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From Kostas Kloudas <k.klou...@data-artisans.com>
Subject Re: Issue with CEP library
Date Thu, 28 Sep 2017 15:39:43 GMT
Hi Ajay,

After reading all the data from your source, could you somehow tell your sources to send 
a watermark of Long.MaxValue (or a high value)??

I am asking this, just to see if the problem is that the data is simply buffered inside Flink
because
there is a problem with the timestamps and the watermarks.
You could also see this from the WebUi, but seeing the size of your checkpointed state.
If the size increases, it means that something is stored there.

I will also have a deeper look.

Kostas

> On Sep 28, 2017, at 5:17 PM, Ajay Krishna <ajaykrishna@gmail.com> wrote:
> 
> Hi Kostas,
> 
> Thank you for reaching out and for the suggestions. Here are the results
> 
> 1. Using an env parallelism of 1 performed similar with the additional problem that there
was significant lag in the kafka topic
> 2. I removed the additional keyBy(0) but that did not change anything
> 3. I also tried only to check for the start only pattern and it was exactly the same
where I saw one of the homes going through but 3 others just getting dropped. 
> 4. I also tried slowing down the rate from 5000/second into Kafka to about 1000/second
but I see similar results. 
> 
> I was wondering if you had any other solutions to the problem. I am specially concerned
about 1 and 3. Is this library under active development ? Is there a JIRA open on this issue
and could be open one to track this ? 
> 
> 
> I was trying read on Stackoverlfow and found a user had a very very similar issue in
Aug'16. So I also contacted him to discuss the issue and learn't that the pattern of failure
was exactly the same. 
> 
> https://stackoverflow.com/questions/38870819/flink-cep-is-not-deterministic <https://stackoverflow.com/questions/38870819/flink-cep-is-not-deterministic>
> 
> 
> Before I found the above post, I created a post for this issue
> https://stackoverflow.com/questions/46458873/flink-cep-not-recognizing-pattern <https://stackoverflow.com/questions/46458873/flink-cep-not-recognizing-pattern>
> 
> 
> 
> I would really appreciate your guidance on this. 
> 
> Best regards,
> Ajay
> 
> 
> 
> 
> 
> On Thu, Sep 28, 2017 at 1:38 AM, Kostas Kloudas <k.kloudas@data-artisans.com <mailto:k.kloudas@data-artisans.com>>
wrote:
> Hi Ajay,
> 
> I will look a bit more on the issue.
> 
> But in the meantime, could you run your job with parallelism of 1, to see if the results
are the expected?
> 
> Also could you change the pattern, for example check only for the start, to see if all
keys pass through.
> 
> As for the code, you apply keyBy(0) the cepMap stream twice, which is redundant and introduces
latency. 
> You could remove that to also see the impact.
> 
> Kostas
> 
>> On Sep 28, 2017, at 2:57 AM, Ajay Krishna <ajaykrishna@gmail.com <mailto:ajaykrishna@gmail.com>>
wrote:
>> 
>> Hi, 
>> 
>> I've been only working with flink for the past 2 weeks on a project and am trying
using the CEP library on sensor data. I am using flink version 1.3.2. Flink has a kafka source.
I am using KafkaSource9. I am running Flink on a 3 node AWS cluster with 8G of RAM running
Ubuntu 16.04. From the flink dashboard, I see that I have 2 Taskmanagers & 4 Task slots
>> 
>> What I observe is the following. The input to Kafka is a json string and when parsed
on the flink side, it looks like this
>> 
>> (101,Sun Sep 24 23:18:53 UTC 2017,complex event,High,37.75142,-122.39458,12.0,20.0)
>> I use a Tuple8 to capture the parsed data. The first field is home_id. The time characteristic
is set to EventTime and I have an AscendingTimestampExtractor using the timestamp field. I
have parallelism for the execution environment is set to 4. I have a rather simple event that
I am trying to capture
>> 
>> DataStream<Tuple8<Integer,Date,String,String,Float,Float,Float, Float>>
cepMapByHomeId = cepMap.keyBy(0);
>> 
>>             //cepMapByHomeId.print();
>> 
>>             Pattern<Tuple8<Integer,Date,String,String,Float,Float,Float,Float>,
?> cep1 =
>>                             Pattern.<Tuple8<Integer,Date,String,String,Float,Float,Float,Float>>begin("start")
>>                                             .where(new OverLowThreshold())
>>                                             .followedBy("end")
>>                                             .where(new OverHighThreshold());
>> 
>> 
>>             PatternStream<Tuple8<Integer, Date, String, String, Float, Float,
Float, Float>> patternStream = CEP.pattern(cepMapByHomeId.keyBy(0), cep1);
>> 
>> 
>>             DataStream<Tuple7<Integer, Date, Date, String, String, Float, Float>>
alerts = patternStream.select(new PackageCapturedEvents());
>> The pattern checks if the 7th field in the tuple8 goes over 12 and then over 16.
The output of the pattern is like this
>> 
>> (201,Tue Sep 26 14:56:09 UTC 2017,Tue Sep 26 15:11:59 UTC 2017,complex event,Non-event,37.75837,-122.41467)
>> On the Kafka producer side, I am trying send simulated data for around 100 homes,
so the home_id would go from 0-100 and the input is keyed by home_id. I have about 10 partitions
in kafka. The producer just loops going through a csv file with a delay of about 100 ms between
2 rows of the csv file. The data is exactly the same for all 100 of the csv files except for
home_id and the lat & long information. The timestamp is incremented by a step of 1 sec.
I start multiple processes to simulate data form different homes.
>> 
>> THE PROBLEM:
>> 
>> Flink completely misses capturing events for a large subset of the input data. I
barely see the events for about 4-5 of the home_id values. I do a print before applying the
pattern and after and I see all home_ids before and only a tiny subset after. Since the data
is exactly the same, I expect all homeid to be captured and written to my sink which is cassandra
in this case. I've looked through all available docs and examples but cannot seem to get a
fix for the problem.
>> 
>> I would really appreciate some guidance how to understand fix this.
>> 
>> 
>> 
>> Thank you,
>> 
>> Ajay
>> 
> 
> 


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