Spring Integration Metadatastore - spring-integration

Question

I have added a bean called metadataStore to my spring boot + spring integration application and expected that the ftp synchronization would have been persisted and intact even after a server restart.
Nevertheless, my early tests suggests otherwise; If I start the server and let it pick-up and process 3 tests files and then restart the server, then these same 3 files will be pick-up and processed again - as if no persistent metadataStore was defined at all.
I wonder if I am missing some configuration details when setting up the datastore...
#Configuration
public class MetadataStoreConfiguration {
#Bean
public PropertiesPersistingMetadataStore metadataStore() {
PropertiesPersistingMetadataStore metadataStore = new PropertiesPersistingMetadataStore();
return metadataStore;
}
}
Also, I see in the spring-integration reference manual a short example on how to setup an idempotent receiver and metadata store. Is this what my implementation is lacking?
If that's it and if I have to set this up like in the example, where would I define my metadataStore.get and metadataStore.put calls? the outbound adapter I am using doesn't provide me with an expression attribute... Here is my naive and incomplete attempt at this:
<int-file:inbound-channel-adapter id="inboundLogFile"
auto-create-directory="true"
directory="${sftp.local.dir}"
channel="fileInboundChannel"
prevent-duplicates="true">
<int:poller fixed-rate="${setup.inbound.poller.rate}"/>
</int-file:inbound-channel-adapter>
<int:filter id="fileFilter" input-channel="fileInboundChannel"
output-channel="idempotentServiceChannel"
discard-channel="fileDiscardChannel"
expression="#metadataStore.get(payload.name) == null"/>
This is the outbound adapter used in the example:
<int:outbound-channel-adapter channel="idempotentServiceChannel" expression="#metadataStore.put(payload.name, '')"/>
In my ftp outbound adapter I can't insert the above expression :(
<int-ftp:outbound-channel-adapter id="sdkOutboundFtp"
channel="idempotentServiceChannel"
session-factory="ftpsCachingSessionFactory"
charset="UTF-8"
auto-create-directory="true"
use-temporary-file-name="false"
remote-file-separator="/"
remote-directory-expression="${egnyte.remote.dir}"
* NO EXPRESSION POSSIBLE HERE *
mode="REPLACE">
</int-ftp:outbound-channel-adapter>

Answer 1

By default, the PropertiesPersistingMetadataStore only persists the state on a normal application shutdown; it's kept in memory until then.
In 4.1.2, we changed it to implement Flushable so users can flush the state at any time.
Consider using an FileSystemPersistentAcceptOnceFileListFilter in the local-filter on the inbound adapter instead of a separate filter element. See the documentation for more information.
Starting with version 4.1.5 this filter has an option flushOnUpdate to flush() the metadata store on every update.
Other metadata stores that use an external server (Redis, Mongo, Gemfire) don't need to be flushed.