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Scaleable Page Counter
A gentle introduction to software engineering at Google scale
Jon Tirsen, Google
Monday, October 4, 2010
We’ve had visitors!
Monday, October 4, 2010
Scaleable Page Counter A gentle introduction to software - - PowerPoint PPT Presentation
Scaleable Page Counter A gentle introduction to software - - PowerPoint PPT Presentation
Scaleable Page Counter A gentle introduction to software engineering at Google scale Jon Tirsen, Google Monday, October 4, 2010 Weve had visitors! Monday, October 4, 2010 Monday, October 4, 2010 Monday, October 4, 2010 Monday, October
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Front End Counter Front End Front End Front End Front End Front End Front End Front End Front End +1 112
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Front End Counter Front End Front End Front End Front End Front End Front End Front End Front End Counter Counter
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Front End Counter Counter Counter Write Shard by: random
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Front End Counter Counter Counter Read fan out
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Blocking reads Front end Counter Counter Counter
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Async reads Front end Counter Counter Counter
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Front End Counter Counter Counter Write
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Front End Counter Counter Counter Read
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Availability
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Availability Number of shards 99% 1 1000 14 mins/day 7 hours/month = 3 days/year
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Availability Number of shards
Writing
99% 99.9999...% 1 1000
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Availability Number of shards
Read fan out
1 1000 99% 0.004% 0.6% 60%
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Replica Front End Counter Counter Counter Write Reads Replica Replicas Replica Replica Replicas Replica Replica Replicas Update
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Availability Number of shards
Read fan out to 5 replicas
1 1000 8 nines 5 nines 6 nines 99.99%
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Front End Counter Counter Counter Read & Cache Write & Read
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Availability Number of shards
Read fan out with caching
99% 99.9999...% 1 1000
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Consistency
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Write Write Write Write Read Probability
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Write Write Write Write Read Probability
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Write Write Write Write Probability Read
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Front End 52
200 Cached: 299
299
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Front End 52
200 Cached: 299, 52
299
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Front End 56
200 Cached: 299, 52
299
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Front End 56
200 Cached: 299, 52
302
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Front End 56
201 Cached: 299, 52
302 +1 552 =299+52+
2 1
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A different solution...
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Analyser
Read & sum
Logs Analyser Analysers Front End Front End Front End Logs Logs
Append
Push new count
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Front End Analyser Log Front End Counter
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Analyser Front End Front End Front End Push new count
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Sharding Shard selection: random, by user, by document Fan out: writes, reads Replication/Caching Consistency model: eventual, shard local Sync -> Async Questions? tirsen@google.com Twitter: @tirsen
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