Creating a Node

Use CreateAsync/Create methods to create a node. If such node already exists, request will fail with status NodeAlreadyExists. There is no way to change this behaviour if one would want to ensure that node has specific data.

A node can be of one of the following types:

• Persistent

• Ephemeral

• PersistentSequential

• EphemeralSequential

var request = new CreateRequest("/node/path", CreateMode.EphemeralSequential)
{
    Data = new byte[73],
    CreateParentsIfNeeded = false,
};

var createResult = await client.CreateAsync(request);

Persistent vs Ephemeral Nodes

Persistent nodes exist until deleted by a deliberate request, whilst ephemeral are sustained as long as client session is alive. In more detail the difference between persistent and ephemeral nodes was discussed in overview.

Sequential Nodes

When sequential node is being created, a monotonically increasing number is being added to its path. So, the real path of created node differs from one specified in the request and is stored in NewPath property of the result:

var createResult = await client.CreateAsync("/parent/seq-child", CreateMode.EphemeralSequential);
createResult.EnsureSuccess();

Console.WriteLine(createResult.NewPath);

var createResult2 = await client.CreateAsync("/parent/seq-child", CreateMode.EphemeralSequential);
createResult2.EnsureSuccess();

Console.WriteLine(createResult2.NewPath);

// Prints:
// /parent/seq-child0000000000
// /parent/seq-child0000000001

Creation of a sequential node is handled by ZooKeeper itself and is guaranteed to be atomic. The counting is being done on the parent node and the number increases every time a node of any type (not just sequential) is created.

Creating a Node With Data

To set an arbitrary bytes as node's data, specify them in request:

var createResult = await client.CreateAsync(new CreateRequest("/path/to/node")
{
    Data = new byte[1024*1023]
);

Maximum allowed data size is 1024*1023 bytes per node. ArgumentException will be thrown if this size is exceeded.

Creating Parent Nodes

By default, client would automatically create the whole subtree if some parent nodes do not exist. To override this behaviour, set CreateParentsIfNeeded to false:

client.Create(new CreateRequest("/parent-does-not-exist/child", CreateMode.Ephemeral) { CreateParentsIfNeeded = false }).EnsureSuccess();
// Vostok.ZooKeeper.Client.Abstractions.Model.ZooKeeperException: ZooKeeper operation has failed with status 'NodeNotFound' for path '/parent-does-not-exist/child'.

Since only a persistent node can have children, all automatically created parent nodes would be persistent.