Hadoop - Performance Tuning
In Hadoop's Java API, which method correctly sets the number of reduce tasks for a job?
In Hadoop's Java API, which method correctly sets the number of reduce tasks for a job?
easy📝 Syntax Q3 of 15
Step-by-Step Solution
Solution:
Step 1: Identify the correct method
The Hadoop Job class provides a direct method setNumReduceTasks(int) to set the number of reducers.Step 2: Analyze other options
job.getConfiguration().setNumReduceTasks(5); is incorrect because Configuration does not have setNumReduceTasks method. job.setReducerCount(5); is invalid as setReducerCount does not exist. job.getConfiguration().setInt("mapreduce.job.reduces", 5); sets the configuration property but not via the recommended API method.Final Answer:
job.setNumReduceTasks(5); -> Option BQuick Check:
Use Job's setNumReduceTasks method [OK]
Quick Trick: Use job.setNumReduceTasks() to set reducers [OK]
Common Mistakes:
- Trying to set reducers via Configuration directly
- Using non-existent methods like setReducerCount
- Confusing map task settings with reduce tasks
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