Re: Reuse of HTTPClient among different invocations is ok, what about different Web Services, hosts?

[Dobri Kitipov]

Thank you for the fast response Oleg :)
thanks,
dobri

On Thu, Mar 19, 2009 at 3:06 PM, Oleg Kalnichevski  wrote:

> On Thu, 2009-03-19 at 14:13 +0200, Dobri Kitipov wrote:
> > Hi everybody,
> > when we reuse HTTPClient underneath each subsequent call to
> > HttpClient.executeMethod() will go to the connection manager
> > (MultiThreadedHttpConnectionManager) and ask for an instance of
> > HttpConnection. I have tested some use cases when a HTTPClient is reused
> for
> > invocation of a single WS and I can verify there is socket reuse. So far
> so
> > good.
> >
> > Anyway, my question is: could we expect any problems when reusing
> HTTPClient
> > among different threads calling different WSs which are deployed at
> > different hosts/servers?
>
> HttpClient is fully thread-safe when used with a thread-safe connection
> manager.
>
>
> > As stated at - http://hc.apache.org/httpclient-3.x/threading.html -
> there is
> > a test case that demonstrates how HTTPClient can be reused among
> different
> > threads which in turn invoke different web services (WSs). My concern is
> > that HTTPClient has HttpState which I am not sure could be reused/shared
> > among different WSs invocations (JavaDoc says for HttpState: "A container
> > for HTTP attributes that may persist from request to request, such as
> {...@link
> > Cookie cookies} and authentication {...@link Credentials credentials}.")?
> Can
> > different WS clients share one HttpClient and its HttpState among
> different
> > threads and invoking different WSs (e.g. at differnet hosts)?
> >
>
> Yes, they can. Maintain a separate instance of HttpState per execution
> thread and pass it as a parameter to the HttpClient#executeMethod
>
> Hope this helps
>
> Oleg
>
>
> > Thank you in advance,
> > Dobri
>
>
> -
> To unsubscribe, e-mail: httpclient-users-unsubscr...@hc.apache.org
> For additional commands, e-mail: httpclient-users-h...@hc.apache.org
>
>

Reuse of HTTPClient among different invocations is ok, what about different Web Services, hosts?

[Dobri Kitipov]

Hi everybody,
when we reuse HTTPClient underneath each subsequent call to
HttpClient.executeMethod() will go to the connection manager
(MultiThreadedHttpConnectionManager) and ask for an instance of
HttpConnection. I have tested some use cases when a HTTPClient is reused for
invocation of a single WS and I can verify there is socket reuse. So far so
good.

Anyway, my question is: could we expect any problems when reusing HTTPClient
among different threads calling different WSs which are deployed at
different hosts/servers?
As stated at - http://hc.apache.org/httpclient-3.x/threading.html - there is
a test case that demonstrates how HTTPClient can be reused among different
threads which in turn invoke different web services (WSs). My concern is
that HTTPClient has HttpState which I am not sure could be reused/shared
among different WSs invocations (JavaDoc says for HttpState: "A container
for HTTP attributes that may persist from request to request, such as {...@link
Cookie cookies} and authentication {...@link Credentials credentials}.")? Can
different WS clients share one HttpClient and its HttpState among different
threads and invoking different WSs (e.g. at differnet hosts)?

Thank you in advance,
Dobri

Re: "Keep-alive", stale connections and socket reuse

[Dobri Kitipov]

Thank you for the answers!

Regards, Dobri

On Tue, Sep 2, 2008 at 9:20 PM, Oleg Kalnichevski <[EMAIL PROTECTED]> 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: [EMAIL PROTECTED]
> For additional commands, e-mail: [EMAIL PROTECTED]
>
>

Re: "Keep-alive", stale connections and socket reuse

[Dobri Kitipov]

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
<[EMAIL PROTECTED]>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 <[EMAIL PROTECTED]>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: [EMAIL PROTECTED]
>> For additional commands, e-mail: [EMAIL PROTECTED]
>>
>>
>

Re: "Keep-alive", stale connections and socket reuse

[Dobri Kitipov]

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 <[EMAIL PROTECTED]> 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: [EMAIL PROTECTED]
> For additional commands, e-mail: [EMAIL PROTECTED]
>
>

"Keep-alive", stale connections and socket reuse

[Dobri Kitipov]

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
).



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? I
mean how can I debug and verify that a TCP connection is reused. Does it
mean that a socket is reused?



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.



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?



My question is if it is a bad practice to disable stale connection check in
order to reuse the connection and its socket? Why in commons-httpclient it
is preferred to close and open a new connection:



org.apache.commons.httpclient HttpMethodDirector



private void executeWithRetry(final HttpMethod method):

….

   if (this.conn.getParams().isStaleCheckingEnabled()) {

this.conn.closeIfStale(); - this is executed

}

….



Where I can read more about the benefit/tradeoff of having stale conn check?

I will appreciate any information on the topic, because I have no much
knowledge into this field.



Thank you in advance,

Dobri