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Posted to dev@nutch.apache.org by "Koen Smets (JIRA)" <ji...@apache.org> on 2014/02/05 19:50:16 UTC
[jira] [Commented] (NUTCH-1679) UpdateDb using batchId, link may
override crawled page.
[ https://issues.apache.org/jira/browse/NUTCH-1679?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13892415#comment-13892415 ]
Koen Smets commented on NUTCH-1679:
-----------------------------------
I can confirm that this issue also occurs when using a Cassandra datastore.
Although, the `bin/crawl` script changed in [NUTCH-1556] only by adding the `$batchId` from the one in 2.2.1, this changes behaviour drastically. A lot of pages get refetched sooner than indicated by db.default.fetch.interval and outnumber the unfetched pages.
Although I noticed the remarkable speedup when focusing only on the pages from the current batch, I changed `$batchId` to `-all` in order to give preference to the pages that are truly fetched.
> UpdateDb using batchId, link may override crawled page.
> -------------------------------------------------------
>
> Key: NUTCH-1679
> URL: https://issues.apache.org/jira/browse/NUTCH-1679
> Project: Nutch
> Issue Type: Bug
> Affects Versions: 2.3
> Reporter: Tien Nguyen Manh
> Priority: Critical
> Fix For: 2.3
>
>
> The problem is in Hbase store, not sure about other store.
> Suppose at first crawl cycle we crawl link A, then get an outlink B.
> In second cycle we crawl link B which also has a link point to A
> In second updatedb we load only page B from store, and will add A as new link because it doesn't know A already exist in store and will override A.
> UpdateDb must be run without batchId or we must set additionsAllowed=false
> Here are code for new page
> page = new WebPage();
> schedule.initializeSchedule(url, page);
> page.setStatus(CrawlStatus.STATUS_UNFETCHED);
> try {
> scoringFilters.initialScore(url, page);
> } catch (ScoringFilterException e) {
> page.setScore(0.0f);
> }
> new page will override old page status, score, fetchTime, fetchInterval, retries, metadata[CASH_KEY]
> - i think we can change something here so that new page will only update one column for example 'link' and if it is really a new page, we can initialize all above fields in generator
> - or we add operator checkAndPut to store so when add new page we will check if already exist first
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