maus/HttpKeepAlive.html<http://www.io.com/%7Emaus/HttpKeepAlive.html>
>> <http://www.io.com/%7Emaus/HttpKeepAlive.html>
>> > ).
>> >
>> >
>> >
>> > How can I verify that "keep-alive" is really used? I know that for http
>> 1.1
>> > keep-alive is by default, but does it mean that the TCP socket is
>> reused?
>>
>> Yes, it does.
>>
>> > I
>> > mean how can I debug and verify that a TCP connection is reused. Does it
>> > mean that a socket is reused?
>> >
>>
>> Turning on the context logging would be one option.
>>
>> >
>> >
>> > I have executed several debug sessions using as a sample an Axis2 1.4
>> > client, that in turns uses commons-httpclient-3.1.
>> >
>> > When I set client option:
>> >
>> >
>> >
>> > options.setProperty(HTTPConstants.REUSE_HTTP_CLIENT, "true");
>> >
>> >
>> >
>> > Having two web services invocations from my client I can see that the
>> > HttpClient is really reused when the prop is set. The http connection
>> used
>> > is of type MultiThreadedHttpConnectionManager$HttpConnectionAdapter
>> >
>> > The problem is that here stale connection check is enabled, so when the
>> > check is done as a consequence the connection (and its corresponding
>> socket)
>> > used is closed and a new one is opened.
>> >
>> >
>>
>> In some cases the stale connection check can report a perfectly valid
>> connection as stale. I would strongly recommend disabling it.
>>
>>
>> >
>> > I can read from
>> http://hc.apache.org/httpclient-3.x/preference-api.htmlthat:
>> >
>> >
>> >
>> > "Disabling stale connection check may result in *slight*
>> > *performance*improvement at the risk of getting an I/O error when
>> > executing a request
>> > over a connection that has been closed at the server side."
>> >
>> >
>> >
>> > My general understanding is that in order to have a better performance a
>> > connection should be reused and its socket,too?
>> >
>> >
>>
>> Yes.
>>
>> >
>> > My question is if it is a bad practice to disable stale connection check
>> in
>> > order to reuse the connection and its socket?
>>
>> No, it is not. You just have to make sure your application can react
>> intelligently to I/O exceptions caused by attempts to re-use a stale
>> connection.
>>
>>
>> > Why in commons-httpclient it
>> > is preferred to close and open a new connection:
>> >
>>
>> Only if a connection is believed to have been closed on the other end
>> (is stale).
>>
>> >
>> >
>> >
>> > Where I can read more about the benefit/tradeoff of having stale conn
>> check?
>> >
>>
>> It is recommended to have a reasonable recovery strategy or/and eviction
>> policy for idle connections in place instead of relying on relatively
>> expensive and not always reliable stale connection check.
>>
>> Hope this helps
>>
>> Oleg
>>
>> PS: You may also consider upgrading to HttpClient 4.0-beta1 which has a
>> _much_ better and robust connection management code compared to
>> HttpClient 3.x.
>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: httpclient-users-unsubscribe@hc.apache.org
>> For additional commands, e-mail: httpclient-users-help@hc.apache.org
>>
>>
>