// Category: debezium-using // Type: assembly [id="debezium-notification"] = {prodname} notifications ifdef::community[] :toc: :toc-placement: macro :linkattrs: :icons: font :source-highlighter: highlight.js toc::[] == Overview endif::community[] {prodname} notifications provide a mechanism to obtain status information about the connector. Notifications can be sent to the following channels: SinkNotificationChannel:: Notifications are sent through the Connect API to a configured topic. LogNotificationChannel:: Notification are appended to the log. Custom:: Notifications are sent to a xref:debezium-notification-custom-channel[custom channel] that you implement. // Type: concept [id="debezium-notification-format"] == Debezium notification format Notification messages contain the following information: |=== |Property |Description |id |A unique identifier that is assigned to the notification. For incremental snapshot notifications, the `id` is the same sent with the `execute-snapshot` signal. |aggregate_type |The data type of the aggregate root to which a notification is related. In domain-driven design, exported events should always refer to an aggregate. |type |Provides status information about the event specified in the `aggregate_type` field. |additional_data |A Map with detailed information about the notification. For an example, see xref:debezium-notifications-about-the-progress-of-incremental-snapshots[{prodname} notifications about the progress of incremental snapshots]. |=== // Type: concept [id="debezium-available-notifications"] === Available notifications {prodname} notifications deliver information about the progress of xref:debezium-notifications-about-the-status-of-an-initial-snapshot[initial snapshots] or xref:debezium-notifications-about-the-progress-of-incremental-snapshot[incremental snapshots]. ==== Status of an initial snapshot The following example shows a typical notification that provides the status of an initial snapshot: [source, json] ---- { "id": "5563ae14-49f8-4579-9641-c1bbc2d76f99", "aggregate_type": "Initial Snapshot", "type": "COMPLETED" <1> } ---- <1> The type field can contain one of the following values: * `COMPLETED` * `ABORTED` * `SKIPPED` [id="debezium-notifications-about-the-progress-of-incremental-snapshots"] ==== {prodname} notifications about the progress of incremental snapshots The following table shows examples of the different payloads that might be present in notifications that report the status of incremental snapshots: |=== |Status|Payload |Start a|[source, json] ---- { "id":"ff81ba59-15ea-42ae-b5d0-4d74f1f4038f", "aggregate_type":"Incremental Snapshot", "type":"STARTED", "additional_data":{ "connector_name":"my-connector", "data_collections":"table1, table2" } } ---- |Paused a|[source, json] ---- { "id":"068d07a5-d16b-4c4a-b95f-8ad061a69d51", "aggregate_type":"Incremental Snapshot", "type":"PAUSED", "additional_data":{ "connector_name":"my-connector", "data_collections":"table1, table2" } } ---- |Resumed a|[source, json] ---- { "id":"a9468204-769d-430f-96d2-b0933d4839f3", "aggregate_type":"Incremental Snapshot", "type":"RESUMED", "additional_data":{ "connector_name":"my-connector", "data_collections":"table1, table2" } } ---- |Stopped a|[source, json] ---- { "id":"83fb3d6c-190b-4e40-96eb-f8f427bf482c", "aggregate_type":"Incremental Snapshot", "type":"ABORTED", "additional_data":{ "connector_name":"my-connector" } } ---- |Processing chunk a|[source, json] ---- { "id":"d02047d6-377f-4a21-a4e9-cb6e817cf744", "aggregate_type":"Incremental Snapshot", "type":"IN_PROGRESS", "additional_data":{ "connector_name":"my-connector", "data_collections":"table1, table2", "current_collection_in_progress":"table1", "maximum_key":"100", "last_processed_key":"50" } } ---- |Snapshot completed for a table a|[source, json] ---- { "id":"6d82a3ec-ba86-4b36-9168-7423b0dd5c1d", "aggregate_type":"Incremental Snapshot", "type":"TABLE_SCAN_COMPLETED", "additional_data":{ "connector_name":"my-connector", "data_collection":"table1", "total_rows_scanned":"100" } } ---- |Completed a|[source, json] ---- { "id":"6d82a3ec-ba86-4b36-9168-7423b0dd5c1d", "aggregate_type":"Incremental Snapshot", "type":"COMPLETED", "additional_data":{ "connector_name":"my-connector" } } ---- |=== // Type: procedure [id="enabling-debezium-notifications"] === Enabling {prodname} notifications To enable Debezium to emit notifications, specify a list of notification channels by setting the `notification.enabled.channels` configuration property. By default, the following notification channels are available: * `sink` * `log` To use the `sink` notification channel, you must also set the `notification.sink.topic.name` configuration property to the name of the topic where you want {prodname} to send notifications. // Type: concept [id="debezium-notification-custom-channel"] == Custom notification channels Notification mechanism has been built to be extensible. You can implement more channels where receive notification in an easy way. You need to set up a java project and add {prodname} Core dependency, implement your notification channel and deploy it. Then you just need to enable your custom channel. // Type: procedure [id="debezium-configuring-custom-notification-channels"] === Configuring custom notification channels Custom notification channels are Java classes that implement the `io.debezium.pipeline.notification.channels.NotificationChannel` service provider interface (SPI). For example: [source,java,indent=0] ---- public interface NotificationChannel { String name(); // <1> void init(CommonConnectorConfig config); // <2> void send(Notification notification); // <3> void close(); // <4> } ---- <1> The name of the channel. To enable {prodname} to use the channel, specify this name in the connector's `notification.enabled.channels` property. <2> Initializes specific configuration, variables, or connections that the channel requires. <3> Sends the notification on the channel. {prodname} calls this method to report its status. <4> Closes all allocated resources. {prodname} calls this method when the connector is stopped. // Type: concept [id="debezium-core-module-dependency"] === {prodname} core module dependencies A custom notification channel Java project has compile dependencies on the {prodname} core module. You must include these compile dependencies in your project's `pom.xml` file, as shown in the following example: [source,xml] ---- io.debezium debezium-core ${version.debezium} // <1> ---- <1> `${version.debezium}` represents the version of the {prodname} connector. Declare your implementation in the `META-INF/services/io.debezium.pipeline.notification.channels.NotificationChannel` file. // Type: procedure [id="deploying-a-debezium-custom-notification-channel"] === Deploying a custom notification channel .Prerequisites * You have a custom notification channel Java program. .Procedure * To use a notification channel with a {prodname} connector, export the Java project to a JAR file, and copy the file to the directory that contains the JAR file for each {prodname} connector that you want to use it with. + + For example, in a typical deployment, the {prodname} connector files are stored in subdirectories of a Kafka Connect directory (`/kafka/connect`), with each connector JAR in its own subdirectory (`/kafka/connect/debezium-connector-db2`, `/kafka/connect/debezium-connector-mysql`, and so forth). To use a signaling channel with a connector, add the converter JAR file to the connector's subdirectory. NOTE: To use a custom notification channel with multiple connectors, you must place a copy of the notification channel JAR file in each connector subdirectory. // Type: procedure [id="configuring-a-connectors-to-use-a-custom-notification-channel"] === Configuring a connector to use a custom notification channel Add the name of the custom notification channel to the `notification.enabled.channels` configuration property.