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From Michael Becke <be...@u.washington.edu>
Subject Re: [PATCH] Fix for bug 16458
Date Fri, 21 Feb 2003 16:18:05 GMT
Sam,

I quite agree.  This could very well be what is happening for Aurelien.

One question.  Why is there no error when writing the request, but only 
when reading the response?  When I let the connection time out I always 
get a HttpRecoverableException in writeRequest().  This exception is 
caught and the method is retried.

Mike

Sam Maloney wrote:
> Hi,
> 
> This is what I have found, as I have worked in that area now:
> 
> The exception you speak is caused by fix for 16458. Before, instead of said 
> exception, you would have got 100% CPU * forever.
> 
> Here is the source of the exception (HttpMethodBase.java):
> 
> <SNIP>
> protected void readStatusLine(HttpState state, HttpConnection conn)
>     throws IOException, HttpRecoverableException, HttpException {
>         LOG.trace("enter HttpMethodBase.readStatusLine(HttpState, 
> HttpConnection)");
>         //read out the HTTP status string
>         String statusString = conn.readLine();
>         while ((statusString != null) && !statusString.startsWith("HTTP/")) {
>             statusString = conn.readLine();
>         }
>         if (statusString == null) {
>             // A null statusString means the connection was lost before we got 
> a
>             // response.  Try again.
>             throw new HttpRecoverableException("Error in parsing the status "
>                 + " line from the response: unable to find line starting with"
>                 + " \"HTTP/\"");
>         }
> 	...
> </SNIP>
> 
> Before fix for 16458, is was impossible to have a return value of null from 
> readLine(). Only an empty string would be returned.
> 
> The comment says the correct thing here, that the author expeced null return 
> to signify connection reset by peer/incorrect response.
> 
> The comment implies that somewhere up the call stack, the 
> HttpRecoverableException will be caught and the request automatically 
> retried, but I noticed it doesn't. Instead the exception gets to the main 
> thread.
> 
> I'm not sure if the code just hasn't been written to auto retry the request 
> when an HttpRecoverableException, or if it is broken, or if this is the way 
> intended, for the onus to be on the user of HttpClient to catch the exception 
> and try the request again. I'm sure someone more experienced with HttpClient 
> can answer that.
> 
> I think what makes sense as to what should happen is that any auto-retry code 
> (and remember, the HTTP RFC says only to retry once!) should be in 
> HttpClient.java. If the user uses the HttpConnection and HttpMethod classes 
> directly, then it would be up to the user to retry if they wanted to.
> 
> As for you Aurelien, you can simpy wrap your call to 
> HttpClient->executeMethod() like this:
> 
> for(int tries = 1; tries <= 2; tries++){
> 	try{
> 		client.executeMethod(...);
> 		break; // If success (no exception), then break.
> 	}catch(HttpRecoverableException re){
> 		if(tries == 2){
> 			throw re; // If this was try 2, then give up.
> 		}
> 	}catch(IOException ioe){
> 		throw new RuntimeException(".....", ioe);
> 	}
> }
> 
> To HttpClient developers:
> That above part of code should probably be put into HttpClient, as if the user 
> is using HttpClient, I think a recoverable error like the socket closing or 
> bad response should be auto retried, perhaps have a setting on HttpClient 
> (enableAutoRetry(bool) or something.)
> 
> Later,
> Sam Maloney
> 
> On Friday 21 February 2003 03:28, Aurelien Pernoud wrote:
> 
>>Weel, this one seems to be over (for me at least).
>>
>>But I'm sorry Mike, I found out my webapp was not logging httpexception
>>correctly (I catched it and logged it in debug mode and i was only logging
>>errors so...), I still have HttpRecoverable exception about "can't find
>>line starting with HTTP/" with multiple users.
>>
>>I'm gonna check my code again, try with the old httpclient, to see the
>>difference, and be sure of what it can come from.
>>
>>Aurelien Pernoud a écrit :
>>
>>>Made a test for 45 min, seems to be going fine now. I'll test
>>>furthermore tomorrow.
>>>
>>>Aurelien Pernoud a écrit :
>>>
>>>>Ok, I'm gonna test it right now and tell you tomorrow morning if
>>>>everything went ok with my app.
>>>>
>>>>Oleg Kalnichevski a écrit :
>>>>
>>>>>Committed
>>
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> 
> 
> 
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