Github user bbende commented on the issue:
https://github.com/apache/nifi/pull/1879
Reviewing... there are two places in HortonworksSchemaRegistry where
client.getSchemaVersionInfo is called without attempting to use the cache
stored in the controller service and ends up failing if the schema registry is
down, even though the SchemaVersionInfo should be in the local cache:
```
ExecutionException: javax.ws.rs.ProcessingException:
java.net.ConnectException: Connection refused
java.lang.RuntimeException:
com.google.common.util.concurrent.UncheckedExecutionException:
javax.ws.rs.ProcessingException: java.net.ConnectException: Connection refused
at
com.hortonworks.registries.schemaregistry.client.SchemaRegistryClient.getSchemaVersionInfo(SchemaRegistryClient.java:470)
at
org.apache.nifi.schemaregistry.hortonworks.HortonworksSchemaRegistry.retrieveSchema(HortonworksSchemaRegistry.java:271)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at
org.apache.nifi.controller.service.StandardControllerServiceInvocationHandler.invoke(StandardControllerServiceInvocationHandler.java:89)
at com.sun.proxy.$Proxy76.retrieveSchema(Unknown Source)
at
org.apache.nifi.schema.access.HortonworksEncodedSchemaReferenceStrategy.getSchema(HortonworksEncodedSchemaReferenceStrategy.java:69)
at
org.apache.nifi.serialization.SchemaRegistryService.getSchema(SchemaRegistryService.java:112)
```
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