workaround for Google Cloud Pub/Sub via google-api-client.gem

Gemfile

source "https://rubygems.org"

gem "google-api-client", "0.8.3"

Gemfile.lock

GEM
  remote: https://rubygems.org/
  specs:
    activesupport (4.2.1)
      i18n (~> 0.7)
      json (~> 1.7, >= 1.7.7)
      minitest (~> 5.1)
      thread_safe (~> 0.3, >= 0.3.4)
      tzinfo (~> 1.1)
    addressable (2.3.7)
    autoparse (0.3.3)
      addressable (>= 2.3.1)
      extlib (>= 0.9.15)
      multi_json (>= 1.0.0)
    extlib (0.9.16)
    faraday (0.9.1)
      multipart-post (>= 1.2, < 3)
    google-api-client (0.8.2)
      activesupport (>= 3.2)
      addressable (~> 2.3)
      autoparse (~> 0.3)
      extlib (~> 0.9)
      faraday (~> 0.9)
      launchy (~> 2.4)
      multi_json (~> 1.10)
      retriable (~> 1.4)
      signet (~> 0.6)
    i18n (0.7.0)
    json (1.8.2)
    jwt (1.4.1)
    launchy (2.4.3)
      addressable (~> 2.3)
    minitest (5.5.1)
    multi_json (1.11.0)
    multipart-post (2.0.0)
    retriable (1.4.1)
    signet (0.6.0)
      addressable (~> 2.3)
      extlib (~> 0.9)
      faraday (~> 0.9)
      jwt (~> 1.0)
      multi_json (~> 1.10)
    thread_safe (0.3.5)
    tzinfo (1.2.2)
      thread_safe (~> 0.1)

PLATFORMS
  ruby

DEPENDENCIES
  google-api-client

publisher.rb

# google-api-client.gem seems have some known issues which could encountered while using Cloud Pub/Sub
require "base64"
require "google/api_client"

auth_params = {
  token_credential_uri: "https://accounts.google.com/o/oauth2/token",
  audience: "https://accounts.google.com/o/oauth2/token",
  scope: "https://www.googleapis.com/auth/pubsub",
  issuer: ENV["SERVICE_ACCOUNT_EMAIL"],
  signing_key: Google::APIClient::PKCS12.load_key(Base64.decode64(ENV["SERVICE_ACCOUNT_P12_KEY_BASE64"]), "notasecret")
}
client = Google::APIClient.new(application_name: "pubsubtest", application_version: "v1",
                               authorization: Signet::OAuth2::Client.new(auth_params))
client.authorization.fetch_access_token!

pubsub_api = client.discovered_api("pubsub", "v1beta2")

# workaround for an issue https://github.com/google/google-api-ruby-client/issues/195
pubsub_api.method_base = "https://pubsub.googleapis.com/v1beta2/"
# workaround for an issue publish discovery_docuent["path"] contains colon and Addressable::URI doesn't treat it as path
pubsub_api.projects.topics.publish.discovery_document["path"] = "/v1beta2/{+topic}:publish"

r = client.execute(api_method: pubsub_api.projects.topics.list, parameters: { project: "projects/#{ENV["PROJECT"]}" })
if r.success?
  puts "Topic List:"
  p r.data.topics.map(&:name)
else
  p r.data.error
  raise "fail to get topic list"
end

puts "enter messages:"
while l = $stdin.gets
  r = client.execute(api_method: pubsub_api.projects.topics.publish, parameters: { topic: "projects/scenic-doodad-617/topics/mytopic" },
                     body_object: { messages: [{ data: Base64.strict_encode64(l.chomp) }] })
  if r.error?
    p r.data.error
    raise "fail to publish"
  end
end