Dear Hailong, The frontend will ask the summary for the top documents. A backend node will receive a getSummary request for every top document it owns. You can go through the logs of the backend node and verify that the node does receive getSummary requests.
Regards, -Stavros. ________________________________________ From: Hailong Yang [[email protected]] Sent: Monday, October 22, 2012 10:38 AM To: Volos Stavros Cc: [email protected]; Lingjia Tang; Jason Mars Subject: Re: How to fit the index into the memory for the web search benchmark Dear Stavros, I am confused why we need to bring the segments into memory. I examined the log file from the front end server which recorded the queries sent to and responses received from the nutch server. The log file showed the nutch server only replied how many hits were found in the crawled dataset without being asked for the details of the page contents. So that means when orchestrating the searching, the object NutchBean never needs to call the method getSummary that accesses the segments to retrieve the page contents. That is also to say we don't need to care about whether the size of the segments could be able to fit into the memory for this specific web search workload in CloudSuite, right? Please Correct me if I am wrong. Best Hailong On Sun, Oct 21, 2012 at 9:04 AM, Volos Stavros <[email protected]<mailto:[email protected]>> wrote: Dear Hailong, The reason you get I/O activity is due to the fact that the segments don't fit into the memory. I would recommend reducing the size of your index so that indexes+segments occupy roughly 16GB. This is relatively easy to do in case you used multiple reducer tasks (during the crawling phase) to create multiple partitions. (see Notes at http://parsa.epfl.ch/cloudsuite/search.html: The mapred.reduce.tasks property determines how many index and segment partitions will be created.) Regards, -Stavros. ________________________________________ From: Hailong Yang [[email protected]<mailto:[email protected]>] Sent: Friday, October 19, 2012 8:03 PM To: Volos Stavros Cc: [email protected]<mailto:[email protected]>; Lingjia Tang; Jason Mars Subject: Re: How to fit the index into the memory for the web search benchmark Dear Stavros, Thank you for your reply. I understand the data structures required during the search. The 6GB is only the size of the actual index ( the directory of indexes). The whole data including the segments accounts for 30GB. Best Hailong On Fri, Oct 19, 2012 at 9:03 AM, Volos Stavros <[email protected]<mailto:[email protected]><mailto:[email protected]<mailto:[email protected]>>> wrote: Dear Hailong, There are two components that are used when performing a query against the index serving node: (a) the actual index (under indexes) (b) segments (under segments) What exactly is 6GB? Are you including the segments as well? Regards, -Stavros. ________________________________________ From: Hailong Yang [[email protected]<mailto:[email protected]><mailto:[email protected]<mailto:[email protected]>>] Sent: Wednesday, October 17, 2012 4:51 AM To: [email protected]<mailto:[email protected]><mailto:[email protected]<mailto:[email protected]>> Cc: Lingjia Tang; Jason Mars Subject: How to fit the index into the memory for the web search benchmark Hi CloudSuite, I am experimenting with the web search benchmark. However, I am wondering how to fit the index into the memory in order to avoid unnecessary disk access. I have a 6GB index crawled from wikipedia and the RAM is 16GB. During the workload execution, I noticed there were periodical 2% I/O utilization increase and the memory used by nutch server was always less than 500MB. So I guess the whole index is not brought into the memory by default before serving the search queries, right? Could you tell me how to do that exactly as you did in the clearing cloud paper. Thanks! Best Hailong
