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From "none none" <kor...@lycos.com>
Subject RE: Crash / Recovery Scenario
Date Mon, 08 Jul 2002 19:05:09 GMT
 If you tell me the computer doesn't crash , the only thing is you want to stop safely the
process, well , in this case the Manager will not stop until the task is not complete, because
i am running the Manager as an NT service ,i have a little problem here, you cannot stop a
thread while it is doing I/O operation like recursively scan of a directory, you have to wait
a little bit.
 I see that you are looking for software stability, but software is strictly related with
hardware, you need a good hardware too, think about a RAID structure, 0 or 5 depends, think
about a clustered system.
This depends what you want from your search engine.
Also i think is good focus on have a good cache status, e.g.: if i have a bad error and i
can't recover the index i rebuild it by calling a method that scan all my cache, it is no
great but better than nothing . Also i never had that kind of problem.
Also adopt a multi threaded will improve by 40% the actual speed, you need to merge all the
segments at the end. (i tested just with 2 thread on Win2K).
If you are looking for a search engine like google, there is a lot of work to do, A LOT!!!!
My opinion is to split index and cache on 'n' machine , but the only thing i don't know how
to do it's run a search on multiple index on multiple machine, with sockets will not work,
sockets become really slow with heavy traffic, i was thinking on a Java compatible DLL able
to merge multiple machine as a logical unit.

ciao.


--

On Mon, 8 Jul 2002 21:07:32   
 Nader S. Henein wrote:
>brilliant .. I was thinking along the same lines, a new issue that I'm
>facing is just lucene dying on me, in the middle of indexing .. no server
>crash .. nothing .. what do you do if it just stops mid-indexing ?
>
>-----Original Message-----
>From: none none [mailto:korfut@lycos.com]
>Sent: Monday, July 08, 2002 8:42 PM
>To: nsh@bayt.net
>Subject: Re: Crash / Recovery Scenario
>
>
> hi, i do perform the same things as you do, but i do that everytime i got a
>NullPointerException when i try to run a search . If this happen i try to
>reopen the index searcher, if i got an exception here i sleep for 500 ms
>then i try again, after 5 times i generate a servlet exception. Concerning
>the delete of write.lock and commit.lock, i use a manager,what it does is
>execute different kind of operation in blocks, like 100 or 1000.
>Each operation can be:
>1.Delete documents
>2.Add documents
>3.Search document/s
>
>A combination of this 3 operation allow me to "update" the index with
>searches still running. But there is a problem "versioning", between current
>cache of documents and current version of "INDEXED" documents, during update
>you can search for something that is found in the index but that has been
>updated in the cache, so i have a bounch of documents duplicate during that,
>and at the end i notify using a RMI callback all the clients connected to
>that Manager to re open the index, then i clean up all this duplicate. At
>this stage i have still an error in case the Manager die because i have all
>in memory, but i did a little work around to handle that. My next step is
>make this "transaction" persistent, so i can recovery the previous "status".
>
>Every time i run an operation as listed above i do a check if "write.lock"
>or "commit.lock" exists, in that case i call the unlock() method, i delete
>them (if the method unlock doesn't), then i optimize the index.
>
>Until now everything seems to work fine.
>ciao.
>
>--
>
>On Mon, 8 Jul 2002 09:40:10
> Nader S. Henein wrote:
>>
>>I'm currently using Lucene to sift through about a million documents, I've
>>written a servlet to do the indexing and the searching, the servlets are
>ran
>>through resin, The Crash scenario I'm thinking of is a web server crash (
>>for a million possible reasons ) while the index is being updated or
>>optimized, what I've noticed is the creation of write.lock and commit.lock
>>files witch stop further indexing because the application thinks that the
>>previously scheduled indexer is still running (witch could very well be
>true
>>depending on the size of the update). This is the recovery I have in mind
>>but I think it might be somewhat of a hack, On restart of the web server
>>I've written an Init function that checks for write.lock or commit.lock ,
>>and if either exist it deletes both of them and optimizes the index. Am I
>>forgetting anything ? is this wrong ? is there a Lucene specific way of
>>doing this like running the optimizer with a specific setup.
>>
>>Nader S. Henein
>>Bayt.com , Dubai Internet City
>>Tel. +9714 3911900
>>Fax. +9714 3911915
>>GSM. +9715 05659557
>>www.bayt.com
>>
>>
>>--
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>>
>>
>
>
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