@ovotech/kafka-pg-sink
v1.1.3
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Store kafka-node events into a postgres database
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PG Stream
Store kafka-node events into a postgres database.
Using
yarn add @ovotech/kafka-pg-sink
Each topic from the consumer stream gets its own "resolver" function that converts the message to an array of values, directly inserted as columns in the database.
INSERT INTO tableName VALUES (column1Value, column2Value ...) ON CONFLICT DO NOTHING
import { PGSinkStream, Message } from '@ovotech/kafka-pg-sink';
import { ConsumerGroupStream } from 'kafka-node';
import { Client } from 'pg';
const consumerStream = new ConsumerGroupStream(
{ kafkaHost: 'localhost:29092', groupId: 'my-group', encoding: 'buffer' },
['migration-completed'],
);
const pg = new Client('postgresql://postgres:[email protected]:5432/postgres');
const pgSink = new PGSinkStream({
pg,
topics: {
'migration-completed': {
table: 'migration_completed',
resolver: (message: Message) => {
const data = getDataSomehow(message.value);
return [data.column1, data.column2, data];
},
},
},
});
consumerStream.pipe(pgSink);
Message
is the same as the type from kafka-node
, but is more lenient on the "value field". This allows you to pre-process the message before sending it off to pg-sink, by deserializing an using avro for example.
export interface Message {
topic: string;
value: any;
offset?: number;
partition?: number;
highWaterOffset?: number;
key?: string;
}
Usage with a deserializer
You can transform kafka events with a transform stream before they arrive to the sink. For example with @ovotech/avro-stream
.
import { AvroDeserializer, AvroMessage } from '@ovotech/avro-stream';
import { PGSinkStream } from '@ovotech/kafka-pg-sink';
import { ConsumerGroupStream } from 'kafka-node';
const consumerStream = new ConsumerGroupStream(
{ kafkaHost: 'localhost:29092', groupId: 'my-group', encoding: 'buffer' },
['migration-completed'],
);
const deserializer = new AvroDeserializer('http://localhost:8080');
const pg = new Client('postgresql://postgres:[email protected]:5432/postgres');
const pgSink = new PGSinkStream({
pg,
topics: {
'migration-completed': {
table: 'migration_completed',
resolver: (message: AvroMessage) => [message.value.accountId],
},
},
});
consumerStream.pipe(deserializer).pipe(pgSink);
Errors
PGSinkStream can emit an PGSinkError
and PGSinkMultipleError
depending on whether it was processing batched or normal requests.
PGSinkError
| Property | Description | | ------------- | ----------------------------------------------------------------------------- | | message | Original error message | | chunk | The event sent from the previous stream to be saved to the database (Message) | | encoding | The buffer encoding | | originalError | The original error object that was triggered |
PGSinkMultipleError
| Property | Description |
| ------------- | ---------------------------------------------------------- |
| message | Original error message |
| chunks | An array of { chunk: Message, encoding: string }
objects |
| originalError | The original error object that was triggered |
Example error handling:
import { PGSinkStream, PGSinkError, PGSinkMultipleError } from '@ovotech/kafka-pg-sink';
const pgSink = new PGSinkStream();
pgSink.on('error', (error: PGSinkError | PGSinkMultipleError) => {
if (error instanceof PGSinkError) {
console.log(error.chunk);
}
});
Gotchas
A thing to be aware of is that node streams unpipe in an event of an error, which means that you'll need to provide your own error handling and repipe the streams if you want it to be resilient to errors.
Running the tests
The tests require a running postgres database. This is setup easily with a docker-compose from root project folder:
docker-compose up
Then you can run the tests with:
yarn test
Coding style (linting, etc) tests
Style is maintained with prettier and tslint
yarn lint
Deployment
Deployment is preferment by lerna automatically on merge / push to master, but you'll need to bump the package version numbers yourself. Only updated packages with newer versions will be pushed to the npm registry.
Contributing
Have a bug? File an issue with a simple example that reproduces this so we can take a look & confirm.
Want to make a change? Submit a PR, explain why it's useful, and make sure you've updated the docs (this file) and the tests (see test folder).
License
This project is licensed under Apache 2 - see the LICENSE file for details