HollowWriteStateEngine (hollow 4.8.4 API)

java.lang.Object
- com.netflix.hollow.core.write.HollowWriteStateEngine

All Implemented Interfaces:

HollowDataset, HollowStateEngine
```
public class HollowWriteStateEngine
extends java.lang.Object
implements HollowStateEngine
```
A HollowWriteStateEngine is our main handle to a Hollow dataset as a data producer.
A dataset changes over time. A core concept in Hollow is that the timeline for a changing dataset can be broken down into discrete data states, each of which is a complete snapshot of the data at a particular point in time. Data producers handle data states with a HollowWriteStateEngine.
A HollowWriteStateEngine cycles back and forth between two-phases:
1. Adding records
2. Writing the state
During the "adding records" phase, all of the records comprising the dataset are added to the state engine. During the "writing" phase, we can write snapshot blobs to initialize and/or delta blobs to keep up-to-date consumers of the dataset.
Each cycle between the phases will produce a state. During each cycle, all of the current records in the dataset should be re-added to the write state engine.

Field Summary
- Fields inherited from interface com.netflix.hollow.core.HollowStateEngine
  HEADER_TAG_SCHEMA_CHANGE

Constructor Summary

Constructors
Constructor and Description

HollowWriteStateEngine()

HollowWriteStateEngine(HollowObjectHashCodeFinder hasher)
Deprecated.

Constructors
Constructor and Description
`HollowWriteStateEngine()`
`HollowWriteStateEngine(HollowObjectHashCodeFinder hasher)` Deprecated.

Method Summary

All Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`int`	`add(java.lang.String type, HollowWriteRecord rec)` Add a record to the state.
`void`	`addAllObjectsFromPreviousCycle()` Add all of the objects from the previous cycle, exactly as they were in the previous cycle.
`void`	`addHeaderTag(java.lang.String name, java.lang.String value)`
`void`	`addHeaderTags(java.util.Map<java.lang.String,java.lang.String> headerTags)`
`void`	`addTypeState(HollowTypeWriteState writeState)` Add a type to the dataset.
`HollowObjectHashCodeFinder`	`getHashCodeFinder()` Deprecated.
`java.lang.String`	`getHeaderTag(java.lang.String name)`
`java.util.Map<java.lang.String,java.lang.String>`	`getHeaderTags()`
`long`	`getNextStateRandomizedTag()`
`HollowSchema`	`getNonNullSchema(java.lang.String schemaName)`
`java.util.List<HollowTypeWriteState>`	`getOrderedTypeStates()`
`long`	`getPreviousStateRandomizedTag()`
`HollowSchema`	`getSchema(java.lang.String schemaName)`
`java.util.List<HollowSchema>`	`getSchemas()`
`HollowTypeWriteState`	`getTypeState(java.lang.String typeName)`
`boolean`	`hasChangedSinceLastCycle()`
`boolean`	`isRestored()`
`void`	`overrideNextStateRandomizedTag(long nextStateRandomizedTag)`
`void`	`overridePreviousStateRandomizedTag(long previousStateRandomizedTag)`
`void`	`prepareForNextCycle()` Transition from the "writing" phase of a cycle to the "adding records" phase of the next cycle.
`void`	`prepareForWrite()` Transition from the "adding records" phase of a cycle to the "writing" phase of a cycle.
`void`	`resetToLastPrepareForNextCycle()` If a state was partially constructed after the last call to prepareForNextCycle(), this call will remove all of those objects from the state engine and reset to the state it was in at the last prepareForNextCycle() call.
`void`	`restoreFrom(HollowReadStateEngine readStateEngine)` Restore from the data state contained in the provided `HollowReadStateEngine`.
`void`	`setTargetMaxTypeShardSize(long targetMaxTypeShardSize)` Setting a target max type shard size (specified in bytes) will limit the excess memory pool required to perform delta transitions.

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

Methods inherited from interface com.netflix.hollow.core.HollowDataset
hasIdenticalSchemas

- Constructor Detail
  - HollowWriteStateEngine
```
public HollowWriteStateEngine()
```
  - HollowWriteStateEngine
```
@Deprecated
public HollowWriteStateEngine(HollowObjectHashCodeFinder hasher)
```
    Deprecated.
- Method Detail
  - add
```
public int add(java.lang.String type,
               HollowWriteRecord rec)
```
    Add a record to the state.
    
    Parameters:
    
    type - the type name
    
    rec - the record
    
    Returns:
    
    the ordinal of the added record
  - addTypeState
```
public void addTypeState(HollowTypeWriteState writeState)
```
    Add a type to the dataset. Should be called during the first cycle, before writing the first state.
    
    Parameters:
    
    writeState - the write state to add
  - restoreFrom
```
public void restoreFrom(HollowReadStateEngine readStateEngine)
```
    Restore from the data state contained in the provided HollowReadStateEngine. This is used to continue a delta chain after a producer is restarted.
    Before calling this method, the data model should be pre-initialized. This can be accomplished by:
    - using the HollowWriteStateCreator
    - calling HollowObjectMapper.initializeTypeState(Class) with each of the top-level classes in the data model
    - adding the types via addTypeState(HollowTypeWriteState)
    Parameters:
    
    readStateEngine - the read state to restore from
  - prepareForWrite
```
public void prepareForWrite()
```
    Transition from the "adding records" phase of a cycle to the "writing" phase of a cycle.
  - prepareForNextCycle
```
public void prepareForNextCycle()
```
    Transition from the "writing" phase of a cycle to the "adding records" phase of the next cycle.
  - addAllObjectsFromPreviousCycle
```
public void addAllObjectsFromPreviousCycle()
```
    Add all of the objects from the previous cycle, exactly as they were in the previous cycle.
  - resetToLastPrepareForNextCycle
```
public void resetToLastPrepareForNextCycle()
```
    If a state was partially constructed after the last call to prepareForNextCycle(), this call will remove all of those objects from the state engine and reset to the state it was in at the last prepareForNextCycle() call.
    This method can be called at any time, and will leave the state engine in the same state it was in immediately after the last call to prepareForNextCycle()
  - hasChangedSinceLastCycle
```
public boolean hasChangedSinceLastCycle()
```
    Returns:
    
    whether or not there are differences between the current cycle and the previous cycle.
  - isRestored
```
public boolean isRestored()
```
  - getOrderedTypeStates
```
public java.util.List<HollowTypeWriteState> getOrderedTypeStates()
```
  - getTypeState
```
public HollowTypeWriteState getTypeState(java.lang.String typeName)
```
    Parameters:
    
    typeName - the type name
    
    Returns:
    
    the specified HollowTypeWriteState
  - getSchemas
```
public java.util.List<HollowSchema> getSchemas()
```
    Specified by:
    
    getSchemas in interface HollowDataset
    
    Specified by:
    
    getSchemas in interface HollowStateEngine
    
    Returns:
    
    the schemas for all types in this dataset.
  - getSchema
```
public HollowSchema getSchema(java.lang.String schemaName)
```
    Specified by:
    
    getSchema in interface HollowDataset
    
    Specified by:
    
    getSchema in interface HollowStateEngine
    
    Parameters:
    
    schemaName - the type name
    
    Returns:
    
    the schema for the specified type in this dataset.
  - getNonNullSchema
```
public HollowSchema getNonNullSchema(java.lang.String schemaName)
```
    Specified by:
    
    getNonNullSchema in interface HollowDataset
    
    Specified by:
    
    getNonNullSchema in interface HollowStateEngine
    
    Parameters:
    
    schemaName - the type name
    
    Returns:
    
    the schema for the specified type in this dataset.
  - getHeaderTags
```
public java.util.Map<java.lang.String,java.lang.String> getHeaderTags()
```
    Specified by:
    
    getHeaderTags in interface HollowStateEngine
  - addHeaderTag
```
public void addHeaderTag(java.lang.String name,
                         java.lang.String value)
```
  - addHeaderTags
```
public void addHeaderTags(java.util.Map<java.lang.String,java.lang.String> headerTags)
```
  - getHeaderTag
```
public java.lang.String getHeaderTag(java.lang.String name)
```
    Specified by:
    
    getHeaderTag in interface HollowStateEngine
  - getHashCodeFinder
```
@Deprecated
public HollowObjectHashCodeFinder getHashCodeFinder()
```
    Deprecated.
  - getPreviousStateRandomizedTag
```
public long getPreviousStateRandomizedTag()
```
  - overridePreviousStateRandomizedTag
```
public void overridePreviousStateRandomizedTag(long previousStateRandomizedTag)
```
  - getNextStateRandomizedTag
```
public long getNextStateRandomizedTag()
```
  - overrideNextStateRandomizedTag
```
public void overrideNextStateRandomizedTag(long nextStateRandomizedTag)
```
  - setTargetMaxTypeShardSize
```
public void setTargetMaxTypeShardSize(long targetMaxTypeShardSize)
```
    Setting a target max type shard size (specified in bytes) will limit the excess memory pool required to perform delta transitions. For use cases where all consumers are running with hollow v2.1.0 or greater, it is recommended to set this value to something reasonably small, for example 25MB. In a future release, this value will default to (25 * 1024 * 1024). It is currently set to Long.MAX_VALUE to retain backwards compatibility with pre v2.1.0 consumers.
    
    Parameters:
    
    targetMaxTypeShardSize - the target max type shard size, in bytes

Class HollowWriteStateEngine

Field Summary

Fields inherited from interface com.netflix.hollow.core.HollowStateEngine

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface com.netflix.hollow.core.HollowDataset

Constructor Detail

HollowWriteStateEngine

HollowWriteStateEngine

Method Detail

add

addTypeState

restoreFrom

prepareForWrite

prepareForNextCycle

addAllObjectsFromPreviousCycle

resetToLastPrepareForNextCycle

hasChangedSinceLastCycle

isRestored

getOrderedTypeStates

getTypeState

getSchemas

getSchema

getNonNullSchema

getHeaderTags

addHeaderTag

addHeaderTags

getHeaderTag

getHashCodeFinder

getPreviousStateRandomizedTag

overridePreviousStateRandomizedTag

getNextStateRandomizedTag

overrideNextStateRandomizedTag

setTargetMaxTypeShardSize