How should I partition data in s3 for use with hadoop hive?

Question

I have a s3 bucket containing about 300gb of log files in no particular order.

I want to partition this data for use in hadoop-hive using a date-time stamp so that log-lines related to a particular day are clumped together in the same s3 'folder'. For example log entries for January 1st would be in files matching the following naming:

s3://bucket1/partitions/created_date=2010-01-01/file1
s3://bucket1/partitions/created_date=2010-01-01/file2
s3://bucket1/partitions/created_date=2010-01-01/file3

etc

What would be the best way for me to transform the data? Am I best just running a single script that reads in each file at a time and outputs data to the right s3 location?

I'm sure there's a good way to do this using hadoop, could someone tell me what that is?

What I've tried:

I tried using hadoop-streaming by passing in a mapper that collected all log entries for each date then wrote those directly to S3, returning nothing for the reducer, but that seemed to create duplicates. (using the above example, I ended up with 2.5 million entries for Jan 1st instead of 1.4million)

Does anyone have any ideas how best to approach this?

Answer 1

Why not create an external table over this data, then use hive to create the new table?

create table partitioned (some_field string, timestamp string, created_date date) partition(created_date);
insert overwrite partitioned partition(created_date) as select some_field, timestamp, date(timestamp) from orig_external_table;

In fact, I haven't looked up the syntax, so you may need to correct it with reference to https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DML#LanguageManualDML-InsertingdataintoHiveTablesfromqueries .

Answer 2

If Hadoop has free slots in the task tracker, it will run multiple copies of the same task. If your output format doesn't properly ignore the resulting duplicate output keys and values (which is possibly the case for S3; I've never used it), you should turn off speculative execution. If your job is map-only, set mapred.map.tasks.speculative.execution to false. If you have a reducer, set mapred.reduce.tasks.speculative.execution to false. Check out Hadoop: The Definitive Guide for more information.