Hi Mario,
you could use jms to achieve async behaviour and serialization.
My design would look like this:
- one topic for the queries
- the web application sends the query to the topic
- you have one listener for each data source
- You can limit the number of consumer threads to 1 and also the number
of threads for the executor thread pool to 1 to make sure each source
only processes one message at a time
- after the query you send the result back to a common response queue
- the web appplication listens on the response queue and prints each
response
- to differentiate between the queries each query should have a query id
and the response should also contain the query id
So the routes could look like this:
For each search source you have:
from("jms:topic:mytopic").bean(new MysearchBean1()).to("jms:myreplyqueue");
class MySearchBean1() {
public Result search(Query query) {
...
}
}
Query and Result should be jaxb annotated classes. So if you have
camel-jaxb on the path camel converts from jms messages to the objects
automatically. (See also
http://www.liquid-reality.de/display/liquid/2011/10/19/Using+Camel+to+do+light+weight+messaging+over+any+protocol
)
In the web application you use a producerTemplate to send the query:
context.createProducerTemplate().sendBody("jms:topic:mytopic", query);
Alternatively you can use the aproach described in my blog article to
hide that behind a java interface.
A route in the web application receives the result:
from("jms:myreplyqueue").bean(new MyResponseHandler());
class MyresponseHandler {
public void handle(Response response);
}
So this class should figure out to which query the response belongs to
and display it in the correct session.
One problem with this aproch is that you do not know exactly when all
responses are there. As long as the number of engines is fixed you can
count the responses though.
Some advantages of this design are:
- You can easily add more engines and deploy them on the same or
different machines
- You can add more search sources on the fly
- Your java code will contain no references to camel so it is easy to
unit test independently from camel
Christian
Am 09.12.2011 23:56, schrieb mgiammarco:
Hello,
I would like to use camel to realize this (apparently) simple web
application:
- a CONCURRENT MULTIUSER web application with a simple search page like
google;
- results MUST appears asynchronously as soon as they can;
- I need to query several databases (SQL,HTTP,WEBSERVICES,TELNET)
concurrently;
- The query in one database MUST be serialized.
I am worried regarding last point because obviously tomcat for each user
will create a new session and I do not know if camel can create a
"singleton" queue to serialize access to the db.
Thank you in advance for any help!
Mario
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Christian Schneider
http://www.liquid-reality.de
Open Source Architect
Talend Application Integration Division http://www.talend.com
