pubsubc

A simple command-line client for Google Cloud Pub/Sub.

Unlike the gcloud pubsub utility, pubsubc:

• Supports the Pub/Sub emulator
• Provides a continuous subscribe command - to see all messages as they come in

Since this was originally created as a learning exercise for integrating to Pub/Sub, the source code should be simple enough for you to copy and adapt into your own application.

Contents

• Intro
• Installation
  • Direct
  • Bundler
• Usage
  • Subscribe
  • Publish message
  • Publish generated messages
• Example
  • Communicating some messages
  • Publishing from a message generator with several subscribers
• Help info
• Contributing
• Development
  • Pub/Sub emulator
  • Pre-push hook
  • Release

Intro

Features:

• Subscribe to a topic, continuously logging all messages as they arrive
• Publish a string message to a topic (creating a subscription automatically)
• Publish automatically-generated messages continuously at a given interval
• Supports connecting to either a local emulator or the remote real Pub/Sub

Installation

The executable is distributed through RubyGems.

Direct

You can install it to your system directly using:

gem install pubsubc

And then if you're using rbenv:

rbenv rehash

You can then run it with:

pubsubc

Bundler

Or, just add it to the Gemfile of your project:

gem 'pubsubc'

And then run it with:

bundle exec pubsubc

Usage

Subscribe

To subscribe and continuously log all messages from the topic:

pubsubc sub

Publish message

To publish a single message to the topic:

pubsubc pub msg "G'day"

Publish generated messages

To publish a generated message to the topic every second:

pubsubc pub gen --interval 1000

Example

Communicating some messages

➜ pubsubc pub msg "Sup wigga"    
Initialising Pub/Sub client for emulator (localhost:8085)... done
Checking existence of topic 'my-topic'... creating... done
Checking existence of subscription 'my-subscription'... creating... done
Published message: Sup wigga

➜ pubsubc pub msg "Yo J-dog" 
Initialising Pub/Sub client for emulator (localhost:8085)... done
Checking existence of topic 'my-topic'... exists
Checking existence of subscription 'my-subscription'... exists
Published message: Yo J-dog

➜ pubsubc sub                
Initialising Pub/Sub client for emulator (localhost:8085)... done
Checking existence of topic 'my-topic'... exists
Checking existence of subscription 'my-subscription'... exists
Listening for messages
Data: Sup wigga, published at 2021-07-30 23:19:06 +1000
Data: Yo J-dog, published at 2021-07-30 23:19:41 +1000
^C

Publishing from a message generator with several subscribers

The generator was run with:

pubsubc pub gen --interval 1

And each subscriber:

pubsubc sub

Help info

Output of pubsubc --help:

Usage:
    pubsubc [OPTIONS] SUBCOMMAND [ARG] ...

  A simple command-line client for Google Cloud Pub/Sub.

  Created as a learning exercise, but also useful since the 'gcloud pubsub' commands don't support the emulator, and it doesn't provide a continuous subscribe command.

  To clean up:

      gcloud pubsub topics delete my-topic
      gcloud pubsub subscriptions delete my-subscription

Parameters:
    SUBCOMMAND                          subcommand
    [ARG] ...                           subcommand arguments

Subcommands:
    pub                                 Publishing messages to the topic
    sub                                 Subscribe to messages on the topic
    shell                               Get a Ruby shell to interact with Pub/Sub

Options:
    --topic TOPIC_NAME                  The name of the Pub/Sub topic (default: "my-topic")
    --subscription SUBSCRIPTION_NAME    The name of the Pub/Sub subscription within the topic (default: "my-subscription")
    --remote                            Connect to the real Pub/Sub, rather than a local Pub/Sub emulator
    --emulator-host EMULATOR_HOST       The host and port of the Pub/Sub emulator (default: $PUBSUB_EMULATOR_HOST, or "localhost:8085")
    -h, --help                          print help

Suffix --help to any subcommand to see the usage info for it.

Contributing

Pull requests welcome! =)

However, I don't intend to duplicate functionality that exists in the gcloud pubsub utility, unless it's an improvement over what's in that.

Development

Pub/Sub emulator

To run the Pub/Sub emulator (with Docker):

docker-compose up -d pubsub-emulator

Pre-push hook

This hook runs style checks and tests.

To set up the pre-push hook:

echo -e "#\!/bin/bash\n\$(dirname \$0)/../../auto/pre-push-hook" > .git/hooks/pre-push
chmod +x .git/hooks/pre-push

Release

To release a new version:

auto/release/update-version && auto/release/tag && auto/release/publish

This takes care of the whole process:

• Incrementing the version number (the patch number by default)
• Tagging & pushing commits
• Publishing the gem to RubyGems
• Creating a draft GitHub release

To increment the minor or major versions instead of the patch number, run auto/release/update-version with --minor or --major.