Class: Gcloud::Pubsub::Subscription

Inherits:
Object
  • Object
show all
Defined in:
lib/gcloud/pubsub/subscription.rb,
lib/gcloud/pubsub/subscription/list.rb

Overview

Subscription

A named resource representing the stream of messages from a single, specific topic, to be delivered to the subscribing application.

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

sub = pubsub.subscription "my-topic-sub"
msgs = sub.pull
msgs.each { |msg| msg.acknowledge! }

Defined Under Namespace

Classes: List

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Subscription

Create an empty Subscription object.



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# File 'lib/gcloud/pubsub/subscription.rb', line 48

def initialize #:nodoc:
  @connection = nil
  @gapi = {}
  @name = nil
  @exists = nil
end

Instance Attribute Details

#connection ⇒ Object

The Connection object.



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# File 'lib/gcloud/pubsub/subscription.rb', line 40

def connection
  @connection
end

#gapi ⇒ Object

The Google API Client object.



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# File 'lib/gcloud/pubsub/subscription.rb', line 44

def gapi
  @gapi
end

Class Method Details

.from_gapi(gapi, conn) ⇒ Object

New Subscription from a Google API Client object.



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# File 'lib/gcloud/pubsub/subscription.rb', line 567

def self.from_gapi gapi, conn #:nodoc:
  new.tap do |f|
    f.gapi = gapi
    f.connection = conn
  end
end

.new_lazy(name, conn, options = {}) ⇒ Object

New lazy Topic object without making an HTTP request.



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# File 'lib/gcloud/pubsub/subscription.rb', line 57

def self.new_lazy name, conn, options = {} #:nodoc:
  sub = new.tap do |f|
    f.gapi = nil
    f.connection = conn
  end
  sub.instance_eval do
    @name = conn.subscription_path(name, options)
  end
  sub
end

Instance Method Details

#acknowledge(*messages) ⇒ Object Also known as: ack

Acknowledges receipt of a message. After an ack, the Pub/Sub system can remove the message from the subscription. Acknowledging a message whose ack deadline has expired may succeed, although the message may have been sent again. Acknowledging a message more than once will not result in an error. This is only used for messages received via pull.

Parameters

messages

One or more ReceivedMessage objects or ack_id values. (ReceivedMessage or ack_id)

Example

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

sub = pubsub.subscription "my-topic-sub"
messages = sub.pull
sub.acknowledge messages



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# File 'lib/gcloud/pubsub/subscription.rb', line 408

def acknowledge *messages
  ack_ids = coerce_ack_ids messages
  ensure_connection!
  resp = connection.acknowledge name, *ack_ids
  if resp.success?
    true
  else
    fail ApiError.from_response(resp)
  end
end

#deadline ⇒ Object

This value is the maximum number of seconds after a subscriber receives a message before the subscriber should acknowledge the message.



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# File 'lib/gcloud/pubsub/subscription.rb', line 101

def deadline
  ensure_gapi!
  @gapi["ackDeadlineSeconds"]
end

#delay(new_deadline, *messages) ⇒ Object

Modifies the acknowledge deadline for messages.

This indicates that more time is needed to process the messages, or to make the messages available for redelivery if the processing was interrupted.

Parameters

new_deadline

The new ack deadline in seconds from the time this request is sent to the Pub/Sub system. Must be >= 0. For example, if the value is 10, the new ack deadline will expire 10 seconds after the call is made. Specifying 0 may immediately make the messages available for another pull request. (Integer)

messages

One or more ReceivedMessage objects or ack_id values. (ReceivedMessage or ack_id)

Example

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

sub = pubsub.subscription "my-topic-sub"
messages = sub.pull
sub.delay 120, messages



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# File 'lib/gcloud/pubsub/subscription.rb', line 450

def delay new_deadline, *messages
  ack_ids = coerce_ack_ids messages
  ensure_connection!
  resp = connection.modify_ack_deadline name, ack_ids, new_deadline
  if resp.success?
    true
  else
    fail ApiError.from_response(resp)
  end
end

#delete ⇒ Object

Deletes an existing subscription. All pending messages in the subscription are immediately dropped.

Returns

true if the subscription was deleted.

Example

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

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



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# File 'lib/gcloud/pubsub/subscription.rb', line 186

def delete
  ensure_connection!
  resp = connection.delete_subscription name
  if resp.success?
    true
  else
    fail ApiError.from_response(resp)
  end
end

#endpoint ⇒ Object

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



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# File 'lib/gcloud/pubsub/subscription.rb', line 109

def endpoint
  ensure_gapi!
  @gapi["pushConfig"]["pushEndpoint"] if @gapi["pushConfig"]
end

#endpoint=(new_endpoint) ⇒ Object

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



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# File 'lib/gcloud/pubsub/subscription.rb', line 116

def endpoint= new_endpoint
  ensure_connection!
  resp = connection.modify_push_config name, new_endpoint, {}
  if resp.success?
    @gapi["pushConfig"]["pushEndpoint"] = new_endpoint if @gapi
  else
    fail ApiError.from_response(resp)
  end
end

#exists? ⇒ Boolean

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

Example

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

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

Returns:

  • (Boolean) 


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# File 'lib/gcloud/pubsub/subscription.rb', line 139

def exists?
  # Always true if we have a gapi object
  return true unless @gapi.nil?
  # If we have a value, return it
  return @exists unless @exists.nil?
  ensure_gapi!
  @exists = !@gapi.nil?
rescue NotFoundError
  @exists = false
end

#lazy? ⇒ Boolean

Determines whether the subscription object was created with an HTTP call.

Example

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

sub = pubsub.get_subscription "my-topic-sub"
sub.lazy? #=> false

Returns:

  • (Boolean) 


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# File 'lib/gcloud/pubsub/subscription.rb', line 164

def lazy? #:nodoc:
  @gapi.nil?
end

#listen(options = {}) ⇒ Object

Poll the backend for new messages. This runs a loop to ping the API, blocking indefinitely, yielding retrieved messages as they are received.

Parameters

options

An optional Hash for controlling additional behavior. (Hash)

options[:max]

The maximum number of messages to return for this request. The Pub/Sub system may return fewer than the number specified. The default value is 100, the maximum value is 1000. (Integer)

options[:autoack]

Automatically acknowledge the message as it is pulled. The default value is false. (Boolean)

options[:delay]

The number of seconds to pause between requests when the Google Cloud service has no messages to return. The default value is 1. (Number)

Examples

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

sub = pubsub.subscription "my-topic-sub"
sub.listen do |msg|
  # process msg
end

The number of messages pulled per batch can be set with the max option:

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

sub = pubsub.subscription "my-topic-sub"
sub.listen max: 20 do |msg|
  # process msg
end

Messages can be automatically acknowledged as they are pulled with the autoack option:

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

sub = pubsub.subscription "my-topic-sub"
sub.listen autoack: true do |msg|
  # process msg
end



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# File 'lib/gcloud/pubsub/subscription.rb', line 371

def listen options = {}
  delay = options.fetch(:delay, 1)
  loop do
    msgs = wait_for_messages options
    if msgs.any?
      msgs.each { |msg| yield msg }
    else
      sleep delay
    end
  end
end

#name ⇒ Object

The name of the subscription.



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# File 'lib/gcloud/pubsub/subscription.rb', line 70

def name
  @gapi ? @gapi["name"] : @name
end

#policy(options = {}) ⇒ Object

Gets the access control policy.

Parameters

options

An optional Hash for controlling additional behavior. (Hash)

options[:force]

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. (Boolean)

Returns

A hash that conforms to the following structure:

{
  "bindings" => [{
    "role" => "roles/viewer",
    "members" => ["serviceAccount:your-service-account"]
  }],
  "rules" => []
}

Examples

By default, the policy values are memoized to reduce the number of API calls to the Pub/Sub service.

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

subscription = pubsub.subscription "my-subscription"
puts subscription.policy["bindings"]
puts subscription.policy["rules"]

To retrieve the latest policy from the Pub/Sub service, use the force flag.

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

subscription = pubsub.subscription "my-subscription"
policy = subscription.policy force: true



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# File 'lib/gcloud/pubsub/subscription.rb', line 511

def policy options = {}
  @policy = nil if options[:force]
  @policy ||= begin
    ensure_connection!
    resp = connection.get_subscription_policy name
    policy = resp.data["policy"]
    policy = policy.to_hash if policy.respond_to? :to_hash
    policy
  end
end

#policy=(new_policy) ⇒ Object

Sets the access control policy.

Parameters

new_policy

A hash that conforms to the following structure:

{
  "bindings" => [{
    "role" => "roles/viewer",
    "members" => ["serviceAccount:your-service-account"]
  }],
  "rules" => []
}

Example

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

viewer_policy = {
  "bindings" => [{
    "role" => "roles/viewer",
    "members" => ["serviceAccount:your-service-account"]
  }]
}
subscription = pubsub.subscription "my-subscription"
subscription.policy = viewer_policy



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# File 'lib/gcloud/pubsub/subscription.rb', line 554

def policy= new_policy
  ensure_connection!
  resp = connection.set_subscription_policy name, new_policy
  if resp.success?
    @policy = resp.data["policy"]
    @policy = @policy.to_hash if @policy.respond_to? :to_hash
  else
    fail ApiError.from_response(resp)
  end
end

#pull(options = {}) ⇒ Object

Pulls messages from the server. Returns an empty list if there are no messages available in the backlog. Raises an ApiError with status UNAVAILABLE if there are too many concurrent pull requests pending for the given subscription.

Parameters

options

An optional Hash for controlling additional behavior. (Hash)

options[:immediate]

When true the system will respond immediately even if it is not able to return messages. When false the system is allowed to wait until it can return least one message. No messages are returned when a request times out. The default value is true. (Boolean)

options[:max]

The maximum number of messages to return for this request. The Pub/Sub system may return fewer than the number specified. The default value is 100, the maximum value is 1000. (Integer)

options[:autoack]

Automatically acknowledge the message as it is pulled. The default value is false. (Boolean)

Returns

Array of Gcloud::Pubsub::ReceivedMessage

Examples

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

sub = pubsub.subscription "my-topic-sub"
sub.pull.each { |msg| msg.acknowledge! }

A maximum number of messages returned can also be specified:

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

sub = pubsub.subscription "my-topic-sub", max: 10
sub.pull.each { |msg| msg.acknowledge! }

The call can block until messages are available by setting the :immediate option to false:

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

sub = pubsub.subscription "my-topic-sub"
msgs = sub.pull immediate: false
msgs.each { |msg| msg.acknowledge! }



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# File 'lib/gcloud/pubsub/subscription.rb', line 258

def pull options = {}
  ensure_connection!
  resp = connection.pull name, options
  if resp.success?
    messages = Array(resp.data["receivedMessages"]).map do |gapi|
      ReceivedMessage.from_gapi gapi, self
    end
    acknowledge messages if options[:autoack]
    messages
  else
    fail ApiError.from_response(resp)
  end
rescue Faraday::TimeoutError
  []
end

#topic ⇒ Object

The Topic from which this subscription receives messages.

Returns

Topic

Example

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

sub = pubsub.subscription "my-topic-sub"
sub.topic.name #=> "projects/my-project/topics/my-topic"



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# File 'lib/gcloud/pubsub/subscription.rb', line 91

def topic
  ensure_gapi!
  # Always disable autocreate, we don't want to recreate a topic that
  # was intentionally deleted.
  Topic.new_lazy @gapi["topic"], connection, autocreate: false
end

#wait_for_messages(options = {}) ⇒ Object

Pulls from the server while waiting for messages to become available. This is the same as:

subscription.pull immediate: false

Parameters

options

An optional Hash for controlling additional behavior. (Hash)

options[:max]

The maximum number of messages to return for this request. The Pub/Sub system may return fewer than the number specified. The default value is 100, the maximum value is 1000. (Integer)

options[:autoack]

Automatically acknowledge the message as it is pulled. The default value is false. (Boolean)

Returns

Array of Gcloud::Pubsub::ReceivedMessage

Example

require "gcloud"

gcloud = Gcloud.new
pubsub = gcloud.pubsub

sub = pubsub.subscription "my-topic-sub"
msgs = sub.wait_for_messages
msgs.each { |msg| msg.acknowledge! }



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# File 'lib/gcloud/pubsub/subscription.rb', line 309

def wait_for_messages options = {}
  pull options.merge(immediate: false)
end