ballerina/websub module
Module overview
This module contains an implementation of the W3C WebSub recommendation, which facilitates a push-based content delivery/notification mechanism between publishers and subscribers.
This implementation supports introducing all WebSub components: subscribers, publishers, and hubs.
- Subscriber - A party interested in receiving update notifications for particular topics.
- Publisher - A party that advertises topics to which interested parties subscribe in order to receive notifications on occurrence of events.
- Hub - A party that accepts subscription requests from subscribers and delivers content to the subscribers when the topic is updated by the topic's publisher.
Basic flow with WebSub
-
The subscriber discovers from the publisher, the topic it needs to subscribe to and the hub(s) that deliver notifications on updates of the topic.
-
The subscriber sends a subscription request to one or more discovered hub(s) specifying the discovered topic along with other subscription parameters such as:
- The callback URL to which content is expected to be delivered.
- (Optional) The lease period (in seconds) the subscriber wants the subscription to stay active.
- (Optional) A secret to use for authenticated content distribution.
-
The hub sends an intent verification request to the specified callback URL. If the response indicates verification (by echoing a challenge specified in the request) by the subscriber, the subscription is added for the topic at the hub.
-
The publisher notifies the hub of updates to the topic and the content to deliver is identified.
-
The hub delivers the identified content to the subscribers of the topic.
Features
Subscriber
This module allows introducing a WebSub Subscriber Service with onIntentVerification
, which accepts HTTP GET requests for intent verification, and onNotification
, which accepts HTTP POST requests for notifications. The WebSub Subscriber Service provides the following capabilities:
- When the service is started a subscription request is sent for a hub/topic combination, either specified as annotations or discovered based on the resource URL specified as an annotation.
- If
onIntentVerification
is not specified, intent verification will be done automatically against the topic specified as an annotation or discovered based on the resource URL specified as an annotation. - If a secret is specified for the subscription, signature validation will be done for authenticated content distribution.
Hub
A WebSub compliant hub based on the Ballerina Message Broker is also available. This can be used as a remote hub or to be used by publishers who want to have their own internal hub. Ballerina's WebSub hub honors specified lease periods and supports authenticated content distribution.
Enabling Basic Auth support for the hub
The Ballerina WebSub Hub can be secured by enforcing authentication (Basic Authentication) and optionally authorization.
AuthProvider
and authConfig
need to be specified for the hub listener and service respectively. If the
authStoreProvider
of the AuthProvider
is set as "http:CONFIG_AUTH_STORE", usernames and passwords for authentication and scopes for authorization would be read from a config toml file.
A user can specify AuthProvider
as follows and set it to the hubListenerConfig
record passed when starting the hub.
http:AuthProvider basicAuthProvider = {
scheme: http:BASIC_AUTH,
authStoreProvider: http:CONFIG_AUTH_STORE
};
http:ServiceEndpointConfiguration hubListenerConfig = {
authProviders: [basicAuthProvider],
secureSocket: {
keyStore: {
path: "${ballerina.home}/bre/security/ballerinaKeystore.p12",
password: "ballerina"
}
}
};
var val = websub:startHub(new http:Listener (9191, config = hubListenerConfig));
In addition to the AuthProvider
for listener, a user also has to specify the authConfig
properties at service
config level.
It can be populated by providing authConfig
via a toml formatted file under the b7a.websub.hub.auth
alias.
Recognized users can also be mentioned in the same file which permits auth providers to read.
["b7a.websub.hub.auth"]
enabled=true // enables the authentication
scopes="scope1" // defines the scope of possible users
["b7a.users"]
["b7a.users.tom"]
password="1234"
scopes="scope1"
Once the hub is secured over basic auth, a subscriber should provide the relevant auth
config in the
subscriptionClientConfig
field of the subscriber service annotation.
@websub:SubscriberServiceConfig {
path: "/ordereventsubscriber",
subscriptionClientConfig: {
auth: {
scheme: http:BASIC_AUTH,
username: "tom",
password: "1234"
}
}
}
Enabling data persistence for the hub
The Ballerina WebSub Hub supports persistence of topic and subscription data that needs to be restored when the hub is restarted.
Users can introduce their own persistence implementation, by introducing an object type that is structurally
equivalent to the websub:HubPersistenceStore
abstract object. Alternatively, the H2-based
websub:H2HubPersistenceStore
object made available in the ballerina/websub
module could be used to persist data.
Persistence can be enabled by setting a suitable websub:HubPersistenceStore
value for the hubPersistenceStore
field
in the HubConfiguration
record, which is passed to the websub:startHub()
function.
import ballerina/h2;
import ballerina/http;
import ballerina/websub;
// Define an `h2:Client` to use with the `websub:H2HubPersistenceStore`.
h2:Client h2Client = new({
path: "./target/hubDB",
name: "hubdb",
username: "user1",
password: "pass1"
});
// Define a `websub:H2HubPersistenceStore` as a `websub:HubPersistenceStore`.
websub:HubPersistenceStore hubPersistenceStore = new websub:H2HubPersistenceStore(h2Client);
// Set the defined persistence store as the `hubPersistenceStore` in the `hubConfig` record.
websub:HubConfiguration hubConfig = {
hubPersistenceStore: hubPersistenceStore
};
// Pass the `hubConfig` record when starting up the hub to enable persistence.
var result = websub:startHub(new http:Listener(8080), hubConfiguration = hubConfig);
Any subscriptions added at the hub will now be available even when the hub is restarted.
Publisher
Ballerina WebSub publishers can use utility functions to add WebSub link headers indicating the hub and topic URLs, which facilitates WebSub discovery.
A hub client endpoint is also made available to publishers and subscribers to perform the following:
- Publishers
- Register a topic at the Hub
- Publish to the hub indicating an update of the topic
- Subscribers
- Subscribe/Unsubscribe to/from topics at a hub
Samples
This sample demonstrates a Subscriber Service with subscribeOnStartUp
set to true. This will result in a
subscription request being sent to the specified hub for the specified topic, with the specified lease seconds value
and the specified secret for authenticated content distribution.
Since an onIntentVerification
resource function is not included, intent verification for subscription and unsubscription
requests would happen automatically, if the topic specified in the request matches that specified as an annotation or
that discovered for the annotated resource URL.
import ballerina/log;
import ballerina/websub;
listener websub:Listener websubEP = new(8181);
@websub:SubscriberServiceConfig {
path: "/websub",
subscribeOnStartUp: true,
topic: "<TOPIC_URL>",
hub: "<HUB_URL>",
leaseSeconds: 3600,
secret: "<SECRET>"
}
service websubSubscriber on websubEP {
resource function onNotification(websub:Notification notification) {
var payload = notification.getTextPayload();
if (payload is string) {
log:printInfo("WebSub Notification Received: " + payload);
} else {
log:printError("Error retrieving payload as string", err = payload);
}
}
}
Explicit intent verification can be done by introducing an onIntentVerification
resource function.
import ballerina/http;
import ballerina/log;
import ballerina/websub;
listener websub:Listener websubEP = new(8181);
@websub:SubscriberServiceConfig {
path: "/websub",
subscribeOnStartUp: true,
topic: "<TOPIC_URL>",
hub: "<HUB_URL>",
leaseSeconds: 3600,
secret: "<SECRET>"
}
service websubSubscriber on websubEP {
resource function onIntentVerification(websub:Caller caller, websub:IntentVerificationRequest request) {
http:Response response = new;
// Insert logic to build subscription/unsubscription intent verification response.
var result = caller->respond(response);
if (result is error) {
log:printError("Error responding to intent verification request", err = result);
}
}
resource function onNotification(websub:Notification notification) {
var payload = notification.getTextPayload();
if (payload is string) {
log:printInfo("WebSub Notification Received: " + payload);
} else {
log:printError("Error retrieving payload as string", err = payload);
}
}
}
Functions are made available on the websub:IntentVerificationRequest
to build a subscription or unsubscription
verification response, specifying the topic to verify intent against:
http:Response response = request.buildSubscriptionVerificationResponse("<TOPIC_TO_VERIFY_FOR>");
http:Response response = request.buildUnsubscriptionVerificationResponse("<TOPIC_TO_VERIFY_FOR>");
Ballerina publishers can start up and publish directly to the Ballerina WebSub hub.
import ballerina/log;
import ballerina/http;
import ballerina/runtime;
import ballerina/websub;
public function main() {
log:printInfo("Starting up the Ballerina Hub Service");
var result = websub:startHub(new http:Listener(9191));
websub:WebSubHub webSubHub = result is websub:WebSubHub ? result : result.startedUpHub;
var registrationResponse = webSubHub.registerTopic("<TOPIC_URL>");
if (registrationResponse is error) {
log:printError("Error occurred registering topic: " + <string>registrationResponse.detail().message);
} else {
log:printInfo("Topic registration successful!");
}
// Make the publisher wait until the subscriber subscribes at the hub.
runtime:sleep(20000);
log:printInfo("Publishing update to internal Hub");
var publishResponse = webSubHub.publishUpdate("<TOPIC_URL>", {"action": "publish", "mode": "internal-hub"});
if (publishResponse is error) {
log:printError("Error notifying hub: " + <string>publishResponse.detail().message);
} else {
log:printInfo("Update notification successful!");
}
// Make sure the service is running until the subscriber receives the update notification.
runtime:sleep(5000);
}
Ballerina publishers can also use the hub client endpoint to register topics at Ballerina WebSub hubs and publish/notify updates to the remote hubs.
import ballerina/log;
import ballerina/runtime;
import ballerina/websub;
websub:Client websubHubClientEP = new("https://localhost:9191/websub/hub");
public function main() {
var registrationResponse = websubHubClientEP->registerTopic("<TOPIC_URL>");
if (registrationResponse is error) {
log:printError("Error occurred registering topic: " + <string>registrationResponse.detail().message);
} else {
log:printInfo("Topic registration successful!");
}
// Make the publisher wait until the subscriber subscribes at the hub.
runtime:sleep(10000);
log:printInfo("Publishing update to remote Hub");
var publishResponse = websubHubClientEP->publishUpdate("<TOPIC_URL>", { "action": "publish", "mode": "remote-hub" });
if (publishResponse is error) {
log:printError("Error notifying hub: " + <string>publishResponse.detail().message);
} else {
log:printInfo("Update notification successful!");
}
}
The hub client endpoint can also be used by subscribers to send subscription and unsubscription requests explicitly.
import ballerina/log;
import ballerina/websub;
websub:Client websubHubClientEP = new("<HUB_URL>");
public function main() {
// Send subscription request for a subscriber service.
websub:SubscriptionChangeRequest subscriptionRequest = {
topic: "<TOPIC_URL>",
callback: "<CALLBACK_URL>",
secret: "<SECRET>"
};
var subscriptionChangeResponse = websubHubClientEP->subscribe(subscriptionRequest);
if (subscriptionChangeResponse is websub:SubscriptionChangeResponse) {
log:printInfo("Subscription Request successful at Hub [" + subscriptionChangeResponse.hub
+ "] for Topic [" + subscriptionChangeResponse.topic + "]");
} else {
log:printError("Error occurred with Subscription Request", err = subscriptionChangeResponse);
}
// Send unsubscription request for the subscriber service.
websub:SubscriptionChangeRequest unsubscriptionRequest = {
topic: "<TOPIC_URL>",
callback: "<CALLBACK_URL>"
};
subscriptionChangeResponse = websubHubClientEP->unsubscribe(unsubscriptionRequest);
if (subscriptionChangeResponse is websub:SubscriptionChangeResponse) {
log:printInfo("Unsubscription Request successful at Hub [" + subscriptionChangeResponse.hub
+ "] for Topic [" + subscriptionChangeResponse.topic + "]");
} else {
log:printError("Error occurred with Unsubscription Request", err = subscriptionChangeResponse);
}
}
Configuration Parameters
The Ballerina WebSub implementation allows specifying the following properties/parameters via the Ballerina Config API, where the values specified via the Config API would override values specified as params on hub start up.
Configuration Key | Default Value | Description |
---|---|---|
b7a.websub.hub.leasetime | 86400 | The default lease period, if not specified in a request |
b7a.websub.hub.signaturemethod | "SHA256" | The signature method to use for authenticated content distribution |
b7a.websub.hub.remotepublish | false | Whether publishing updates against the topics in the hub could be done by remote publishers via HTTP requests with hub.mode set to publish |
b7a.websub.hub.topicregistration | true | Whether a topic needs to be registered at the hub for publishers to publish updates against the topic and for subscribers to send subscription requests for the topic |
Introducing Specific Subscriber Services (Webhook Callback Services)
Ballerina's WebSub subscriber service listener can be extended to introduce specific Webhooks.
Instead of the single onNotification
resource, you can introduce multiple resources to accept content delivery requests using specific subscriber services. These resources will correspond to the content delivery requests that will
be delivered with respect to a particular topic.
For example, assume a scenario in which you receive notifications either when an issue is opened or when an issue is closed by subscribing to a particular topic in an issue tracking system. With a custom subscriber service listener, which extends the
generic WebSub subscriber service listener, you can allow two resources to accept content delivery requests (e.g., onIssueOpened
and onIssueClosed
) instead of the onNotification
resource.
These resources will accept two parameters:
- The generic
websub:Notification
record as the first parameter - A custom record corresponding to the expected (JSON) payload of the notification (e.g.,
IssueCreatedEvent
,IssueClosedEvent
)
You can introduce a specific service as such by extending the generic subscriber service listener, specifying a mapping between the expected notifications and the resources that requests need to be dispatched to.
The mapping can be based on one of the following indicators of a notification request. (Requests will then be dispatched based on the value of the indicator in the request and a pre-defined mapping.)
- A request header
- The payload: the value of a particular key in the JSON payload
- A request header and the payload (combination of the above two)
Samples for Resource Mapping
Based on a request header
Dispatching will be based on the value of the request header specified as topicHeader
.
websub:ExtensionConfig extensionConfig = {
topicIdentifier: websub:TOPIC_ID_HEADER,
topicHeader: "<HEADER_TO_CONSIDER>",
headerResourceMap: {
"issueOpened": ("onIssueOpened", IssueOpenedEvent),
"issueClosed": ("onIssueClosed", IssueClosedEvent)
}
};
The "issueOpened": ("onIssueOpened", IssueOpenedEvent)
entry indicates that when the value of the
<HEADER_TO_CONSIDER>
header is issueOpened
, dispatching should happen to a resource named onIssueOpened
.
The first parameter of this resource will be the generic websub:Notification
record, and the second parameter will
be a custom IssueOpenedEvent
record mapping the JSON payload received when an issue is created.
Based on the payload
Dispatching will be based on the value in the request payload of one of the map keys specified in the
payloadKeyResourceMap
map.
websub:ExtensionConfig extensionConfig = {
topicIdentifier: websub:TOPIC_ID_PAYLOAD_KEY,
payloadKeyResourceMap: {
"<PAYLOAD_KEY_TO_CONSIDER>": {
"issueOpened": ("onIssueOpened", IssueOpenedEvent),
"issueClosed": ("onIssueClosed", IssueClosedEvent)
}
}
};
The "issueOpened": ("onIssueOpened", IssueOpenedEvent)
entry indicates that when the value for the JSON payload
key <PAYLOAD_KEY_TO_CONSIDER>
is issueOpened
, dispatching should happen to a resource named onIssueOpened
.
The first parameter of this resource will be the generic websub:Notification
record, and the second parameter will
be a custom IssueOpenedEvent
record, mapping the JSON payload received when an issue is created.
Based on a request header and the payload
Dispatching will be based on both a request header and the payload as specified in the headerAndPayloadKeyResourceMap
.
Also, you can introduce a headerResourceMap
and/or a payloadKeyResourceMap
as additional mappings.
websub:ExtensionConfig extensionConfig = {
topicIdentifier: websub:TOPIC_ID_HEADER_AND_PAYLOAD,
topicHeader: "<HEADER_TO_CONSIDER>",
headerAndPayloadKeyResourceMap: {
"issue" : {
"<PAYLOAD_KEY_TO_CONSIDER>" : {
"opened": ("onIssueOpened", IssueOpenedEvent),
"closed": ("onIssueClosed", IssueClosedEvent)
}
}
}
};
The "opened": ("onIssueOpened", IssueOpenedEvent)
entry indicates that when the value of the
<HEADER_TO_CONSIDER>
header is issue
and the value of the <PAYLOAD_KEY_TO_CONSIDER>
JSON payload key is opened
,
dispatching should happen to a resource named onIssueOpened
.
The first parameter of this resource will be the generic websub:Notification
record and the second parameter will
be a custom IssueOpenedEvent
record, mapping the JSON payload received when an issue is created.
Sample Specific Subscriber Service
In order to introduce a specific subscriber service, a new Ballerina listener
needs to be introduced. This listener
should wrap the generic ballerina/websub:Listener
and include the extension configuration described above.
The following example is for a service provider that
- allows registering webhooks to receive notifications when an issue is opened or assigned
- includes a header named "Event-Header" in each content delivery request indicating what event the notification is for (e.g., "onIssueOpened" when an issue is opened and "onIssueAssigned" when an issue is assigned)
import ballerina/websub;
// Introduce a record mapping the JSON payload received when an issue is opened.
public type IssueOpenedEvent record {
int id;
string title;
string openedBy;
};
// Introduce a record mapping the JSON payload received when an issue is assigned.
public type IssueAssignedEvent record {
int id;
string assignedTo;
};
// Introduce a new `listener` wrapping the generic `ballerina/websub:Listener`
public type WebhookListener object {
*AbstractListener;
private websub:Listener websubListener;
public function __init(int port) {
// Introduce the extension config, based on the mapping details.
websub:ExtensionConfig extensionConfig = {
topicIdentifier: websub:TOPIC_ID_HEADER,
topicHeader: "Event-Header",
headerResourceMap: {
"issueOpened": ("onIssueOpened", IssueOpenedEvent),
"issueAssigned": ("onIssueAssigned", IssueAssignedEvent)
}
};
// Set the extension config in the generic `websub:Listener` config.
websub:SubscriberServiceEndpointConfiguration sseConfig = {
extensionConfig: extensionConfig
};
// Initialize the wrapped generic listener.
self.websubListener = new(port, config = sseConfig);
}
public function __attach(service s, string? name = ()) returns error? {
return self.websubListener.__attach(s, name = name);
}
public function __start() returns error? {
return self.websubListener.__start();
}
public function __stop() returns error? {
return self.websubListener.__stop();
}
};
A service can now be introduced for the above service provider as follows.
import ballerina/io;
import ballerina/log;
import ballerina/websub;
@websub:SubscriberServiceConfig {
path: "/subscriber",
subscribeOnStartUp: false
}
service specificSubscriber on new WebhookListener(8080) {
resource function onIssueOpened(websub:Notification notification, IssueOpenedEvent issueOpened) {
log:printInfo(io:sprintf("Issue opened: ID: %s, Title: %s", issueOpened.id, issueOpened.title));
}
resource function onIssueAssigned(websub:Notification notification, IssueAssignedEvent issueAssigned) {
log:printInfo(io:sprintf("Issue ID %s assigned to %s", issueAssigned.id, issueAssigned.assignedTo));
}
}
For a step-by-step guide on introducing custom subscriber services, see the "Create Webhook Callback Services" section of "How to Extend Ballerina".
Type Definitions
Type | Values | Description | |
---|---|---|---|
RemotePublishMode | PUBLISH_MODE_FETCH | PUBLISH_MODE_DIRECT | The identifier to be used to identify the mode in which update content should be identified. |
|
SignatureMethod | SHA256 | SHA1 | The identifier to be used to identify the cryptographic hash algorithm. |
|
TopicIdentifier | TOPIC_ID_PAYLOAD_KEY | TOPIC_ID_HEADER_AND_PAYLOAD | TOPIC_ID_HEADER | The identifier to be used to identify the topic for dispatching with custom subscriber services. |
Annotations
Name | Attachement Points | Data Type | Description |
---|---|---|---|
SubscriberServiceConfig | service | SubscriberServiceConfiguration | WebSub Subscriber Configuration for the service, indicating subscription related parameters. |
Records Summary
Record | Description | ||
---|---|---|---|
ExtensionConfig | The extension configuration to introduce custom subscriber services. | ||
HubConfiguration | Record representing hub specific configurations. | ||
HubStartedUpError | Error to represent that a WebSubHub is already started up, encapsulating the started up Hub. | ||
RemotePublishConfig | Record representing remote publishing allowance. | ||
SubscriberDetails | Record to represent Subscriber Details. | ||
SubscriberServiceConfiguration | Configuration for a WebSubSubscriber service. | ||
SubscriberServiceEndpointConfiguration | Object representing the configuration for the WebSub Subscriber Service Endpoint. | ||
SubscriptionChangeRequest | Record representing a WebSub subscription change request. | ||
SubscriptionChangeResponse | Record representing subscription/unsubscription details if a subscription/unsubscription request is successful. | ||
SubscriptionDetails | Record to represent persisted Subscription Details retrieved. |
Objects Summary
Object | Description | ||
---|---|---|---|
H2HubPersistenceStore | Represents H2 based hub persistence configuration and functions. |
||
HubPersistenceStore | Represents the hub persistence configuration and functions. |
||
IntentVerificationRequest | Object representing an intent verification request received. |
||
Listener | Object representing the WebSubSubscriber Service Endpoint. |
||
Notification | Object representing the WebSub Content Delivery Request received. |
||
WebSubHub | Object representing a Ballerina WebSub Hub. |
Endpoints Summary
Endpoint | Description | ||
---|---|---|---|
Caller | The caller remote functions to respond to client requests. |
||
Client | The HTTP based Caller remote functions for outbound WebSub Subscription, Unsubscription, Registration, Unregistration and Notification requests to a Hub. |
Functions Summary
Return Type | Function and Description | ||
---|---|---|---|
addWebSubLinkHeader(http:Response response, string[] hubs, string topic) Function to add link headers to a response to allow WebSub discovery. |
|||
(string,string[])|error<> | extractTopicAndHubUrls(http:Response response) Function to retrieve hub and topic URLs from the |
||
WebSubHub|HubStartedUpError | startHub(http:Listener hubServiceListener, websub:HubConfiguration? hubConfiguration) Starts up the Ballerina Hub. |
Constants
Name | Data Type | Value | Description | |
---|---|---|---|---|
WEBSUB_ERROR_CODE | string | {ballerina/websub}WebSubError | The constant used to represent error code of WebSub module. |
|
PUBLISH_MODE_DIRECT | PUBLISH_MODE_DIRECT |
|
||
PUBLISH_MODE_FETCH | PUBLISH_MODE_FETCH |
|
||
SHA1 | string | SHA1 | The constant used to represent SHA-1 cryptographic hash algorithm |
|
SHA256 | string | SHA256 | The constant used to represent SHA-256 cryptographic hash algorithm |
|
TOPIC_ID_HEADER | TOPIC_ID_HEADER |
|
||
TOPIC_ID_PAYLOAD_KEY | TOPIC_ID_PAYLOAD_KEY |
|
||
TOPIC_ID_HEADER_AND_PAYLOAD | TOPIC_ID_HEADER_AND_PAYLOAD |
|
public type ExtensionConfig record
The extension configuration to introduce custom subscriber services.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
topicIdentifier | TOPIC_ID_HEADER|TOPIC_ID_PAYLOAD_KEY|TOPIC_ID_HEADER_AND_PAYLOAD | TOPIC_ID_HEADER | The identifier based on which dispatching should happen for custom subscriber |
topicHeader | string? | () | The header to consider if required with dispatching for custom services |
headerResourceMap | map<(string,typedesc)>? | () | The mapping between header value and resource details |
payloadKeyResourceMap | map | () | The mapping between value for a particular JSON payload key and resource details |
headerAndPayloadKeyResourceMap | map | () | The mapping between values for the header and a particular JSON payload key and resource details |
public type HubConfiguration record
Record representing hub specific configurations.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
leaseSeconds | int | 86400 | The default lease seconds value to honour if not specified in subscription requests |
signatureMethod | SHA1|SHA256 | SHA256 | The signature method to use for authenticated content delivery ( |
remotePublish | websub:RemotePublishConfig | The record representing configuration related to remote publishing allowance |
|
topicRegistrationRequired | boolean | true | Whether a topic needs to be registered at the hub prior to publishing/subscribing to the topic |
publicUrl | string | The URL for the hub to be included in content delivery requests, defaults to
|
|
clientConfig | http:ClientEndpointConfig | The configuration for the hub to communicate with remote HTTP endpoints |
|
hubPersistenceStore | websub:HubPersistenceStore | The |
public type HubStartedUpError record
Error to represent that a WebSubHub is already started up, encapsulating the started up Hub.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
message | string | The error message |
|
cause | error? | () | The cause of the |
startedUpHub | websub:WebSubHub | The |
public type RemotePublishConfig record
Record representing remote publishing allowance.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
enabled | boolean | false | Whether remote publishers should be allowed to publish to this hub (HTTP requests) |
mode | PUBLISH_MODE_DIRECT|PUBLISH_MODE_FETCH | PUBLISH_MODE_DIRECT | If remote publishing is allowed, the mode to use, |
public type SubscriberDetails record
Record to represent Subscriber Details.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
callback | string | The callback specified for the particular subscription |
|
leaseSeconds | int | 0 | The lease second period specified for the particular subscription |
createdAt | int | 0 | The time at which the subscription was created |
public type SubscriberServiceConfiguration record
Configuration for a WebSubSubscriber service.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
endpoints | websub:Listener?[] | [] | Array of endpoints the service would be attached to |
path | string | Path of the WebSubSubscriber service |
|
subscribeOnStartUp | boolean | false | Boolean indicating whether a subscription request is expected to be sent on start up |
resourceUrl | string | The resource URL for which discovery will be initiated to identify hub and topic if not specified |
|
hub | string | The hub at which the subscription should be registered |
|
topic | string | The topic for which this WebSub subscriber (callback) should be registered |
|
leaseSeconds | int | 0 | The period for which the subscription is expected to be active |
secret | string | The secret to be used for authenticated content distribution |
|
callback | string | The callback to use when registering, if unspecified host:port/path will be used |
|
subscriptionClientConfig | http:ClientEndpointConfig | The configuration for subscription client |
public type SubscriberServiceEndpointConfiguration record
Object representing the configuration for the WebSub Subscriber Service Endpoint.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
host | string | The host name/IP of the endpoint |
|
httpServiceSecureSocket | http:ServiceSecureSocket? | () | The SSL configurations for the service endpoint |
extensionConfig | websub:ExtensionConfig? | () | The extension configuration to introduce custom subscriber services (webhooks) |
public type SubscriptionChangeRequest record
Record representing a WebSub subscription change request.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
topic | string | The topic for which the subscription/unsubscription request is sent |
|
callback | string | The callback which should be registered/unregistered for the subscription/unsubscription request sent |
|
leaseSeconds | int | 0 | The lease period for which the subscription is expected to be active |
secret | string | The secret to be used for authenticated content distribution with this subscription |
public type SubscriptionChangeResponse record
Record representing subscription/unsubscription details if a subscription/unsubscription request is successful.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
hub | string | The hub at which the subscription/unsubscription was successful |
|
topic | string | The topic for which the subscription/unsubscription was successful |
|
response | http:Response | The response from the hub to the subscription/unsubscription request |
public type SubscriptionDetails record
Record to represent persisted Subscription Details retrieved.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
topic | string | The topic for which the subscription is added |
|
callback | string | The callback specified for the particular subscription |
|
secret | string | The secret to be used for authenticated content distribution |
|
leaseSeconds | int | 0 | The lease second period specified for the particular subscription |
createdAt | int | 0 | The time at which the subscription was created |
public function addWebSubLinkHeader(http:Response response, string[] hubs, string topic)
Function to add link headers to a response to allow WebSub discovery.
Parameter Name | Data Type | Default Value | Description |
---|---|---|---|
response | http:Response | The response being sent |
|
hubs | string[] | The hubs the publisher advertises as the hubs that it publishes updates to |
|
topic | string | The topic to which subscribers need to subscribe to, to receive updates for the resource |
public function extractTopicAndHubUrls(http:Response response) returns ((string,string[])|error<>)
Function to retrieve hub and topic URLs from the http:response
from a publisher to a discovery request.
Parameter Name | Data Type | Default Value | Description |
---|---|---|---|
response | http:Response | The |
Return Type | Description | ||
---|---|---|---|
(string,string[])|error<> |
|
public function startHub(http:Listener hubServiceListener, websub:HubConfiguration? hubConfiguration) returns (WebSubHub|HubStartedUpError)
Starts up the Ballerina Hub.
Parameter Name | Data Type | Default Value | Description |
---|---|---|---|
hubServiceListener | http:Listener | The |
|
hubConfiguration | websub:HubConfiguration? | () | The hub specific configuration |
Return Type | Description | ||
---|---|---|---|
WebSubHub|HubStartedUpError |
|
public type H2HubPersistenceStore object
Represents H2 based hub persistence configuration and functions.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
subscriptionDbClient | h2:Client | Database clint used to persist subscription data |
-
<H2HubPersistenceStore> __init(h2:Client subscriptionDbClient)
Parameter Name Data Type Default Value Description subscriptionDbClient h2:Client -
<H2HubPersistenceStore> addSubscription(websub:SubscriptionDetails subscriptionDetails)
Function to add or update subscription details.
Parameter Name Data Type Default Value Description subscriptionDetails websub:SubscriptionDetails The details of the subscription to add or update
-
<H2HubPersistenceStore> removeSubscription(websub:SubscriptionDetails subscriptionDetails)
Function to remove subscription details.
Parameter Name Data Type Default Value Description subscriptionDetails websub:SubscriptionDetails The details of the subscription to remove
-
<H2HubPersistenceStore> addTopic(string topic)
Function to add a topic.
Parameter Name Data Type Default Value Description topic string The topic to add
-
<H2HubPersistenceStore> removeTopic(string topic)
Function to remove a topic.
Parameter Name Data Type Default Value Description topic string The topic to remove
-
<H2HubPersistenceStore> retrieveTopics() returns (string[])
Function to retrieve all registered topics.
Return Type Description string[] An array of topics
-
<H2HubPersistenceStore> retrieveAllSubscribers() returns (SubscriptionDetails[])
Function to retrieve subscription details of all subscribers.
Return Type Description SubscriptionDetails[] An array of subscriber details
public type HubPersistenceStore object
Represents the hub persistence configuration and functions.
-
<HubPersistenceStore> addSubscription(websub:SubscriptionDetails subscriptionDetails)
Function to add or update subscription details.
Parameter Name Data Type Default Value Description subscriptionDetails websub:SubscriptionDetails The details of the subscription to add or update
-
<HubPersistenceStore> removeSubscription(websub:SubscriptionDetails subscriptionDetails)
Function to remove subscription details.
Parameter Name Data Type Default Value Description subscriptionDetails websub:SubscriptionDetails The details of the subscription to remove
-
<HubPersistenceStore> addTopic(string topic)
Function to add a topic.
Parameter Name Data Type Default Value Description topic string The topic to add
-
<HubPersistenceStore> removeTopic(string topic)
Function to remove a topic.
Parameter Name Data Type Default Value Description topic string The topic to remove
-
<HubPersistenceStore> retrieveTopics() returns (string[])
Function to retrieve all registered topics.
Return Type Description string[] An array of topics
-
<HubPersistenceStore> retrieveAllSubscribers() returns (SubscriptionDetails[])
Function to retrieve subscription details of all subscribers.
Return Type Description SubscriptionDetails[] An array of subscriber details
public type IntentVerificationRequest object
Object representing an intent verification request received.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
mode | string | The mode specified in the intent verification request, subscription or unsubscription |
|
topic | string | The topic for which intent is verified to subscribe/unsubscribe |
|
challenge | string | The challenge to be echoed to verify intent to subscribe/unsubscribe |
|
leaseSeconds | int | 0 | The lease seconds period for which a subscription will be active if intent verification is being done for subscription |
request | http:Request | BLangTypeInit: new null ([]) | The HTTP request received for intent verification |
-
<IntentVerificationRequest> buildSubscriptionVerificationResponse(string expectedTopic) returns (Response)
Builds the response for the request, verifying intention to subscribe, if the topic matches that expected.
Parameter Name Data Type Default Value Description expectedTopic string The topic for which subscription should be accepted
Return Type Description Response http:Response
The response to the hub verifying/denying intent to subscribe -
<IntentVerificationRequest> buildUnsubscriptionVerificationResponse(string expectedTopic) returns (Response)
Builds the response for the request, verifying intention to unsubscribe, if the topic matches that expected.
Parameter Name Data Type Default Value Description expectedTopic string The topic for which unsubscription should be accepted
Return Type Description Response http:Response
The response to the hub verifying/denying intent to unsubscribe
public type Listener object
Object representing the WebSubSubscriber Service Endpoint.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
config | websub:SubscriberServiceEndpointConfiguration? | () | The configuration for the endpoint |
-
<Listener> __init(int port, websub:SubscriberServiceEndpointConfiguration? config)
Parameter Name Data Type Default Value Description port int config websub:SubscriberServiceEndpointConfiguration? () -
<Listener> __attach(service s, string? name) returns (error<>|null)
Parameter Name Data Type Default Value Description s service name string? () Return Type Description error<>|null
public type Notification object
Object representing the WebSub Content Delivery Request received.
-
<Notification> getQueryParams() returns (map<string>)
Retrieves the query parameters of the content delivery request, as a map.
Return Type Description map String constrained map of query params
-
<Notification> getEntity() returns (mime:Entity|error<>)
Retrieves the
Entity
associated with the content delivery request.Return Type Description mime:Entity|error<> The
Entity
of the request. Anerror
is returned, if entity construction fails -
<Notification> hasHeader(string headerName) returns (boolean)
Returns whether the requested header key exists in the header map of the content delivery request.
Parameter Name Data Type Default Value Description headerName string The header name
Return Type Description boolean Returns true if the specified header key exists
-
<Notification> getHeader(string headerName) returns (string)
Returns the value of the specified header. If the specified header key maps to multiple values, the first of these values is returned.
Parameter Name Data Type Default Value Description headerName string The header name
Return Type Description string The first header value for the specified header name. An exception is thrown if no header is found. Ideally
hasHeader()
needs to be used to check the existence of header initially. -
<Notification> getHeaders(string headerName) returns (string[])
Retrieves all the header values to which the specified header key maps to.
Parameter Name Data Type Default Value Description headerName string The header name
Return Type Description string[] The header values the specified header key maps to. An exception is thrown if no header is found. Ideally
hasHeader()
needs to be used to check the existence of header initially. -
<Notification> getHeaderNames() returns (string[])
Retrieves all the names of the headers present in the content delivery request.
Return Type Description string[] An array of all the header names
-
<Notification> getContentType() returns (string)
Retrieves the type of the payload of the content delivery request (i.e: the
content-type
header value).Return Type Description string Returns the
content-type
header value as a string -
<Notification> getJsonPayload() returns (json|error<>)
Extracts
json
payload from the content delivery request.Return Type Description json|error<> The
json
payload orerror
in case of errors. If the content type is not JSON, anerror
is returned. -
<Notification> getXmlPayload() returns (xml|error<>)
Extracts
xml
payload from the content delivery request.Return Type Description xml|error<> The
xml
payload orerror
in case of errors. If the content type is not XML, anerror
is returned. -
<Notification> getTextPayload() returns (string|error<>)
Extracts
text
payload from the content delivery request.Return Type Description string|error<> The
text
payload orerror
in case of errors. If the content type is not of type text, anerror
is returned. -
<Notification> getByteChannel() returns (io:ReadableByteChannel|error<>)
Retrieves the request payload as a
ByteChannel
except in the case of multiparts.Return Type Description io:ReadableByteChannel|error<> A byte channel from which the message payload can be read or
error
in case of errors -
<Notification> getBinaryPayload() returns (byte[]|error<>)
Retrieves the request payload as a
byte[]
.Return Type Description byte[]|error<> The byte[] representation of the message payload or
error
in case of errors -
<Notification> getFormParams() returns (map<string>|error<>)
Retrieves the form parameters from the content delivery request as a
map
.Return Type Description map |error<> The map of form params or
error
in case of errors
public type WebSubHub object
Object representing a Ballerina WebSub Hub.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
hubUrl | string | The URL of the started up Ballerina WebSub Hub |
-
<WebSubHub> __init(string hubUrl, http:Listener hubHttpListener)
Parameter Name Data Type Default Value Description hubUrl string hubHttpListener http:Listener -
<WebSubHub> stop() returns (boolean)
Stops the started up Ballerina WebSub Hub.
Return Type Description boolean boolean
indicating whether the internal Ballerina Hub was stopped -
<WebSubHub> publishUpdate(string topic, string|xml|json|byte[]|io:ReadableByteChannel payload, string? contentType) returns (error<>|null)
Publishes an update against the topic in the initialized Ballerina Hub.
Parameter Name Data Type Default Value Description topic string The topic for which the update should happen
payload string|xml|json|byte[]|io:ReadableByteChannel The update payload
contentType string? () The content type header to set for the request delivering the payload
Return Type Description error<>|null error
if the hub is not initialized or does not represent the internal hub -
<WebSubHub> registerTopic(string topic) returns (error<>|null)
Registers a topic in the Ballerina Hub.
Parameter Name Data Type Default Value Description topic string The topic to register
Return Type Description error<>|null error
if an error occurred with registration -
<WebSubHub> unregisterTopic(string topic) returns (error<>|null)
Unregisters a topic in the Ballerina Hub.
Parameter Name Data Type Default Value Description topic string The topic to unregister
Return Type Description error<>|null error
if an error occurred with unregistration -
<WebSubHub> getAvailableTopics() returns (string[])
Retrieves topics currently recognized by the Hub.
Return Type Description string[] An array of available topics
-
<WebSubHub> getSubscribers(string topic) returns (SubscriberDetails[])
Retrieves details of subscribers registered to receive updates for a particular topic.
Parameter Name Data Type Default Value Description topic string The topic for which details need to be retrieved
Return Type Description SubscriberDetails[] An array of subscriber details
Endpoint Caller
The caller remote functions to respond to client requests.
-
<Caller> respond(http:Response|string|xml|json|byte[]|io:ReadableByteChannel|mime:Entity[] message) returns (error<>|null)
Sends the response to the caller.
Parameter Name Data Type Default Value Description message http:Response|string|xml|json|byte[]|io:ReadableByteChannel|mime:Entity[] The response or any payload of type
string
,xml
,json
,byte[]
,io:ReadableByteChannel
ormime:Entity[]
Return Type Description error<>|null Returns an
error
on failure -
<Caller> ok(http:Response|string|xml|json|byte[]|io:ReadableByteChannel|mime:Entity[] message) returns (error<>|null)
Sends the response to the caller with the status 200 OK.
Parameter Name Data Type Default Value Description message http:Response|string|xml|json|byte[]|io:ReadableByteChannel|mime:Entity[] The response or any payload of type
string
,xml
,json
,byte[]
,io:ReadableByteChannel
ormime:Entity[]
Return Type Description error<>|null Returns an
error
on failure -
<Caller> accepted(http:Response|string|xml|json|byte[]|io:ReadableByteChannel|mime:Entity[] message) returns (error<>|null)
Sends the response to the caller with the status 202 Accepted.
Parameter Name Data Type Default Value Description message http:Response|string|xml|json|byte[]|io:ReadableByteChannel|mime:Entity[] () The response or any payload of type
string
,xml
,json
,byte[]
,io:ReadableByteChannel
ormime:Entity[]
. This message is optional.Return Type Description error<>|null Returns an
error
on failure
Endpoint Client
The HTTP based Caller remote functions for outbound WebSub Subscription, Unsubscription, Registration, Unregistration and Notification requests to a Hub.
Field Name | Data Type | Default Value | Description |
---|---|---|---|
hubUrl | string | The URL of the target Hub to which requests need to be sent |
-
<Client> subscribe(websub:SubscriptionChangeRequest subscriptionRequest) returns (SubscriptionChangeResponse|error<>)
Sends a subscription request to a WebSub Hub.
Parameter Name Data Type Default Value Description subscriptionRequest websub:SubscriptionChangeRequest The
SubscriptionChangeRequest
containing subscription detailsReturn Type Description SubscriptionChangeResponse|error<> SubscriptionChangeResponse
indicating subscription details, if the request was successful elseerror
if an error occurred with the subscription request -
<Client> unsubscribe(websub:SubscriptionChangeRequest unsubscriptionRequest) returns (SubscriptionChangeResponse|error<>)
Sends an unsubscription request to a WebSub Hub.
Parameter Name Data Type Default Value Description unsubscriptionRequest websub:SubscriptionChangeRequest The
SubscriptionChangeRequest
containing unsubscription detailsReturn Type Description SubscriptionChangeResponse|error<> SubscriptionChangeResponse
indicating unsubscription details, if the request was successful elseerror
if an error occurred with the unsubscription request -
<Client> registerTopic(string topic) returns (error<>|null)
Registers a topic in a Ballerina WebSub Hub against which subscribers can subscribe and the publisher will publish updates.
Parameter Name Data Type Default Value Description topic string The topic to register
Return Type Description error<>|null error
if an error occurred registering the topic -
<Client> unregisterTopic(string topic) returns (error<>|null)
Unregisters a topic in a Ballerina WebSub Hub.
Parameter Name Data Type Default Value Description topic string The topic to unregister
Return Type Description error<>|null error
if an error occurred unregistering the topic -
<Client> publishUpdate(string topic, string|xml|json|byte[]|io:ReadableByteChannel payload, string? contentType, map<string>? headers) returns (error<>|null)
Publishes an update to a remote Ballerina WebSub Hub.
Parameter Name Data Type Default Value Description topic string The topic for which the update occurred
payload string|xml|json|byte[]|io:ReadableByteChannel The update payload
contentType string? () The type of the update content, to set as the
ContentType
headerheaders map ? () The headers, if any, that need to be set
Return Type Description error<>|null error
if an error occurred with the update -
<Client> notifyUpdate(string topic, map<string>? headers) returns (error<>|null)
Notifies a remote WebSub Hub that an update is available to fetch, for hubs that require publishing to happen as such.
Parameter Name Data Type Default Value Description topic string The topic for which the update occurred
headers map ? () The headers, if any, that need to be set
Return Type Description error<>|null error
if an error occurred with the notification