Cache mediator in WSO2 ESB
used when we see same type of message again and again and also process with
same output. In this scenario if we want to optimize our ESB performance, we
can use cache mediator. Cache mediator checks if the same type of message has
been processed before, it cashes the message and on the same request mediator
gets the message from the cache and reply back.
Cache mediator uses the
hashes for checking the equivalence the message. In cache mediator you can
define the cache response time and message size in bytes.
Test
Case:
In our test case, we will
use same service I have created in my last blog. Basically it is a data service
and we have created a pass through proxy of this DSS service in ESB. This
service gives the employee details based on the Employee Id.
We will try to cache the
DSS response in ESB so that on same request of ESB does not hit the DSS server
and reply the cached response to the client.
To understand whether
cache is working fine or not, I will change the employee details in Database
but change should not reflect in our response till message is cached. We are
assuming that ESB cache Mediator will not hit the DSS and it will give response
from the cached message.
Below is the DSS service I have created in my last blog.
Below is the ESB service,
pass through proxy of DSS.
Service gives the details
of employee based on the Employee Id. Below is the SOAP UI request and response
of ESB pass through proxy.
You can add Cache mediator
in Advance group.
Below are the fields you
need to fill to use Cache mediator.
- Cache Id: This is the cache id for the configuration.
- Cache Scope: It is important when you are using cluster.
- Per Host: It Cache the message for the current host of the cluster.
- Per-Mediator: It Cache the message once for the whole cluster.
- Cache Type: It is used to check the message is coming from the request or we need to cache the response for outgoing message.
- Finder: When message needs to be cached from incoming path, it hash the each incoming message.
- Collector: It indicates the message needs to be collected from cached message. It is used for outgoing path.
- Hash Generator: It is by default selected to org.wso2.caching.digest.DOMHASHGenerator and it has the hash logic to check each incoming message.
- Cache Timeout: We need to specify the timeout in seconds that how much we want to cache the message.
- Maximum Message Size: The limit of cache message in bytes.
Cache Implementation Details
- Implementation Type: Default to set “In-Memory” and this is the only available.
- Maximum Size: 1000 is default selected.
On Cache Hit: It basically tells that which sequence needs to be followed from registry.
Now edit the out sequence
as defined below.
Specify the Cache id, cache Scope and Cache
Type. In out sequence we are using “Collector” Cache type because we need to
get the response from cache in out going message.
Now we check that what is there in our database.
You can see that for Employee Id 1,
we have Employee Name as ‘Shri’ and
address is ‘Delhi’ as highlighted in
Yellow.
Let see what we are
getting in SOAP UI response.
Same thing we are getting
in response and in one hit the response is cached.
Now
I am going to change the address from “Delhi”
to “Noida” as below.
Now if you try within 20
second, this is what we have mentioned in our cache response. We should be
getting same response.
And Yes, as above we are
getting the same response because response is cached we it is not coming from
DSS server. If we hit just after 20 second we can see the address is now
updated from “Delhi” to “Noida”.
Now this response will be
cached till net 20 second in each hit.
You can see that from the
IN sequence we are getting the response.
ESB
Synapse Code:
<proxy
name="DSS_EmployeeDetailDataServiceProxy" transports="http"
startOnLoad="true" trace="disable"
statistics="enable">
<target
inSequence="DSS_EmployeeDetailDataService_IN"
outSequence="CommonSequence_OUT" faultSequence="DSS_EmployeeDetailDataService_Fault"/>
<publishWSDL
key="DSS_EmployeeDetailDataService_wsdl"/>
</proxy>
<localEntry
key="DSS_EmployeeDetailDataService_wsdl"
src="file:repository/conf/employee/EmployeeDetailDataService.wsdl"/>
<sequence name="DSS_EmployeeDetailDataService_Fault">
<log level="full"/>
<payloadFactory>
<format>
<shr:employees
xmlns:shr="http://shriwithjava.blogspot.co.nz/">
<shr:employee>
<shr:id>Exception
has been caught</shr:id>
<shr:name>Exception has been caught</shr:name>
<shr:address>Exception has been caught</shr:address>
</shr:employee>
</shr:employees>
</format>
</payloadFactory>
<property name="RESPONSE"
value="true"/>
<header name="To"
action="remove"/>
<send/>
<drop/>
</sequence>
<sequence
name="DSS_EmployeeDetailDataService_IN">
<log level="full"/>
<cache id="GetEmpDetailCache"
scope="per-host" collector="false"
hashGenerator="org.wso2.caching.digest.DOMHASHGenerator"
timeout="20" maxMessageSize="500">
<implementation type="memory" maxSize="1000"/>
</cache>
<send>
<endpoint
key="DSS_EmployeeDetailDataService_EPR"/>
</send>
</sequence>
<sequence
name="CommonSequence_OUT">
<log level="full"/>
<cache id="GetEmpDetailCache"
scope="per-host" collector="true"/>
<send/>
</sequence>
<endpoint
name="DSS_EmployeeDetailDataService_EPR">
<address
uri="http://10.251.162.192:9763/services/EmployeeDataService">
<timeout>
<duration>10000</duration>
<responseAction>fault</responseAction>
</timeout>
<suspendOnFailure>
<errorCodes>101500,101501,101506,101507,101508</errorCodes>
<initialDuration>3000</initialDuration>
<progressionFactor>1.0</progressionFactor>
</suspendOnFailure>
<markForSuspension>
<errorCodes>101504,101505</errorCodes>
<retriesBeforeSuspension>3</retriesBeforeSuspension>
<retryDelay>1</retryDelay>
</markForSuspension>
</address>
</endpoint>
