Use oplog_replay option to optimize queries on oplog #3
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…ce index on capped collections don't work so well...
…ast mark point when mmm crashes
gukoff
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Aug 15, 2017
gukoff
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gukoff
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It is straight up wrong in so many ways.
Isn't this enough?
q = self._oplog.find(
spec, tailable=True, await_data=True, oplog_replay=True
)| @@ -1,16 +1,16 @@ | |||
| #!/usr/bin/env python | |||
| #!/usr/bin/python | |||
| # for name,m in masters.items(): | ||
| # pprint.pprint(name) | ||
| # pprint.pprint(m._coll) | ||
| # pprint.pprint('masters output') |
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There shouldn't be any commented code. If you don't use it, remove it.
| '''Create a bson.Timestamp. Factored into a method so we can delay | ||
| importing socket until gevent.monkey.patch_all() is called. You could | ||
| also insert another timestamp function to set options if you so desire. | ||
| ''' |
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Here is a clear reason not to remove this method.
| master_uri = self._topology[name_by_id[master['_id']]]['uri'] | ||
| conn = Connection(master_uri) | ||
| coll = conn.local[MMM_DB_NAME] | ||
| for cp in coll.find(dict(_id='master_checkpoint')): |
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Don't use dict for it: {'_id': 'master_checkpoint'}
| if masters[s._topology[name]['id']] == True: | ||
| masters[s._topology[name]['id']] = s | ||
| except: | ||
| True |
| try: | ||
| if masters[s._topology[name]['id']] == True: | ||
| masters[s._topology[name]['id']] = s | ||
| except: |
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Using an index on the oplog is not very efficient and degrades performance when a big number of writes are being performed in a short amount of time.
Mongo has an internal scheme to perform queries on the oplog that are activated when using the "oplog_replay" option with queries (bit num 3 on http://www.mongodb.org/display/DOCS/Mongo+Wire+Protocol#MongoWireProtocol-OPQUERY).
pymongo doesn't, as yet, allow for the option, although a similar pull-request was proposed for this very purpose.
Please consider applying this patch if pymongo updates the available options in the Cursor class init.
Thx :)