A Topic object allows you to interact with a Cloud Pub/Sub topic.
Package
@google-cloud/pubsub
Examples
const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
To enable message ordering, set enableMessageOrdering
to true. Please note that this does not persist to an actual topic.
const
topic
=
pubsub
.
topic
(
'ordered-topic'
,
{
enableMessageOrdering
:
true
});
Constructors
(constructor)(pubsub, name, options)
constructor
(
pubsub
:
PubSub
,
name
:
string
,
options
?:
PublishOptions
);
Constructs a new instance of the Topic
class
Parameters
Properties
getSubscriptionsStream
getSubscriptionsStream
:
()
=
>
ObjectStream<Subscription>
;
Property Value
iam
Property Value
metadata
?:
TopicMetadata
;
Property Value
name
Property Value
parent
Property Value
publisher
Property Value
pubsub
Property Value
request
request
:
typeof
PubSub
.
prototype
.
request
;
Property Value
Methods
create(gaxOpts)
create
(
gaxOpts
?:
CallOptions
)
:
Promise<CreateTopicResponse>
;
Parameter
Returns
Example const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
topic
.
create
((
err
,
topic
,
apiResponse
)
=
>
{
if
(
!
err
)
{
// The topic was created successfully.
}
});
//-
// If the callback is omitted, we'll return a Promise.
//-
topic
.
create
().
then
((
data
)
=
>
{
const
topic
=
data
[
0
];
const
apiResponse
=
data
[
1
];
});
create(callback)
create
(
callback
:
CreateTopicCallback
)
:
void
;
Parameter
Returns
create(gaxOpts, callback)
create
(
gaxOpts
:
CallOptions
,
callback
:
CreateTopicCallback
)
:
void
;
Parameters
Returns
createSubscription(name, callback)
createSubscription
(
name
:
string
,
callback
:
CreateSubscriptionCallback
)
:
void
;
Create a subscription to this topic.
Parameters
Returns
Example const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
const
callback
=
function
(
err
,
subscription
,
apiResponse
)
{};
// Without specifying any options.
topic
.
createSubscription
(
'newMessages'
,
callback
);
// With options.
topic
.
createSubscription
(
'newMessages'
,
{
ackDeadlineSeconds
:
90
},
callback
);
//-
// If the callback is omitted, we'll return a Promise.
//-
topic
.
createSubscription
(
'newMessages'
).
then
((
data
)
=
>
{
const
subscription
=
data
[
0
];
const
apiResponse
=
data
[
1
];
});
createSubscription(name, options)
createSubscription
(
name
:
string
,
options
?:
CreateSubscriptionOptions
)
:
Promise<CreateSubscriptionResponse>
;
Parameters
Returns
createSubscription(name, options, callback)
createSubscription
(
name
:
string
,
options
:
CreateSubscriptionOptions
,
callback
:
CreateSubscriptionCallback
)
:
void
;
Parameters
Returns
delete(callback)
delete
(
callback
:
EmptyCallback
)
:
void
;
Delete the topic. This will not delete subscriptions to this topic.
Parameter
Returns
Example const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
topic
.
delete
((
err
,
apiResponse
)
=
>
{});
//-
// If the callback is omitted, we'll return a Promise.
//-
topic
.
delete
().
then
((
data
)
=
>
{
const
apiResponse
=
data
[
0
];
});
delete(gaxOpts)
delete
(
gaxOpts
?:
CallOptions
)
:
Promise<EmptyResponse>
;
Parameter
Returns
delete(gaxOpts, callback)
delete
(
gaxOpts
:
CallOptions
,
callback
:
EmptyCallback
)
:
void
;
Parameters
Returns
exists()
exists
()
:
Promise<ExistsResponse>
;
Returns
Example const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
topic
.
exists
((
err
,
exists
)
=
>
{});
//-
// If the callback is omitted, we'll return a Promise.
//-
topic
.
exists
().
then
((
data
)
=
>
{
const
exists
=
data
[
0
];
});
exists(callback)
exists
(
callback
:
ExistsCallback
)
:
void
;
Parameter
Returns
flowControlled()
flowControlled
()
:
FlowControlledPublisher
;
Creates a FlowControlledPublisher for this Topic.
FlowControlledPublisher is a helper that lets you control how many messages are simultaneously queued to send, to avoid ballooning memory usage on a low bandwidth connection to Pub/Sub.
Note that it's perfectly fine to create more than one on the same Topic. The actual flow control settings on the Topic will apply across all FlowControlledPublisher objects on that Topic.
Returns | Type |
Description |
| FlowControlledPublisher
|
{FlowControlledPublisher} The flow control helper.
|
flush()
flush
()
:
Promise<void>
;
Immediately sends all remaining queued data. This is mostly useful if you are planning to call close() on the PubSub object that holds the server connections.
Returns
flush(callback)
flush
(
callback
:
EmptyCallback
)
:
void
;
Parameter
Returns
static
formatName_
(
projectId
:
string
,
name
:
string
)
:
string
;
Format the name of a topic. A Topic's full name is in the format of 'projects/{projectId}/topics/{topicName}'.
{string}
Parameters
Returns
get(callback)
get
(
callback
:
GetTopicCallback
)
:
void
;
Get a topic if it exists.
Parameter
Returns
Example const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
topic
.
get
((
err
,
topic
,
apiResponse
)
=
>
{
// The `topic` data has been populated.
});
//-
// If the callback is omitted, we'll return a Promise.
//-
topic
.
get
().
then
((
data
)
=
>
{
const
topic
=
data
[
0
];
const
apiResponse
=
data
[
1
];
});
get(gaxOpts)
get
(
gaxOpts
?:
GetTopicOptions
)
:
Promise<GetTopicResponse>
;
Parameter
Returns
get(gaxOpts, callback)
get
(
gaxOpts
:
GetTopicOptions
,
callback
:
GetTopicCallback
)
:
void
;
Parameters
Returns
getMetadata
(
callback
:
GetTopicMetadataCallback
)
:
void
;
Get the official representation of this topic from the API.
Parameter
Returns
Example const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
topic
.
getMetadata
((
err
,
apiResponse
)
=
>
{});
//-
// If the callback is omitted, we'll return a Promise.
//-
topic
.
getMetadata
().
then
((
data
)
=
>
{
const
apiResponse
=
data
[
0
];
});
getMetadata
(
gaxOpts
:
CallOptions
,
callback
:
GetTopicMetadataCallback
)
:
void
;
Parameters
Returns
getMetadata
(
gaxOpts
?:
CallOptions
)
:
Promise<GetTopicMetadataResponse>
;
Parameter
Returns
getPublishOptionDefaults()
getPublishOptionDefaults
()
:
PublishOptions
;
Get the default publisher options. These may be modified and passed back into .
Returns
Example const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
const
defaults
=
topic
.
getPublishOptionDefaults
();
defaults
.
batching
.
maxMilliseconds
=
10
;
topic
.
setPublishOptions
(
defaults
);
getSubscriptions(callback)
getSubscriptions
(
callback
:
GetTopicSubscriptionsCallback
)
:
void
;
Get a list of the subscriptions registered to this topic. You may optionally provide a query object as the first argument to customize the response.
Your provided callback will be invoked with an error object if an API error occurred or an array of {module:pubsub/subscription} objects.
Parameter
Returns
Example const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
topic
.
getSubscriptions
((
err
,
subscriptions
)
=
>
{
// subscriptions is an array of `Subscription` objects.
});
// Customize the query.
topic
.
getSubscriptions
({
pageSize
:
3
},
callback
);
//-
// If the callback is omitted, we'll return a Promise.
//-
topic
.
getSubscriptions
().
then
((
data
)
=
>
{
const
subscriptions
=
data
[
0
];
});
getSubscriptions(options, callback)
getSubscriptions
(
options
:
PageOptions
,
callback
:
GetTopicSubscriptionsCallback
)
:
void
;
Parameters
Returns
getSubscriptions(options)
getSubscriptions
(
options
?:
PageOptions
)
:
Promise<GetTopicSubscriptionsResponse>
;
Parameter
Returns
publish(data, attributes)
publish
(
data
:
Buffer
,
attributes
?:
Attributes
)
:
Promise<string>
;
Publish the provided message.
Parameters | Name |
Description |
| data |
Buffer
The message data. This must come in the form of a Buffer object.
|
| attributes |
Attributes
Attributes for this message.
|
Returns
Examples const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
const
data
=
Buffer
.
from
(
'Hello, world!'
);
const
callback
=
(
err
,
messageId
)
=
>
{
if
(
err
)
{
// Error handling omitted.
}
};
topic
.
publish
(
data
,
callback
);
Optionally you can provide an object containing attributes for the message. Note that all values in the object must be strings.
const
attributes
=
{
key
:
'value'
};
topic
.
publish
(
data
,
attributes
,
callback
);
If the callback is omitted, we'll return a Promise.
topic
.
publish
(
data
).
then
((
messageId
)
=
>
{});
publish(data, callback)
publish
(
data
:
Buffer
,
callback
:
PublishCallback
)
:
void
;
Parameters
Returns
publish(data, attributes, callback)
publish
(
data
:
Buffer
,
attributes
:
Attributes
,
callback
:
PublishCallback
)
:
void
;
Parameters
Returns
publishJSON(json, attributes)
publishJSON
(
json
:
object
,
attributes
?:
Attributes
)
:
Promise<string>
;
Publish the provided JSON. It should be noted that all messages published are done so in the form of a Buffer. This is simply a convenience method that will transform JSON into a Buffer before publishing. Subscription
objects will always return message data in the form of a Buffer, so any JSON published will require manual deserialization.
Parameters | Name |
Description |
| json |
object
The JSON data to publish.
|
| attributes |
Attributes
Attributes for this message.
|
Returns
Examples const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
const
data
=
{
foo
:
'bar'
};
const
callback
=
(
err
,
messageId
)
=
>
{
if
(
err
)
{
// Error handling omitted.
}
};
topic
.
publishJSON
(
data
,
callback
);
Optionally you can provide an object containing attributes for the message. Note that all values in the object must be strings.
const
attributes
=
{
key
:
'value'
};
topic
.
publishJSON
(
data
,
attributes
,
callback
);
If the callback is omitted, we'll return a Promise.
topic
.
publishJSON
(
data
).
then
((
messageId
)
=
>
{});
publishJSON(json, callback)
publishJSON
(
json
:
object
,
callback
:
PublishCallback
)
:
void
;
Parameters
Returns
publishJSON(json, attributes, callback)
publishJSON
(
json
:
object
,
attributes
:
Attributes
,
callback
:
PublishCallback
)
:
void
;
Parameters
Returns
publishMessage(message)
publishMessage
(
message
:
MessageOptions
)
:
Promise
< [
string
]>;
Publish the provided message.
Parameter | Name |
Description |
| message |
MessageOptions
Message object.
|
Returns
Examples const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
const
data
=
Buffer
.
from
(
'Hello, world!'
);
const
callback
=
(
err
,
messageId
)
=
>
{
if
(
err
)
{
// Error handling omitted.
}
};
topic
.
publishMessage
({
data
},
callback
);
Publish JSON message data.
const
json
=
{
foo
:
'bar'
};
topic
.
publishMessage
({
json
},
callback
);
To publish messages in order (this is still experimental), make sure message ordering is enabled and provide an ordering key
const
topic
=
pubsub
.
topic
(
'ordered-topic'
,
{
messageOrdering
:
true
});
const
orderingKey
=
'my-key'
;
topic
.
publishMessage
({
data
,
orderingKey
},
callback
);
If the callback is omitted, we'll return a Promise.
const
[
messageId
]
=
await
topic
.
publishMessage
({
data
});
publishMessage(message, callback)
publishMessage
(
message
:
MessageOptions
,
callback
:
PublishCallback
)
:
void
;
Parameters
Returns
resumePublishing(orderingKey)
resumePublishing
(
orderingKey
:
string
)
:
void
;
In the event that the client fails to publish an ordered message, all subsequent publish calls using the same ordering key will fail. Calling this method will disregard the publish failure, allowing the supplied ordering key to be used again in the future.
Parameter | Name |
Description |
| orderingKey |
string
The ordering key in question.
|
Returns
Example const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
,
{
messageOrdering
:
true
});
const
orderingKey
=
'foo'
;
const
data
=
Buffer
.
from
(
'Hello, order!'
);
topic
.
publishMessage
({
data
,
orderingKey
},
err
=
>
{
if
(
err
)
{
topic
.
resumePublishing
(
orderingKey
);
}
});
setMetadata
(
options
:
TopicMetadata
,
gaxOpts
?:
CallOptions
)
:
Promise<SetTopicMetadataResponse>
;
Parameters
Returns
Examples const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
const
metadata
=
{
labels
:
{
foo
:
'bar'
}
};
topic
.
setMetadata
(
metadata
,
err
=
>
{
if
(
err
)
{
// Error handling omitted.
}
});
If the callback is omitted, we'll return a Promise.
topic
.
setMetadata
(
metadata
).
then
((
data
)
=
>
{
const
apiResponse
=
data
[
0
];
});
setMetadata
(
options
:
TopicMetadata
,
callback
:
SetTopicMetadataCallback
)
:
void
;
Parameters
Returns
setMetadata
(
options
:
TopicMetadata
,
gaxOpts
:
CallOptions
,
callback
:
SetTopicMetadataCallback
)
:
void
;
Parameters
Returns
setPublishOptions(options)
setPublishOptions
(
options
:
PublishOptions
)
:
void
;
Set the publisher options.
Parameter
Returns
Example const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
topic
.
setPublishOptions
({
batching
:
{
maxMilliseconds
:
10
}
});
subscription(name, options)
subscription
(
name
:
string
,
options
?:
SubscriptionOptions
)
:
Subscription
;
Create a Subscription object. This command by itself will not run any API requests. You will receive a {module:pubsub/subscription} object, which will allow you to interact with a subscription.
Parameters | Name |
Description |
| name |
string
Name of the subscription.
|
| options |
SubscriptionOptions
Configuration object. {Subscription}
|
Returns
Example const
{
PubSub
}
=
require
(
' @google-cloud/pubsub
'
);
const
pubsub
=
new
PubSub
();
const
topic
=
pubsub
.
topic
(
'my-topic'
);
const
subscription
=
topic
.
subscription
(
'my-subscription'
);
// Register a listener for `message` events.
subscripti on
.
on
(
'message'
,
(
message
)
=
>
{
// Called every time a message is received.
// message.id = ID of the message.
// message.ackId = ID used to acknowledge the message receival.
// message.data = Contents of the message.
// message.attributes = Attributes of the message.
// message.publishTime = Timestamp when Pub/Sub received the message.
});
