trait SynchronousWatchableZookeeper extends Zookeeper
A ZooKeeper client with synchronous and watchable operations.
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abstract
def
async: AsynchronousZookeeper
Returns a view of this client in which operations are performed asynchronously.
Returns a view of this client in which operations are performed asynchronously.
- returns
an asynchronous view of this client
- Definition Classes
- Zookeeper
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abstract
def
children(path: String): Seq[String]
Returns the children of the node specified by the given path and additionally sets a watch for any changes.
Returns the children of the node specified by the given path and additionally sets a watch for any changes.
The watch is triggered when one of the following conditions occur:
- the session state changes
- path
the path of the node
- returns
an unordered sequence containing the names of each child node
- Exceptions thrown
NoNodeExceptionif the node does not exist
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abstract
def
close(): Unit
Closes the client connection to the ZooKeeper cluster.
Closes the client connection to the ZooKeeper cluster.
A consequence of closing the connection is that ZooKeeper will expire the corresponding session, which further implies that all ephemeral nodes created by this client will be deleted.
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- Zookeeper
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abstract
def
ensure(path: String): Future[Unit]
Ensures that the value of a node, specified by the given path, is synchronized across the ZooKeeper cluster.
Ensures that the value of a node, specified by the given path, is synchronized across the ZooKeeper cluster.
An important note on consistency: ZooKeeper does not guarantee, for any given point in time, that all clients will have a consistent view of the cluster. Since reads can be served by any node in the cluster, whereas writes are serialized through the leader, there exists the possibility in which two separate clients may have inconsistent views. This scenario occurs when the leader commits a change once consensus is reached, but the change has not yet propagated across the cluster. Therefore, reads occurring before the commit has propagated will be globally inconsistent. This behavior is normally acceptable, but for some use cases, writes may need to be globally visible before subsequent reads occur.
This method is particularly useful when a write occurring in one process is followed by a read in another process. For example, consider the following sequence of operations:
- process A writes a value
- process A sends a message to process B
- process B reads the value
The assumption is that process B expects to see the value written by process A, but as mentioned, ZooKeeper does not make this guarantee. A call to this method before process B attempts to read the value ensures that all prior writes are consistently applied across the cluster, thus observing the write in process A.
- returns
a future that completes when the node is synchronized across the cluster
- Definition Classes
- Zookeeper
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abstract
def
exists(path: String): Option[Status]
Returns the status of the node specified by the given path if it exists and additionally sets a watch for any changes.
Returns the status of the node specified by the given path if it exists and additionally sets a watch for any changes.
The watch is triggered when one of the following conditions occur:
- the data associated with the node changes
- the node is created
- the node is deleted
- the session state changes
- path
the path of the node
- returns
a
Somecontaining the node status orNoneif the node does not exist
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abstract
def
get(path: String): (Array[Byte], Status)
Returns the data and status of the node specified by the given path and additionally sets a watch for any changes.
Returns the data and status of the node specified by the given path and additionally sets a watch for any changes.
The watch is triggered when one of the following conditions occur:
- the data associated with the node changes
- the node is deleted
- the session state changes
- path
the path of the node
- returns
a tuple containing the data and status of the node
- Exceptions thrown
NoNodeExceptionif the node does not exist
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abstract
def
sync: SynchronousZookeeper
Returns a view of this client in which operations are performed synchronously.
Returns a view of this client in which operations are performed synchronously.
- returns
a synchronous view of this client
- Definition Classes
- Zookeeper
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