Why does my function "hangs"

Question

def retCursor():
    host = "localhost"
    user = "disappearedng"

    db = "gupan_crawling3"
    conn = MySQLdb.connect( host=host, user=user, passwd=passwd, db=db)
    cursor = conn.cursor()
    return cursor
singleCur = retCursor()


def checkTemplateBuilt(netlocH):
    """Used by crawler specifically, this check directly whether template has been built"""
    singleCur.execute( """SELECT templateBuilt FROM templateEnough WHERE netloc=%s""", [ netlocH])
    r = singleCur.fetchone()
    if r:
        if bool( r[0]):
            return True
    return False

Hi everyone I am currently using MySQLdb. For some reason, after perhaps 30 mins of running my app comes to a complete halt. It appears that this function is blocking me. (DOn't know for what reason)

Traceback (most recent call last):
  File "/usr/lib/python2.6/multiprocessing/process.py", line 231, in _bootstrap
    self.run()
  File "/mount/950gb/gupan5/disappearedng_temp/code_temp_NEWBRANCH/gupan5-yahoo/crawling/templateCrawling/TemplateCrawler/crawler/crawler.py", line 117, in run
    self.get_check_put()
  File "/mount/950gb/gupan5/disappearedng_temp/code_temp_NEWBRANCH/gupan5-yahoo/crawling/templateCrawling/TemplateCrawler/crawler/crawler.py", line 66, in get_check_put
    if not self.checkLinkCrawlability(linkS, priority):
  File "/mount/950gb/gupan5/disappearedng_temp/code_temp_NEWBRANCH/gupan5-yahoo/crawling/templateCrawling/TemplateCrawler/crawler/crawler.py", line 53, in checkLinkCrawlability
    if checkTemplateBuilt( getNetLoc( link)):
  File "/mount/950gb/gupan5/disappearedng_temp/code_temp_NEWBRANCH/gupan5-yahoo/crawling/templateCrawling/TemplateCrawler/publicapi/publicfunc.py", line 71, in checkTemplateBuilt
    singleCur.execute( """SELECT templateBuilt FROM templateEnough WHERE netloc=%s""", [ netlocH])
  File "/var/lib/python-support/python2.6/MySQLdb/cursors.py", line 153, in execute
    r = self._query(query)
KeyboardInterrupt

Btw this is the table:

CREATE TABLE templateEnough( 
    `netloc` INT(32) unsigned NOT NULL,   
    `count` SMALLINT(32) unsigned NOT NULL,
    `templateBuilt` TINYINT(1) unsigned DEFAULT 0 NOT NULL,
    PRIMARY KEY ( netloc )
) ENGINE=MEMORY DEFAULT CHARSET=utf8
;

Any ideas?

Answer 1

According to your traceback, you interrupted the script during the execution of checkTemplateBuilt, not enoughPassedForTemplate.

I think the problem lies in a different part of the code; maybe there is an infinite loop somewhere? Maybe in the run function?

Answer 2

There might be a lock on the table preventing the query from completing.

Answer 3

Try logging the query string to a file right before you execute it. Then when you think it is hung, you can look at the query and see if it works manually