2. Caching is all about application performance optimization ,cache can
be very useful in gaining fast application performance .
Cache scope is one of the scope in mule which saves on time and
processing load by storing and reusing frequently called data in the
memory, file system or database which saves processing time and
load if it would have to be access from original source location every
time. We can put any number of message processors into a cache
scope and configure the caching strategy to store the responses (which
contain the payload of the response message) produced by the scope’s
subflow.
Even though mule has its default caching strategy its recommended
to define the global caching strategy because The default caching
strategy uses an InMemoryObject store and should only be used for
testing;
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3. When an end user of a flight booking system is looking for the flight
information between Delhi to Kolkata for a particular date, it then
goes through the processing of various steps where it connects to
multiple vendors to collect the flight details. Finally after collecting all
the details the response will be returned to the user. Same processing
steps will be executed for each incoming requests even if multiple
users are looking for the same information. Which means if we receive
100 requests for the same source and destination search for a
particular date, then all of the processing (steps) will be done 100
times.
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4. Once the application receives the search request between Delhi to
Kolkata for a particular date the response that has been returned to
the user will be stored in a cache and for all of the next searches for
the same source and destination for that particular date the result can
just be returned from the cache without executing the same steps
repititively.
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6. Mule sends a message into the cache scope and the parent flow
expects an output. The cache scope processes the message, delivers
the output to the parent flow and saves the output (i.e. caches the
response). The next time Mule sends the same kind of message into
the cache scope, the cache scope may offer a cached response rather
than invoking, again, a potentially time-consuming process.
Each item in the cache is a key/value pair where the key represents
the payload at the cache scope entry point. The value is the result at
the end of the cache scope.By default, Mule uses
SHA256KeyGenerator and a SHA256 digest to generate a key on the
payload. For the cache entry value, Mule will cache not just the
payload at the end of the cache scope, but the whole MuleEvent. The
idea behind all of this is that apart from the payload, you might need
other information such as message properties.
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7. You can use a cache scope to reduce the processing load on the Mule
instance and speed up message processing within a flow. It is
particularly effective for:
1)Processing repeated requests for the same information.
2)Processing requests for information that involve large, non-
consumable message payloads.
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8. By default, Mule stores all cached responses in an InMemoryObjectStore.
Below are the multiple ways of creating a caching strategy and define a new
object store if you want to customize the way Mule stores cached responses.
custom-object-store:Custom object stores are useful when you want to use
a custom persistence mechanism for your ObjectStore's
In-memory: This store the data inside system memory. The data stored
with In-memory is non-persistent which means in case of application
restart or crash, the data been cached will be lost.
Managed-store: This stores the data in a place defined by
ListableObjectStore. The data stored with Managed-store is persistent
which means in case of application restart or crash, the data been cached
will no be lost.
Simple-test-file-store:This stores the data in a file. The data stored with
Simple-test-file-store configuration is persistent which means in case of
application restart or crash, the data been cached will no be lost.
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10. Mule provides the InvalidatableCachingStrategy interface, which allows
you to invalidate a complete cache or a cache key without the need for
custom code or configuration.
There are two message processors for invalidating caches:
invalidate-cache - Completely invalidates a cache. Must reference an
invalidatable caching strategy.
<ee:invalidate-cache cachingStrategy-
ref="InvalidatableCachingStrategy"/>
invalidate-key - Calculates a cache key from the current event, then
searches for it in the cache and removes it if present. Must reference
an invalidatable caching strategy and, optionally, a
MuleEventKeyGenerator. If no MuleEventKeyGenerator is provided,
Mule uses the default implementation
(SHA256MuleEventKeyGenerator).
<ee:invalidate-key cachingStrategy-
ref="InvalidatableCachingStrategy" keyGenerator-
ref="MD5MuleEventKeyGenerator"/>
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11. Let’s walk through how to use Cache scope in mule application.
In this example flow "cachFlow" will be invoked through REST client .
All of the steps including message processor's in the cache scope
will be executed for the first request made for ID= 1 and response will
be returned to the user. The same will be stored in a cache which will
be used to return response hereafter for all of the subsequent requests
made for the same ID without executing the message processor in the
cache scope.
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