Registry / devops / node-red-contrib-semaphore

node-red-contrib-semaphore

library1.0.1jsnpmunverified

A Node-RED node that provides semaphore functionality to limit concurrent access to resources. Version 1.0.1 is the current stable release. The package is simple and focused, offering two nodes: 'semaphore take' and 'semaphore leave'. It queues messages on a semaphore with configurable capacity. No frequent updates; maintained for basic needs. Differentiator: native Node-RED integration for flow control and resource limiting.

devops

npm install node-red-contrib-semaphore

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · NODE-RED-CONTRIB-S

node-red-contrib-semaphore

devopsjavascriptv1.0.1

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

Node-RED node

✓ Install via npm in Node-RED directory and use nodes in flows

✗ Direct require in custom JavaScript code

Node-RED nodes are loaded by the runtime, not imported directly in scripts.

semaphore node configuration

✓ Set capacity in node properties or via msg.capacity

✗ No code import needed

Configuration is done via Node-RED UI, not via code.

Using semaphore in Node-RED function node

✓ Access context or use flow control as designed

✗ Trying to require('node-red-contrib-semaphore') in function node

Node-RED nodes cannot be imported; they are instantiated by the editor.

Install and use semaphore nodes to limit concurrent execution in Node-RED flows.

# Install in Node-RED directory cd ~/.node-red npm install node-red-contrib-semaphore # Restart Node-RED # Then in flow editor add 'semaphore take' node (configure name and capacity) # Connect to nodes that need limited concurrency # Add 'semaphore leave' node after processing to release

Debug

Known issues

gotchaDeadlock if leave node not called on error; use catch node to ensure leave is called

fix

Implement error handling with Catch node that triggers a semaphore leave

affects: all

gotchaSemaphore state is lost on Node-RED restart; semaphore capacity resets to default

fix

Design flows to be tolerant of restart or use persistent context

affects: all

gotchaMultiple take nodes can be connected to same semaphore by same name; they share capacity

fix

Ensure semaphore names are unique or intended to share

affects: all

Errors

Common errors & fixes

Error: Cannot find module 'semaphore'

Missing semaphore dependency due to incomplete npm install

fix

Run 'npm install' in Node-RED directory or install globally with --save

semaphore leave not freeing slot

Leave node not triggered; perhaps due to error in flow

fix

Add error handling with Catch node to call leave on error

Upgrade

Version history

1.0.1latest on npm

Audit

Dependencies

semaphorerequiredcore semaphore logic

Agent activity

2 hits · last 30 days

node

Resources

githubhttps://github.com/teastman/node-red-contrib-semaphore ↗

packagenode-red-contrib-semaphore ↗

homepagehttps://github.com/teastman/node-red-contrib-semaphore#readme ↗