Hadoop - Performance Tuning
A Hadoop job is slow because reducers are waiting too long for map outputs. What tuning can reduce this delay?
A Hadoop job is slow because reducers are waiting too long for map outputs. What tuning can reduce this delay?
medium📝 Debug Q7 of 15
Step-by-Step Solution
Solution:
Step 1: Identify cause of reducer waiting
Reducers wait for all map tasks to finish and shuffle data before starting.Step 2: Tune map task memory to speed map completion
Increasing map memory helps map tasks finish faster, reducing reducer wait time.Final Answer:
Increase map task memory to speed up map completion -> Option BQuick Check:
Map memory up = Less reducer wait [OK]
Quick Trick: Boost map memory to reduce reducer wait time [OK]
Common Mistakes:
- Increasing reducers doesn't reduce map wait
- Decreasing mappers may slow job
- Disabling speculative execution unrelated here
Master "Performance Tuning" in Hadoop
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