Hi James,
Thanks for your help. I used reverseBytes on the sequence key. hot spotting
issue is not completely gone but better than before.
Do you think it will get better with reverse bits?
I have one more question. I see few errors in logs and I am not sure where the
issue is, we are debugging the issue but just want to post the exception incase
you encountered this before.
We are trying to insert “en_US” value to a locale column, which VARCHAR data
type, and birthdate field (DATE) comes before this locale field if that helps.
Caused by: org.apache.phoenix.exception.PhoenixParserException: ERROR 604
(42P00): Syntax error. Mismatched input. Expecting "RPAREN", got "en_US" at
line 1, column 515.
at
org.apache.phoenix.exception.PhoenixParserException.newException(PhoenixParserException.java:33)
~[phoenix-4.4.0-HBase-1.1-client-minimal.jar:na]
at
org.apache.phoenix.parse.SQLParser.parseStatement(SQLParser.java:111)
~[phoenix-4.4.0-HBase-1.1-client-minimal.jar:na]
at
org.apache.phoenix.jdbc.PhoenixStatement$PhoenixStatementParser.parseStatement(PhoenixStatement.java:1097)
~[phoenix-4.4.0-HBase-1.1-client-minimal.jar:na]
at
org.apache.phoenix.jdbc.PhoenixStatement.parseStatement(PhoenixStatement.java:1178)
~[phoenix-4.4.0-HBase-1.1-client-minimal.jar:na]
at
org.apache.phoenix.jdbc.PhoenixPreparedStatement.<init>(PhoenixPreparedStatement.java:95)
~[phoenix-4.4.0-HBase-1.1-client-minimal.jar:na]
at
org.apache.phoenix.jdbc.PhoenixConnection.prepareStatement(PhoenixConnection.java:622)
~[phoenix-4.4.0-HBase-1.1-client-minimal.jar:na]
at
com.eharmony.datastore.hbase.query.executor.PhoenixHBaseQueryExecutor.save(PhoenixHBaseQueryExecutor.java:83)
~[datastore-hbase-api-0.1.9.jar:na]
... 158 common frames omitted
Caused by: org.antlr.runtime.MismatchedTokenException: null
at
org.apache.phoenix.parse.PhoenixSQLParser.recoverFromMismatchedToken(PhoenixSQLParser.java:346)
~[phoenix-4.4.0-HBase-1.1-client-minimal.jar:na]
at org.antlr.runtime.BaseRecognizer.match(BaseRecognizer.java:115)
~[phoenix-4.4.0-HBase-1.1-client-minimal.jar:na]
at
org.apache.phoenix.parse.PhoenixSQLParser.upsert_node(PhoenixSQLParser.java:4454)
~[phoenix-4.4.0-HBase-1.1-client-minimal.jar:na]
at
org.apache.phoenix.parse.PhoenixSQLParser.oneStatement(PhoenixSQLParser.java:738)
~[phoenix-4.4.0-HBase-1.1-client-minimal.jar:na]
From: James Taylor <[email protected]<mailto:[email protected]>>
Reply-To: "[email protected]<mailto:[email protected]>"
<[email protected]<mailto:[email protected]>>
Date: Tuesday, November 3, 2015 at 6:49 PM
To: user <[email protected]<mailto:[email protected]>>
Subject: Re: Help with salting
Hi Vijay,
Have you considered generating your IDs in a way that prevents hotspotting? One
way might be to reverse the bits you get back from the sequence generator. You
could write a simple UDF that does that: https://phoenix.apache.org/udf.html
See inline for answers to your questions.
Thanks,
James
On Tue, Nov 3, 2015 at 3:44 PM, Vijay Vangapandu
<[email protected]<mailto:[email protected]>> wrote:
Hi,
I integrated one of the online services in my company with hbase using apache
phoenix, after loading few millions of records I noticed that we have hotspot
problem. All the records are going to one region as the keys are generated
using sequence.
Usecase is: each user has 1000’s of records with combination of userid and
second record id as rowkey (primary key uid, XXX). When user logs in we fetch
all records by using userid and render the results to user. But updates will
always be with combination (userid + XXX). Below are my questions.
1. If I salt the table using apache phoenix, is there any performance impact
on reads as the reads has to query all regions?
Yes - for range scans, Phoenix needs to run N scans to find all the data where
N is the number of salt buckets. Worst case, that's N times more load on your
cluster, but in reality, the impact would likely be lower. A good way to think
of it is that you're loading N blocks when in the non salted case you might
only be loading 1 block.
2. If I have to salt the table, how many buckets should I use for 8 regional
servers with 272 regions, roughly 33 regions for a regions server?
Have you seen the Tuning presentation on our Presentations page?
https://phoenix.apache.org/resources.html. Maybe start with 10 or 11 salt
buckets. Looks like your region size is pretty small, so not sure how this will
impact things. Try using Pherf (https://phoenix.apache.org/pherf.html) with
different salt buckets to get an idea.
3. If I salt the table using phoenix, what is the effort to move away from
pehonix and use the hbase client directly in later times ( not that I want to
but just checking the options)
Impossible. :-) The salt byte value calculation is just a few lines of code
(see SaltingUtil.getSaltingByte()), and you'd need to run scans against all
salt buckets and merge the results. But assuming your using where clauses and
other features, that's going to be a lot of work.
Thanks for your help.
--
Vijay Vangapandu
eHarmony, Platform
Principal Software Engineer
