@erento/nestjs-module-google-pubsub NPM

NestJS Google Pub/Sub module

Easy way to publish messages to Google Pub/Sub. Supports encrypting the message.

How to use it

Import
Import this module in the module you want to use it:
```
```typescript
imports: [
    PubSubModule.forRoot(
        {keyFilename: PUBSUB_CONFIG},
        X_PUBSUB_KEY,
        X_PUBSUB_ENCRYPTION_KEY,
        SERVICE_IDENTIFIER
    )
]
```    
```
- PUBSUB_CONFIG is the path to the file with the service account, e.g.: ./config/pubsub.config.json
- X_PUBSUB_KEY is a secret signature key to encrypt the message. This is necessary for write, but can be used in read operation to verify a signature.
- X_PUBSUB_ENCRYPTION_KEY is a secret encryption key. This is necessary for write and read.
- SERVICE_IDENTIFIER is a string represantation of a sender, e.g. "price-service", "user-service", etc.

Usage

Publish a messages:

await this.pubSubService.publishMessage<MyMessage>(
    'projects/project-name/topics/topic-name',
    { // this can be any object, in this case: MyMessage
        text: `some message`,
    },
    {
        myAttribute: 'any other attribute you need to pass',
    },
);

Read a messages:

private async onSubscriptionMessage (message: EncodedMessage): Promise<void> {
    try {
        await this.pubSubService.verifyMessage(message);
        const decryptedMessage: string = await this.pubSubService.decryptMessage(message);
        const parsedMessage: PubSubMessage<MyMessage> = JSON.parse(decryptedMessage);

        // process parsed message parsedMessage looks like: {meta: object, payload: MyMessage}

        message.ack();
    } catch (e) {
        message.nack();
    }
}

Pull for messages: In constructor run this.registerPubSubPull();. The implementation can look as follows:

import {EncodedMessage, PubSubMessage, PubSubService} from '@erento/nestjs-module-google-pubsub';

interface MyMessage {}

class MyClass {
    constructor(private readonly pubSubService: PubSubService) {
        this.registerPubSubPull();
    }

    private registerPubSubPull (): void {
        this.pubSubService.listenOnSubscription(
            'projects/project-name/subscriptions/pull-subscription-name',
            this.onSubscriptionMessage.bind(this),
            this.onSubscriptionError.bind(this),
        );
    }

    private async onSubscriptionMessage (message: EncodedMessage): Promise<void> {
        // see section above how to read a message
    }

    private onSubscriptionError (message: EncodedRequest): void {
        Log.error(`Unexpected error happened with a message: ${JSON.stringify(message)}`);
    }
}