EditLogInputStream (Apache Hadoop HDFS 3.4.1.0-eep-940 API)

java.lang.Object
- org.apache.hadoop.hdfs.server.namenode.EditLogInputStream

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

Direct Known Subclasses:

EditLogFileInputStream
```
@Private
@Evolving
public abstract class EditLogInputStream
extends java.lang.Object
implements java.io.Closeable
```
A generic abstract class to support reading edits log data from persistent storage. It should stream bytes from the storage exactly as they were written into the #EditLogOutputStream.

Constructor Summary

Constructors
Constructor Description

EditLogInputStream()

Constructors
Constructor	Description
`EditLogInputStream()`

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`abstract void`	`close()`	Close the stream.
`java.lang.String`	`getCurrentStreamName()`	Returns the name of the currently active underlying stream.
`abstract long`	`getFirstTxId()`
`abstract long`	`getLastTxId()`
`abstract java.lang.String`	`getName()`
`abstract long`	`getPosition()`	Get the "position" of in the stream.
`abstract int`	`getVersion(boolean verifyVersion)`	Get the layout version of the data in the stream.
`abstract boolean`	`isInProgress()`	Return true if this stream is in progress, false if it is finalized.
`abstract boolean`	`isLocalLog()`	Returns true if we are currently reading the log from a local disk or an even faster data source (e.g.
`abstract long`	`length()`	Return the size of the current edits log or -1 if unknown.
`protected abstract FSEditLogOp`	`nextOp()`	Get the next operation from the stream storage.
`protected FSEditLogOp`	`nextValidOp()`	Get the next valid operation from the stream storage.
`FSEditLogOp`	`readOp()`	Read an operation from the stream
`void`	`resync()`	Position the stream so that a valid operation can be read from it with readOp().
`protected long`	`scanNextOp()`	Go through the next operation from the stream storage.
`abstract void`	`setMaxOpSize(int maxOpSize)`	Set the maximum opcode size in bytes.
`boolean`	`skipUntil(long txid)`	Skip edit log operations up to a given transaction ID, or until the end of the edit log is reached.
`java.lang.String`	`toString()`

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

- Constructor Detail
  - EditLogInputStream
```
public EditLogInputStream()
```
- Method Detail
  - getCurrentStreamName
```
public java.lang.String getCurrentStreamName()
```
    Returns the name of the currently active underlying stream. The default implementation returns the same value as getName unless overridden by the subclass.
    
    Returns:
    
    String name of the currently active underlying stream
  - getName
```
public abstract java.lang.String getName()
```
    Returns:
    
    the name of the EditLogInputStream
  - getFirstTxId
```
public abstract long getFirstTxId()
```
    Returns:
    
    the first transaction which will be found in this stream
  - getLastTxId
```
public abstract long getLastTxId()
```
    Returns:
    
    the last transaction which will be found in this stream
  - close
```
public abstract void close()
                    throws java.io.IOException
```
    Close the stream.
    
    Specified by:
    
    close in interface java.lang.AutoCloseable
    
    Specified by:
    
    close in interface java.io.Closeable
    
    Throws:
    
    java.io.IOException - if an error occurred while closing
  - readOp
```
public FSEditLogOp readOp()
                   throws java.io.IOException
```
    Read an operation from the stream
    
    Returns:
    
    an operation from the stream or null if at end of stream
    
    Throws:
    
    java.io.IOException - if there is an error reading from the stream
  - resync
```
public void resync()
```
    Position the stream so that a valid operation can be read from it with readOp(). This method can be used to skip over corrupted sections of edit logs.
  - nextOp
```
protected abstract FSEditLogOp nextOp()
                               throws java.io.IOException
```
    Get the next operation from the stream storage.
    
    Returns:
    
    an operation from the stream or null if at end of stream
    
    Throws:
    
    java.io.IOException - if there is an error reading from the stream
  - scanNextOp
```
protected long scanNextOp()
                   throws java.io.IOException
```
    Go through the next operation from the stream storage.
    
    Returns:
    
    the txid of the next operation.
    
    Throws:
    
    java.io.IOException
  - nextValidOp
```
protected FSEditLogOp nextValidOp()
```
    Get the next valid operation from the stream storage. This is exactly like nextOp, except that we attempt to skip over damaged parts of the edit log
    
    Returns:
    
    an operation from the stream or null if at end of stream
  - skipUntil
```
public boolean skipUntil(long txid)
                  throws java.io.IOException
```
    Skip edit log operations up to a given transaction ID, or until the end of the edit log is reached. After this function returns, the next call to readOp will return either end-of-file (null) or a transaction with a txid equal to or higher than the one we asked for.
    
    Parameters:
    
    txid - The transaction ID to read up until.
    
    Returns:
    
    Returns true if we found a transaction ID greater than or equal to 'txid' in the log.
    
    Throws:
    
    java.io.IOException
  - getVersion
```
public abstract int getVersion(boolean verifyVersion)
                        throws java.io.IOException
```
    Get the layout version of the data in the stream.
    
    Returns:
    
    the layout version of the ops in the stream.
    
    Throws:
    
    java.io.IOException - if there is an error reading the version
  - getPosition
```
public abstract long getPosition()
```
    Get the "position" of in the stream. This is useful for debugging and operational purposes. Different stream types can have a different meaning for what the position is. For file streams it means the byte offset from the start of the file.
    
    Returns:
    
    the position in the stream
  - length
```
public abstract long length()
                     throws java.io.IOException
```
    Return the size of the current edits log or -1 if unknown.
    
    Returns:
    
    long size of the current edits log or -1 if unknown
    
    Throws:
    
    java.io.IOException
  - isInProgress
```
public abstract boolean isInProgress()
```
    Return true if this stream is in progress, false if it is finalized.
  - setMaxOpSize
```
public abstract void setMaxOpSize(int maxOpSize)
```
    Set the maximum opcode size in bytes.
  - isLocalLog
```
public abstract boolean isLocalLog()
```
    Returns true if we are currently reading the log from a local disk or an even faster data source (e.g. a byte buffer).
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object

Class EditLogInputStream

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

EditLogInputStream

Method Detail

getCurrentStreamName

getName

getFirstTxId

getLastTxId

close

readOp

resync

nextOp

scanNextOp

nextValidOp

skipUntil

getVersion

getPosition

length

isInProgress

setMaxOpSize

isLocalLog

toString