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Posted to users@camel.apache.org by dvlato <dv...@gmail.com> on 2017/03/24 12:02:46 UTC
Best way to poll a database and process in chunks
Hello,
I have just started working with Camel and I have what I believe is a pretty
common requirement: poll the database to fetch all the records with a
certain status, and process them in chunks (let's 10 rows at a time). I
though I could leverage the existing components to do this easily but I am
not finding the correct way:
What I have tried so far is to usa the JPA component (as we already have JPA
entities in place) to poll the database and use the @Consumed annotation to
change the status of the record (some pointers about how to deal with
transactionality are also most welcome). The problem with this approach is:
1) Here the rows are received one by one, and we can later merge them with
an aggregator, which seems suboptimal.
2) Even if we ignored the performance problem with that approach, I'm not
sure of how to configure the aggregator to have fixed size blocks but taking
into account the whole size of the batch (I mean, if after chunking we only
have 5 rows in a message, just return that instead of waiting for the 10th -
maybe it works like that by default - I don't really know).
I've seen that there is a class called "JpaPollingConsumer" which returns
all the rows instead of one by one, but I don't know if there is anyway to
use it with a "from()" clause, it seems that Camel calls "createConsumer"
and not "createPollingConsumer", right? Is there a way to use
from("jpa://...") and have Camel use the polling consumer? I have tried
using pollEnrich but in that case the @Consumed code is not executed. Is
there any other alternative?
I apologise for such basic questions, I am sure I could probably figure out
a "good enough" approach using my inexistent knowledge of Camel (we have
Camel in Action which has been great so far, but I don't see anything in
Chapter 6 regarding database polling) but, on the other hand, it's such a
common task that someone might have best practices already available. I
have browsed the myBatis and SQL docs and I think that they might be better
suited (if I am not using JPA incorrectly, which is quite likely the case),
but I will have the same problem of not knowing if I am using Camel
correctly.
--
View this message in context: http://camel.465427.n5.nabble.com/Best-way-to-poll-a-database-and-process-in-chunks-tp5796094.html
Sent from the Camel - Users mailing list archive at Nabble.com.
Re: Best way to poll a database and process in chunks
Posted by Claus Ibsen <cl...@gmail.com>.
Hi
Maybe you can try and let us see what it goes. I am not so sure we can
make this in a way to make it not complicated. How would you specify
what those IN keys are from a select statement that can return
basically anything.
On Thu, Apr 6, 2017 at 6:59 PM, dvlato <dv...@gmail.com> wrote:
> Hello Claus, Ibsen:
>
> Thank you very much for the thorough responses. We don't really need to use
> the JPA component, and I think it makes more sense to use sql/jdbc for the
> kind of bulk operations we want to do.
>
> What I think it would be really useful is to allow for the
> "onConsumeBatchComplete" SQL statement to use parameters from the select
> query. I mean, if the sql consumer is performing the query "select * from
> mytable where status=0", I would like to be able to declare the
> "onConsumeBatchComplete" query like this " update mytable set status=1 where
> idfield in (:idfield)", where the idfield parameter would be populated with
> the results of the select statement.
>
> Does my explanation make sense? I want to change the status only for the
> rows returned by the select query.
>
> Is there another way to do that currently in Camel? I tried to connect the
> output of the SQL component with another SQL component but I think I might
> need a bean processor to generate the correct body. In any case, I think
> that would be a useful built-in feature, so if you agree I will create a
> ticket for that.
>
>
>
>
>
>
>
>
>
> --
> View this message in context: http://camel.465427.n5.nabble.com/Best-way-to-poll-a-database-and-process-in-chunks-tp5796094p5797098.html
> Sent from the Camel - Users mailing list archive at Nabble.com.
--
Claus Ibsen
-----------------
http://davsclaus.com @davsclaus
Camel in Action 2: https://www.manning.com/ibsen2
Re: Best way to poll a database and process in chunks
Posted by Zoran Regvart <zo...@regvart.com>.
Hi David,
I think you will find that binding a bigger number of parameters won't
lead to better performance, both with missing statement cache due to
fluctuating number of parameters and due to not using indexes and
performing full table scans. But you should run SQL explain and gather
statistics for your own use case to see that.
I also think that you should solve this at the SQL level first. For
instance select first n rows from your table with certain status and
process those as a batch.
zoran
On Thu, Apr 6, 2017 at 6:59 PM, dvlato <dv...@gmail.com> wrote:
> Hello Claus, Ibsen:
>
> Thank you very much for the thorough responses. We don't really need to use
> the JPA component, and I think it makes more sense to use sql/jdbc for the
> kind of bulk operations we want to do.
>
> What I think it would be really useful is to allow for the
> "onConsumeBatchComplete" SQL statement to use parameters from the select
> query. I mean, if the sql consumer is performing the query "select * from
> mytable where status=0", I would like to be able to declare the
> "onConsumeBatchComplete" query like this " update mytable set status=1 where
> idfield in (:idfield)", where the idfield parameter would be populated with
> the results of the select statement.
>
> Does my explanation make sense? I want to change the status only for the
> rows returned by the select query.
>
> Is there another way to do that currently in Camel? I tried to connect the
> output of the SQL component with another SQL component but I think I might
> need a bean processor to generate the correct body. In any case, I think
> that would be a useful built-in feature, so if you agree I will create a
> ticket for that.
--
Zoran Regvart
Re: Best way to poll a database and process in chunks
Posted by dvlato <dv...@gmail.com>.
Hello Claus, Ibsen:
Thank you very much for the thorough responses. We don't really need to use
the JPA component, and I think it makes more sense to use sql/jdbc for the
kind of bulk operations we want to do.
What I think it would be really useful is to allow for the
"onConsumeBatchComplete" SQL statement to use parameters from the select
query. I mean, if the sql consumer is performing the query "select * from
mytable where status=0", I would like to be able to declare the
"onConsumeBatchComplete" query like this " update mytable set status=1 where
idfield in (:idfield)", where the idfield parameter would be populated with
the results of the select statement.
Does my explanation make sense? I want to change the status only for the
rows returned by the select query.
Is there another way to do that currently in Camel? I tried to connect the
output of the SQL component with another SQL component but I think I might
need a bean processor to generate the correct body. In any case, I think
that would be a useful built-in feature, so if you agree I will create a
ticket for that.
--
View this message in context: http://camel.465427.n5.nabble.com/Best-way-to-poll-a-database-and-process-in-chunks-tp5796094p5797098.html
Sent from the Camel - Users mailing list archive at Nabble.com.
Re: Best way to poll a database and process in chunks
Posted by "Jacobsen, Jasen W." <ja...@mitre.org>.
I didn't see the original message from dvlato.
We are doing pretty much exactly what you describe. We are using
blueprint.xml to describe our routes.
We start with a timer
<from id="_timer1" uri="timer:theTimer?period=10s&fixedRate=true"/>
Then we have some intermediate code using a bean that determines status we
are going to look for - in our case records that have changed since a
certain time.
Then we set "body" to the SQL to be executed and use the JDBC component to
execute the query - this is where things get tricky
<to id="jdbcQuery"
uri="jdbc:TheDataSource?outputType=StreamList&resetAutoCommit=false"/>
<split id="_split1" streaming="true">
<simple>${body}</simple>
<aggregate completionSize="100" completionTimeout="5000"
id="_aggregate1" strategyRef="theAggregationStrategy">
<correlationExpression>
<constant>true</constant>
<!-- aggregate all the items. -->
</correlationExpression>
<to id="_to4" uri="direct:doStuffWithBatch"/>
</aggregate>
</split>
We use outputType="StreamList" to keep from getting too many records at
one time. "resetAutoCommit=false" because of performance problems we were
seeing - it was really slow otherwise.
<split id="_split1" streaming="true"> - processes each record in the
result stream. The <simple>${body}</simple> says we want to work with the
record in the JDBC result.
Then we have an aggregator as you mentioned. The aggregator simply adds
the records to an ArrayList - it batches them.
public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
Object newBody = newExchange.getIn().getBody();
ArrayList<Object> list = null;
if (oldExchange == null) {
list = new ArrayList<Object>();
list.add(newBody);
newExchange.getIn().setBody(list);
return newExchange;
} else {
list = oldExchange.getIn().getBody(ArrayList.class);
list.add(newBody);
return oldExchange;
}
}
Finally we call the route that does whatever we want with the batch of
records.
We were doing the "split" without an aggregator, but then every record was
being processed individually and this created a lot of SQL traffic on the
insert side - i.e. It was really slow. Using the aggregator improved
performance tremendously.
I hope this helps.
- Jasen.
On 3/26/17, 3:27 AM, "Claus Ibsen" <cl...@gmail.com> wrote:
>Yeah
>
>The other sql components are likely a bit better at this, such as
>mybatis or the sql component. For the latter you can set
>useIterator=false to get the List. And you can set that
>maxMessagesPerPoll to 10 but that is after the poll, so try to set it
>on the jdbc driver, eg on template.maxRows=10 for SQL. MyBatis ought
>to have something as well to configure a max limit to the jdbc driver.
>
>The JPA component was originally not intended for arbitrary SQL and
>thus was a 1:1 jpa entity/table thingy, and it could use a bit of love
>to make the consumer to poll X together. You are welcome to log a JIRA
>
>
>On Fri, Mar 24, 2017 at 1:02 PM, dvlato <dv...@gmail.com> wrote:
>> Hello,
>> I have just started working with Camel and I have what I believe is a
>>pretty
>> common requirement: poll the database to fetch all the records with a
>> certain status, and process them in chunks (let's 10 rows at a time). I
>> though I could leverage the existing components to do this easily but I
>>am
>> not finding the correct way:
>>
>> What I have tried so far is to usa the JPA component (as we already
>>have JPA
>> entities in place) to poll the database and use the @Consumed
>>annotation to
>> change the status of the record (some pointers about how to deal with
>> transactionality are also most welcome). The problem with this
>>approach is:
>> 1) Here the rows are received one by one, and we can later merge them
>>with
>> an aggregator, which seems suboptimal.
>> 2) Even if we ignored the performance problem with that approach, I'm
>>not
>> sure of how to configure the aggregator to have fixed size blocks but
>>taking
>> into account the whole size of the batch (I mean, if after chunking we
>>only
>> have 5 rows in a message, just return that instead of waiting for the
>>10th -
>> maybe it works like that by default - I don't really know).
>>
>> I've seen that there is a class called "JpaPollingConsumer" which
>>returns
>> all the rows instead of one by one, but I don't know if there is anyway
>>to
>> use it with a "from()" clause, it seems that Camel calls
>>"createConsumer"
>> and not "createPollingConsumer", right? Is there a way to use
>> from("jpa://...") and have Camel use the polling consumer? I have tried
>> using pollEnrich but in that case the @Consumed code is not executed. Is
>> there any other alternative?
>>
>>
>> I apologise for such basic questions, I am sure I could probably
>>figure out
>> a "good enough" approach using my inexistent knowledge of Camel (we have
>> Camel in Action which has been great so far, but I don't see anything in
>> Chapter 6 regarding database polling) but, on the other hand, it's such
>>a
>> common task that someone might have best practices already available.
>>I
>> have browsed the myBatis and SQL docs and I think that they might be
>>better
>> suited (if I am not using JPA incorrectly, which is quite likely the
>>case),
>> but I will have the same problem of not knowing if I am using Camel
>> correctly.
Re: Best way to poll a database and process in chunks
Posted by Claus Ibsen <cl...@gmail.com>.
Yeah
The other sql components are likely a bit better at this, such as
mybatis or the sql component. For the latter you can set
useIterator=false to get the List. And you can set that
maxMessagesPerPoll to 10 but that is after the poll, so try to set it
on the jdbc driver, eg on template.maxRows=10 for SQL. MyBatis ought
to have something as well to configure a max limit to the jdbc driver.
The JPA component was originally not intended for arbitrary SQL and
thus was a 1:1 jpa entity/table thingy, and it could use a bit of love
to make the consumer to poll X together. You are welcome to log a JIRA
On Fri, Mar 24, 2017 at 1:02 PM, dvlato <dv...@gmail.com> wrote:
> Hello,
> I have just started working with Camel and I have what I believe is a pretty
> common requirement: poll the database to fetch all the records with a
> certain status, and process them in chunks (let's 10 rows at a time). I
> though I could leverage the existing components to do this easily but I am
> not finding the correct way:
>
> What I have tried so far is to usa the JPA component (as we already have JPA
> entities in place) to poll the database and use the @Consumed annotation to
> change the status of the record (some pointers about how to deal with
> transactionality are also most welcome). The problem with this approach is:
> 1) Here the rows are received one by one, and we can later merge them with
> an aggregator, which seems suboptimal.
> 2) Even if we ignored the performance problem with that approach, I'm not
> sure of how to configure the aggregator to have fixed size blocks but taking
> into account the whole size of the batch (I mean, if after chunking we only
> have 5 rows in a message, just return that instead of waiting for the 10th -
> maybe it works like that by default - I don't really know).
>
> I've seen that there is a class called "JpaPollingConsumer" which returns
> all the rows instead of one by one, but I don't know if there is anyway to
> use it with a "from()" clause, it seems that Camel calls "createConsumer"
> and not "createPollingConsumer", right? Is there a way to use
> from("jpa://...") and have Camel use the polling consumer? I have tried
> using pollEnrich but in that case the @Consumed code is not executed. Is
> there any other alternative?
>
>
> I apologise for such basic questions, I am sure I could probably figure out
> a "good enough" approach using my inexistent knowledge of Camel (we have
> Camel in Action which has been great so far, but I don't see anything in
> Chapter 6 regarding database polling) but, on the other hand, it's such a
> common task that someone might have best practices already available. I
> have browsed the myBatis and SQL docs and I think that they might be better
> suited (if I am not using JPA incorrectly, which is quite likely the case),
> but I will have the same problem of not knowing if I am using Camel
> correctly.
>
>
>
> --
> View this message in context: http://camel.465427.n5.nabble.com/Best-way-to-poll-a-database-and-process-in-chunks-tp5796094.html
> Sent from the Camel - Users mailing list archive at Nabble.com.
--
Claus Ibsen
-----------------
http://davsclaus.com @davsclaus
Camel in Action 2: https://www.manning.com/ibsen2