Class: Google::Cloud::Pubsub::Topic

Inherits:
Object
  • Object
show all
Defined in:
lib/google/cloud/pubsub/topic.rb,
lib/google/cloud/pubsub/topic/list.rb,
lib/google/cloud/pubsub/topic/publisher.rb

Overview

Topic

A named resource to which messages are published.

Examples:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new

topic = pubsub.topic "my-topic"
topic.publish "task completed"

Defined Under Namespace

Classes: List, Publisher

Instance Method Summary collapse

Instance Method Details

#delete ⇒ Boolean

Permanently deletes the topic.

Examples:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new

topic = pubsub.topic "my-topic"
topic.delete

Returns:

  • (Boolean) —

    Returns true if the topic was deleted.



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# File 'lib/google/cloud/pubsub/topic.rb', line 86

def delete
  ensure_service!
  service.delete_topic name
  true
end

#exists? ⇒ Boolean

Determines whether the topic exists in the Pub/Sub service.

Examples:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new

topic = pubsub.topic "my-topic"
topic.exists? #=> true

Returns:

  • (Boolean) 


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# File 'lib/google/cloud/pubsub/topic.rb', line 424

def exists?
  # Always true if we have a grpc object
  return true unless @grpc.nil?
  # If we have a value, return it
  return @exists unless @exists.nil?
  ensure_grpc!
  @exists = !@grpc.nil?
end

#name ⇒ Object

The name of the topic in the form of "/projects/project-identifier/topics/topic-name".



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# File 'lib/google/cloud/pubsub/topic.rb', line 69

def name
  @grpc ? @grpc.name : @name
end

#policy(force: nil) {|policy| ... } ⇒ Policy

Gets the Cloud IAM access control policy for this topic.

Examples:

Policy values are memoized to reduce the number of API calls:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new
topic = pubsub.topic "my-topic"

policy = topic.policy # API call
policy_2 = topic.policy # No API call

Use force to retrieve the latest policy from the service:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new
topic = pubsub.topic "my-topic"

policy = topic.policy force: true # API call
policy_2 = topic.policy force: true # API call

Update the policy by passing a block:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new
topic = pubsub.topic "my-topic"

policy = topic.policy do |p|
  p.add "roles/owner", "user:owner@example.com"
end # 2 API calls

Parameters:

  • force (Boolean) —

    Force the latest policy to be retrieved from the Pub/Sub service when true. Otherwise the policy will be memoized to reduce the number of API calls made to the Pub/Sub service. The default is false.

Yields:

  • (policy) —

    A block for updating the policy. The latest policy will be read from the Pub/Sub service and passed to the block. After the block completes, the modified policy will be written to the service.

Yield Parameters:

  • policy (Policy) —

    the current Cloud IAM Policy for this topic

Returns:

  • (Policy) —

    the current Cloud IAM Policy for this topic

See Also:



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# File 'lib/google/cloud/pubsub/topic.rb', line 326

def policy force: nil
  @policy = nil if force || block_given?
  @policy ||= begin
    ensure_service!
    grpc = service.get_topic_policy name
    Policy.from_grpc grpc
  end
  return @policy unless block_given?
  p = @policy.deep_dup
  yield p
  self.policy = p
end

#policy=(new_policy) ⇒ Object

Updates the Cloud IAM access control policy for this topic. The policy should be read from #policy. See Policy for an explanation of the policy etag property and how to modify policies.

You can also update the policy by passing a block to #policy, which will call this method internally after the block completes.

Examples:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new
topic = pubsub.topic "my-topic"

policy = topic.policy # API call

policy.add "roles/owner", "user:owner@example.com"

topic.policy = policy # API call

Parameters:

  • new_policy (Policy) —

    a new or modified Cloud IAM Policy for this topic

See Also:



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# File 'lib/google/cloud/pubsub/topic.rb', line 366

def policy= new_policy
  ensure_service!
  grpc = service.set_topic_policy name, new_policy.to_grpc
  @policy = Policy.from_grpc grpc
end

#publish(data = nil, attributes = {}) {|publisher| ... } ⇒ Message+

Publishes one or more messages to the topic.

Examples:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new

topic = pubsub.topic "my-topic"
msg = topic.publish "new-message"

A message can be published using a File object:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new

topic = pubsub.topic "my-topic"
msg = topic.publish File.open("message.txt")

Additionally, a message can be published with attributes:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new

topic = pubsub.topic "my-topic"
msg = topic.publish "new-message",
                    foo: :bar,
                    this: :that

Multiple messages can be sent at the same time using a block:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new

topic = pubsub.topic "my-topic"
msgs = topic.publish do |t|
  t.publish "new-message-1", foo: :bar
  t.publish "new-message-2", foo: :baz
  t.publish "new-message-3", foo: :bif
end

Parameters:

  • data (String, File) (defaults to: nil) —

    The message data.

  • attributes (Hash) (defaults to: {}) —

    Optional attributes for the message.

Yields:

  • (publisher) —

    a block for publishing multiple messages in one request

Yield Parameters:

Returns:

  • (Message, Array<Message>) —

    Returns the published message when called without a block, or an array of messages when called with a block.



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# File 'lib/google/cloud/pubsub/topic.rb', line 269

def publish data = nil, attributes = {}
  ensure_service!
  publisher = Publisher.new data, attributes
  yield publisher if block_given?
  return nil if publisher.messages.count.zero?
  publish_batch_messages publisher
end

#subscribe(subscription_name, deadline: nil, endpoint: nil) ⇒ Google::Cloud::Pubsub::Subscription Also known as: create_subscription, new_subscription

Creates a new Subscription object on the current Topic.

Examples:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new

topic = pubsub.topic "my-topic"
sub = topic.subscribe "my-topic-sub"
puts sub.name # => "my-topic-sub"

Wait 2 minutes for acknowledgement and push all to endpoint:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new

topic = pubsub.topic "my-topic"
sub = topic.subscribe "my-topic-sub",
                      deadline: 120,
                      endpoint: "https://example.com/push"

Parameters:

  • subscription_name (String) —

    Name of the new subscription. Must start with a letter, and contain only letters ([A-Za-z]), numbers ([0-9], dashes (-), underscores (_), periods (.), tildes (~), plus (+) or percent signs (%). It must be between 3 and 255 characters in length, and it must not start with "goog". Required.

  • deadline (Integer) —

    The maximum number of seconds after a subscriber receives a message before the subscriber should acknowledge the message.

  • endpoint (String) —

    A URL locating the endpoint to which messages should be pushed.

Returns:



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# File 'lib/google/cloud/pubsub/topic.rb', line 127

def subscribe subscription_name, deadline: nil, endpoint: nil
  ensure_service!
  options = { deadline: deadline, endpoint: endpoint }
  grpc = service.create_subscription name, subscription_name, options
  Subscription.from_grpc grpc, service
end

#subscription(subscription_name, skip_lookup: nil) ⇒ Google::Cloud::Pubsub::Subscription? Also known as: get_subscription, find_subscription

Retrieves subscription by name.

Examples:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new

topic = pubsub.topic "my-topic"
subscription = topic.subscription "my-topic-subscription"
puts subscription.name

Skip the lookup against the service with skip_lookup:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new

# No API call is made to retrieve the subscription information.
subscription = pubsub.subscription "my-sub", skip_lookup: true
puts subscription.name

Parameters:

  • subscription_name (String) —

    Name of a subscription.

  • skip_lookup (Boolean) —

    Optionally create a Subscription object without verifying the subscription resource exists on the Pub/Sub service. Calls made on this object will raise errors if the service resource does not exist. Default is false.

Returns:



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# File 'lib/google/cloud/pubsub/topic.rb', line 166

def subscription subscription_name, skip_lookup: nil
  ensure_service!
  return Subscription.new_lazy subscription_name, service if skip_lookup
  grpc = service.get_subscription subscription_name
  Subscription.from_grpc grpc, service
rescue Google::Cloud::NotFoundError
  nil
end

#subscriptions(token: nil, max: nil) ⇒ Array<Subscription> Also known as: find_subscriptions, list_subscriptions

Retrieves a list of subscription names for the given project.

Examples:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new

topic = pubsub.topic "my-topic"
subscription = topic.subscriptions
subscriptions.each do |subscription|
  puts subscription.name
end

Retrieve all subscriptions: (See Subscription::List#all)

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new

topic = pubsub.topic "my-topic"
subscription = topic.subscriptions
subscriptions.all do |subscription|
  puts subscription.name
end

Parameters:

  • token (String) —

    The token value returned by the last call to subscriptions; indicates that this is a continuation of a call, and that the system should return the next page of data.

  • max (Integer) —

    Maximum number of subscriptions to return.

Returns:



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# File 'lib/google/cloud/pubsub/topic.rb', line 209

def subscriptions token: nil, max: nil
  ensure_service!
  options = { token: token, max: max }
  grpc = service.list_topics_subscriptions name, options
  Subscription::List.from_topic_grpc grpc, service, name, max
end

#test_permissions(*permissions) ⇒ Array<Strings>

Tests the specified permissions against the Cloud IAM access control policy.

Examples:

require "google/cloud/pubsub"

pubsub = Google::Cloud::Pubsub.new
topic = pubsub.topic "my-topic"
perms = topic.test_permissions "pubsub.topics.get",
                               "pubsub.topics.publish"
perms.include? "pubsub.topics.get" #=> true
perms.include? "pubsub.topics.publish" #=> false

Parameters:

  • permissions (String, Array<String>) —

    The set of permissions to check access for. Permissions with wildcards (such as * or storage.*) are not allowed.

    The permissions that can be checked on a topic are:

    • pubsub.topics.publish
    • pubsub.topics.attachSubscription
    • pubsub.topics.get
    • pubsub.topics.delete
    • pubsub.topics.update
    • pubsub.topics.getIamPolicy
    • pubsub.topics.setIamPolicy

Returns:

  • (Array<Strings>) —

    The permissions that have access.

See Also:



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# File 'lib/google/cloud/pubsub/topic.rb', line 405

def test_permissions *permissions
  permissions = Array(permissions).flatten
  permissions = Array(permissions).flatten
  ensure_service!
  grpc = service.test_topic_permissions name, permissions
  grpc.permissions
end