InodeLockList (Alluxio Parent 2.2.3-SNAPSHOT API)

All Superinterfaces:

AutoCloseable

All Known Implementing Classes:

CompositeInodeLockList, SimpleInodeLockList
```
@NotThreadSafe
public interface InodeLockList
extends AutoCloseable
```
Represents a locked path within the inode tree. Both inodes and edges are locked along the path. The path may start from either an edge or an inode. A lock list always contains some number of read locks (possibly zero) followed by some number of write locks (possibly zero). This class uses list notation to describe lock lists. Nodes are single letters, edges are parentName->childName, and write-locks are indicated with '*'. For example, a lock list for /a/b/c/d where the c->d edge is the first write-locked element: [->/, /, /->a, a, a->b, b, b->c, c, c->d*, d*] The "->/" at the start is a pseudo-edge used to allow the WRITE_EDGE lock mode to be applied to the root. This edge can only be locked by calling lockRootEdge. Not all lock lists need to start from the root. Another example list could be [b, b->c, c->d*, d*] This allows us to create composite lock lists out of a "normal" lock list starting from the root, plus a non-root lock list.

Method Summary

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method and Description
`void`	`close()` Closes the lock list, releasing all locks.
`void`	`downgradeEdgeToInode(Inode inode, LockMode mode)` Downgrades from edge write-locking to inode write-locking.
`void`	`downgradeLastEdge()` Downgrades the last edge lock in the lock list from WRITE lock to READ lock.
`void`	`downgradeLastInode()` Downgrades the last inode from a write lock to a read lock.
`boolean`	`endsInInode()`
`Inode`	`get(int index)`
`InodeLockManager`	`getInodeLockManager()`
`List<Inode>`	`getLockedInodes()`
`default List<InodeView>`	`getLockedInodeViews()`
`LockMode`	`getLockMode()`
`boolean`	`isEmpty()`
`void`	`lockEdge(Inode inode, String childName, LockMode mode)` Locks an edge leading out of the last inode in the list.
`void`	`lockInode(Inode inode, LockMode mode)` Locks the given inode and adds it to the lock list.
`void`	`lockRootEdge(LockMode mode)` Locks the root edge in the specified mode.
`int`	`numInodes()`
`void`	`pushWriteLockedEdge(Inode inode, String childName)` Leapfrogs the final edge write lock forward, reducing the lock list's write-locked scope.
`void`	`unlockLastEdge()` Unlocks the last locked edge.
`void`	`unlockLastInode()` Unlocks the last locked inode.

- Method Detail
  - lockRootEdge
```
void lockRootEdge(LockMode mode)
```
    Locks the root edge in the specified mode. The lock list must be empty to call this method.
    
    Parameters:
    
    mode - the mode to lock in
  - lockInode
```
void lockInode(Inode inode,
               LockMode mode)
```
    Locks the given inode and adds it to the lock list. This method does *not* check that the inode is still a child of the previous inode, or that the inode still exists. This method should only be called when the edge leading to the inode is locked. Example Starting from [a, a->b] lockInode(b, LockMode.READ) results in [a, a->b, b] lockInode(b, LockMode.WRITE) results in [a, a->b, b*]
    
    Parameters:
    
    inode - the inode to lock
    
    mode - the mode to lock in
  - lockEdge
```
void lockEdge(Inode inode,
              String childName,
              LockMode mode)
```
    Locks an edge leading out of the last inode in the list. Example Starting from [a, a->b, b] lockEdge(b, c, LockMode.READ) results in [a, a->b, b, b->c] lockEdge(b, c, LockMode.WRITE) results in [a, a->b, b, b->c*]
    
    Parameters:
    
    inode - the parent inode of the edge
    
    childName - the child name of the edge
    
    mode - the mode to lock in
  - unlockLastInode
```
void unlockLastInode()
```
    Unlocks the last locked inode. Example Starting from [a, a->b, b] unlockLastInode() results in [a, a->b]
  - unlockLastEdge
```
void unlockLastEdge()
```
    Unlocks the last locked edge. Example Starting from [a, a->b] unlockLastEdge results in [a]
  - downgradeLastInode
```
void downgradeLastInode()
```
    Downgrades the last inode from a write lock to a read lock. The read lock is acquired before releasing the write lock. Example Starting from [a, a->b, b*] downgradeLastInode() results in [a, a->b, b] If the last inode is not the only write-locked inode, no downgrade occurs.
  - downgradeLastEdge
```
void downgradeLastEdge()
```
    Downgrades the last edge lock in the lock list from WRITE lock to READ lock. Example Starting from [a, a->b*] downgradeLastEdge() results in [a, a->b]
  - pushWriteLockedEdge
```
void pushWriteLockedEdge(Inode inode,
                         String childName)
```
    Leapfrogs the final edge write lock forward, reducing the lock list's write-locked scope. Example Starting from [a, a->b*] pushWriteLockedEdge(b, c) results in [a, a->b, b, b->c*] The read lock on a->b is acquired before releasing the write lock. This ensures that no other thread can take the write lock before the read lock is acquired. If this is a composite lock list and the final write lock is part of the base lock list, the new locks will be acquired but no downgrade will occur.
    
    Parameters:
    
    inode - the inode to add to the lock list
    
    childName - the child name for the edge to add to the lock list
  - downgradeEdgeToInode
```
void downgradeEdgeToInode(Inode inode,
                          LockMode mode)
```
    Downgrades from edge write-locking to inode write-locking. This reduces the scope of the write lock by pushing it forward one entry. Example Starting from [a, a->b*] downgradeEdgeToInode(b, LockMode.READ) results in [a, a->b, b] downgradeEdgeToInode(b, LockMode.WRITE) results in [a, a->b, b*] The read lock on a->b is acquired before releasing the write lock. This ensures that no other thread can take the write lock before the read lock is acquired.
    
    Parameters:
    
    inode - the next inode in the lock list
    
    mode - the mode to downgrade to
  - getLockMode
```
LockMode getLockMode()
```
    Returns:
    
    LockMode.WRITE if the last entry in the list is write-locked, otherwise LockMode.READ
  - getLockedInodes
```
List<Inode> getLockedInodes()
```
    Returns:
    
    a copy of all locked inodes
  - getLockedInodeViews
```
default List<InodeView> getLockedInodeViews()
```
    Returns:
    
    a copy of all locked inodes
  - get
```
Inode get(int index)
```
    Parameters:
    
    index - the index of the list
    
    Returns:
    
    the inode at the specified index
  - numInodes
```
int numInodes()
```
    Returns:
    
    the size of the list in terms of locked inodes
  - endsInInode
```
boolean endsInInode()
```
    Returns:
    
    whether this lock list ends in an inode (as opposed to an edge)
  - isEmpty
```
boolean isEmpty()
```
    Returns:
    
    true if the locklist is empty
  - getInodeLockManager
```
InodeLockManager getInodeLockManager()
```
    Returns:
    
    the inode lock manager for this lock list
  - close
```
void close()
```
    Closes the lock list, releasing all locks.
    
    Specified by:
    
    close in interface AutoCloseable

Interface InodeLockList

Method Summary

Method Detail

lockRootEdge

lockInode

lockEdge

unlockLastInode

unlockLastEdge

downgradeLastInode

downgradeLastEdge

pushWriteLockedEdge

downgradeEdgeToInode

getLockMode

getLockedInodes

getLockedInodeViews

get

numInodes

endsInInode

isEmpty

getInodeLockManager

close