NiFi Remove duplicates Error

[#1]

I encountered the following run-time error using NiFi at a Remove-duplicates processor.

Can anybody tell what's wrong and the possible causes for this?

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18:05:37 ESt - hostname:9090 - ERROR

DetectDuplicate[id=2345438...534213134] Unable to communicate with cache when processing

StandardFlowFileRecord[uuid=ae375a5a...40fdf9, claim=StandardContentClaim

[resourceClaim=StandardResourceClaim[id=1498208137037-7, container=default, sectin=7, offset=116400, length=26691],

offset=25782,name=SeedURL,size=247]

due to java.net.ConnectException: Connection was refused

java.net.ConnectException: Connection was refused

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[#2]

@Yu Song

It looks like the processor couldn't communicate with the Distribute Cache Service controller service it uses for detecting duplicates.

Does this error occur often?

[#3]

Did you configure a DistributedMapCacheClient but not a DistributedMapCacheServer for it to connect to?

[#4]

@Wynner

it doesn't happen right away but once it occurs the error stays there for a few moments.

we can just ignore it and let it go?