Hi All,I am sorry for double posting and for posting a use related e-mail in
dev forum. Doing this because, I got no response to some of e-mails in the
users' list.
I have two main problems:
1. The aggregator functionality is not behaving as it should. I need to
understand how aggregators work in Giraph to resolve that problem. So my
questions are:
a. I observed that more than one objects of my custom aggregator class get
instantiated per worker, why so?b. I also observed that there is a master
aggregator which seems to be getting the locally aggregated values from various
workers. When this master-aggregator receives a value from one of the
local-aggregators, it forgets the previously aggregated value, which should not
happen. I have posted code-snippet and log messages in the users' forum also
given in the attached e-mail.c. Is this a bug in Giraph?d. How can I
understand Aggregator behaviour of Giraph in detailed, is reading the
source-code of Giraph the only option?e. Is something wrong in what I am
doing?
2. Sometimes the Giraph jobs hang, and I noticed that I get similar problems
as mentioned in Jira issue - GIRAPH-806. I observed that there is a patch
available for this issue. But when I try to apply the patch on top of Giraph
1.0.0, I face the problem that the patch has been provided on a nightly build
dated ---> 1390205044000 ( I did not understand this date format), and not on
Giraph 1.0.0.
a. Should I upgrade to 1.1.0 ( when it becomes available)?b. I upgrade to
nightly build of 1390205044000, and then apply this patch?c. What is the
suggested way out for me now?
Seeking your opinion on the above mentioned issues. I heavily rely on Giraph
for my work, and I am completely stuck because of the above mentioned issues.
Rquesting you to help me in this regard.
-Puneet
On Monday, November 17, 2014 8:58 AM, Puneet Agarwal
<[email protected]> wrote:
I have no clue on how to resolve this issue. Any guidance in this situation
can be helpful.
Claudio - is there any detailed description of how aggregator works in Giraph
in your book?
Getting no response from anyone, should such questions be asked in developers'
list?
-PuneetIIT Delhi, India
On Sunday, November 16, 2014 12:11 PM, Puneet Agarwal
<[email protected]> wrote:
Hi All,
I have been facing a problem in Giraph for last two weeks. Following is the
detailed description, sample code, corresponding log message and a few
questions.
I will greatly appreciate any help in this regard.
Code Description:
=================
My algorithm assigns a score to select vertexes of the graph. I have to find
the best K(=5) vertexes such that their score is minimum.
I have written a Persistent Aggregator for this which takes Text value. The
snippet of the code is given below.
It works fine on my laptop (single worker), but not on the cluster of 4
computers, when running with 10 workers.
I am using Hadoop 1.0.0 and Giraph 1.0.0.
Problem Description:
====================
In the aggregator one of the previously aggregated value suddenly gets lost.
Therefore, my algorithm generates wrong results.
You can observe this in the logs, given below, in following manner
a. At line number 11, the vertex 8.4793-1 has weight 3.0, and it is the best
so far.
b. At line number 12, the aggregator receives a new value "6.1100-1,6.0",
i.e., vertex=6.1100-1 has weight=6.0
c. At line number 13, in the begining of aggregate method, the output of
getAggregatedValue() is also same as newValue.
This means it simply forgets the previously aggregated value, why so?
I have printed object-ids also, in the log messages, in order to ensure that
this is happening in the same object.
Source Code Snippet:
====================
@Override
public void aggregate(Text value) {
printLogMessage("aggregate", "MyAGG", "Entering - NewValue=", value);
printLogMessage("aggregate", "MyAGG",
"Entering - getAggregatedValue()=", getAggregatedValue());
// Main Logic is here - Omitting for simplicity
setAggregatedValue(new Text(myTopK));
printLogMessage("aggregate", "MyAGG", "Exiting AggregatedValue=",
getAggregatedValue().toString());
}
@Override
public Text createInitialValue() {
printLogMessage("=====>createInitialValue", "MyAGG",
"Entering getAggregatedValue()=", getAggregatedValue());
Text initialValue = getAggregatedValue();
if (initialValue == null) {
initialValue = new Text();
}
printLogMessage("=====>createInitialValue", "MyAGG",
"Exiting ReturnedValue=", getAggregatedValue());
return initialValue;
}
private void printLogMessage(String methodName, String prefix, String msg,
Object obj) {
if (isDebugOn(methodName)) {
if (obj == null) {
obj = "";
}
System.out.println(java.lang.System.identityHashCode(this) + "--"+
prefix + "==>" +
methodName + "() - " + msg + obj.toString());
}
}
Printed Log Messages:
=====================
1. %%%%%%%%%%%%% Entered Master Compute %%%%%%%%%%%%%%%%%%%% ====> SupsetStep
No.=2
2. 249768912--MyAGG==>=====>createInitialValue() - Entering
getAggregatedValue()=
3. 249768912--MyAGG==>=====>createInitialValue() - Exiting ReturnedValue=
4. 249768912--MyAGG==>aggregate() - Entering - NewValue=8.4793-1,3.0
5. 249768912--MyAGG==>aggregate() - Entering -
getAggregatedValue()=8.4793-1,3.0
6. 249768912--MyAGG==>aggregate() - Received AggregatedValue Again- Exiting
CurrVal=8.4793-1,3.0
7. 249768912--MyAGG==>=====>createInitialValue() - Entering
getAggregatedValue()=8.4793-1,3.0
8. 249768912--MyAGG==>=====>createInitialValue() - Exiting
ReturnedValue=8.4793-1,3.0
9. %%%%%%%%%%%%% Entered Master Compute %%%%%%%%%%%%%%%%%%%% ====> SupsetStep
No.=3
10. 249768912--MyAGG==>=====>createInitialValue() - Entering
getAggregatedValue()=8.4793-1,3.0
11. 249768912--MyAGG==>=====>createInitialValue() - Exiting
ReturnedValue=8.4793-1,3.0
12. 249768912--MyAGG==>aggregate() - Entering - NewValue=6.1100-1,6.0
13. 249768912--MyAGG==>aggregate() - Entering -
getAggregatedValue()=6.1100-1,6.0
14. 249768912--MyAGG==>aggregate() - Received AggregatedValue Again- Exiting
CurrVal=6.1100-1,6.0
15. 249768912--MyAGG==>=====>createInitialValue() - Entering
getAggregatedValue()=6.1100-1,6.0
16. 249768912--MyAGG==>=====>createInitialValue() - Exiting
ReturnedValue=6.1100-1,6.0
17. %%%%%%%%%%%%% Entered Master Compute %%%%%%%%%%%%%%%%%%%% ====> SupsetStep
No.=4
18. ...
...
My Queries:
===========
1. Why does the createInitialValue method gets called twice, in the same
superstep, on the same object of the aggregator?
2. Even if its gets called twice, why should it forget the previouly
aggregated value?
Please help me resolve this issue. This is a major problem in my work.
I am not able to proceed further because of this.
Thanks in anticipation.
- Puneet
IIT Delhi, India
