-UDF Performance Problem
James Newhaven 2012-09-03, 16:32
I'd appreciate if anyone has some ideas/pointers regarding a pig script and
custom UDF I have written. I've found it runs too slowly on my hadoop
cluster to be useful.......
I have two million records inside a single 600MB file.
For each record, I need to query a web service to retrieve additional data
for this record.
The web service supports batch requests of up to 50 records.
I split the two million records into bags of 50 items (using the datafu
BagSplit UDF) and then pass each bag on to a custom UDF I have written that
processes each bag and queries the web service.
I noticed when my script reaches my UDF, only one reducer is used and the
job takes forever to complete (in fact it has never finished since I
terminate it after a few hours).
My script looks like this:
A = LOAD 'records.txt' USING PigStorage('\t') AS (recordId:int);
B = GROUP B ALL;
SPLITS = FOREACH B GENERATE Flatten(BagSplit(50,A));
COMPLETE_RCORDS = FOREACH SPLITS GENERATE FLATTEN(MyCustomUDF($0));