@theotherwillembotha/node-red-zookeeper

Apache ZooKeeper integration nodes for Node-RED. Built on @theotherwillembotha/node-red-plugincore.

Nodes

| Node | Description | |------|-------------| | Zookeeper Server | Config node - defines a connection to a ZooKeeper ensemble. Shared across all ZooKeeper nodes in the flow. | | Zookeeper Event | Subscribes to a ZooKeeper node path and emits a message each time the value changes. | | Zookeeper Read | Reads the current value of a ZooKeeper node on demand when a message arrives. | | Zookeeper Write | Writes data to a ZooKeeper node when a message arrives. Creates intermediate paths automatically. |

Installation

Either use the Manage Palette option in the Node-RED editor, or run the following command in your Node-RED user directory (typically ~/.node-red):

npm install @theotherwillembotha/node-red-zookeeper

[!IMPORTANT] This plugin requires @theotherwillembotha/node-red-plugincore to be installed.

node-red-plugincore is declared as a dependency and npm will install it automatically alongside this package. However, due to a known Node-RED limitation, packages that arrive as transitive npm dependencies are only discovered by the Node-RED runtime on the next startup.

You have two options:

• Install @theotherwillembotha/node-red-plugincore via the palette manager or npm install first, then install this plugin - both will be available immediately without a restart.
• Install this plugin directly - node-red-plugincore will be installed automatically alongside it. Restart Node-RED once and both packages will be fully loaded.

Node Details

Zookeeper Server (Config Node)

Connects to a ZooKeeper ensemble and manages the underlying client lifecycle. All ZooKeeper flow nodes reference a single config node, so only one connection is maintained per ensemble.

| Field | Description | |-------|-------------| | Name | Display label for this config node | | Servers | Comma-separated list of ZooKeeper server addresses (e.g. zookeeper:2181 or host1:2181,host2:2181) | | Username | Optional authentication username | | Password | Optional authentication password | | Cache Timeout | Optional cache timeout value |

Use the Test Connection button to verify connectivity before saving. The result is shown inline without saving the node.

Zookeeper Event Node

Subscribes to a ZooKeeper node path and emits a message each time the value at that path changes.

| Field | Description | |-------|-------------| | Name | Display label for this node | | Server | The Zookeeper Server config node to use | | Subscription | The ZooKeeper node path to watch (e.g. /my/service/config) | | Get Value on Subscribe | If enabled, immediately reads and emits the current value when the subscription is first established - including on flow deployment |

Output:

| Property | Value | |----------|-------| | msg.topic | The ZooKeeper path that changed | | msg.payload | The new value - parsed as JSON if possible, otherwise a plain string |

The node status indicator shows Connected (green dot) or Disconnected (red dot) in real time. If the subscribed path does not yet exist, the node waits and begins watching as soon as it is created.

Zookeeper Read Node

Reads the current value of a ZooKeeper node whenever a message is received.

| Field | Description | |-------|-------------| | Name | Display label for this node | | Server | The Zookeeper Server config node to use | | Node Path | The ZooKeeper path to read. Supports msg, flow, global, and str (literal) types | | Output Path | Where to write the result in the output message. Supports msg, flow, and global types |

The input message passes through unchanged except for the value written at Output Path. The value is parsed as JSON if possible; otherwise written as a plain string.

Node Path examples:

| Type | Value | Resolves to | |------|-------|-------------| | str | /services/config | literal path /services/config | | msg | topic | value of msg.topic at runtime | | flow | zkpath | value of the zkpath flow context variable |

Zookeeper Write Node

Writes data to a ZooKeeper node whenever a message is received. Intermediate paths are created automatically as persistent nodes if they do not already exist.

| Field | Description | |-------|-------------| | Name | Display label for this node | | Server | The Zookeeper Server config node to use | | Node Path | The ZooKeeper path to write to. Supports msg, flow, global, and str (literal) types | | Template | A Handlebars template for the data to write. The incoming message is available as msg |

The input message passes through unchanged on successful write.

Template examples:

| Template | Description | |----------|-------------| | {{{json msg.payload}}} | Serialise the full payload as a JSON string | | {{msg.payload.value}} | Write a single field as a plain string | | {"ts":"{{msg._msgid}}"} | Construct a JSON string inline |

Example Flow

The three flow nodes in action - an event listener, a write trigger, and a read trigger, all connected to the same ZooKeeper server config node:

Prerequisites

• Node.js 18+
• Node-RED 3+
• A running Apache ZooKeeper instance or ensemble reachable from your Node-RED host

Repository

• Source: github.com/theotherwillembotha/nodered_zookeeper
• Issues: github.com/theotherwillembotha/nodered_zookeeper/issues

License

ISC