SchemaPresenceChecker (venice API)

java.lang.Object
- com.linkedin.venice.serialization.avro.SchemaPresenceChecker

```
public class SchemaPresenceChecker
extends java.lang.Object
```
This class helps checks presence of a schema version in ZK. This can be used to ensure forward compatibility when a protocol gets upgraded.

Constructor Summary

Constructors
Constructor Description

SchemaPresenceChecker(SchemaReader schemaReader, AvroProtocolDefinition avroProtocolDefinition)

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`verifySchemaVersionPresentOrExit()`
`void`	`verifySchemaVersionPresentOrExit(java.util.Optional<java.lang.Integer> protocolVersion, boolean retry)`	When schema is present this returns nothing, otherwise it throws an exception and exits the JVM.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - SchemaPresenceChecker
```
public SchemaPresenceChecker(SchemaReader schemaReader,
                             AvroProtocolDefinition avroProtocolDefinition)
```
- Method Detail
  - verifySchemaVersionPresentOrExit
```
public void verifySchemaVersionPresentOrExit(java.util.Optional<java.lang.Integer> protocolVersion,
                                             boolean retry)
```
    When schema is present this returns nothing, otherwise it throws an exception and exits the JVM. This is added for testing purpose.
    
    Parameters:
    
    protocolVersion - -- the protocol version to fetch the schema for, if not present then fetch the current version.
    
    retry - -- should retry fetching the schema or not
  - verifySchemaVersionPresentOrExit
```
public void verifySchemaVersionPresentOrExit()
```