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TFGCo EventsGateway

Development

Client



Client

Important Notice

The Events Gateway service works following the At Least Once semantics, that means it will not prevent duplicates. In case the Client loses its connection (because of networking instabilities) after sending the event to the Events Gateway server, the server will complete the request with success and send the data to Kafka, but won't be able to acknowledge the client. If the client has some retry logic (built in on async mode) it will retry to send the same event and will duplicate it.

If you really need distinct values guarantee, consider handling it on the downstream pipelines.

Configuration

About client.NewClient(...) arguments:

  • configPrefix: whatever comes just before client portion of your config
  • config: a viper config with at least a client key holding Events Gateway settings
  • logger: a logger.Logger instance
  • client: should be nil for most cases, except for unit testing
  • opts: extra []grpc.DialOption objects

client config format, with defaults:

client:
  async: false # if you want to use the async or sync dispatch
  channelBuffer: 500 # (async-only) size of the channel that holds events
  lingerInterval: 500ms # (async-only) how long to wait before sending messages, in the hopes of filling the batch
  batchSize: 10 # (async-only) maximum number of messages to send in a batch
  maxRetries: 3 # (async-only) how many times to retry a dispatch if it fails
  retryInterval: 1s # (async-only) first wait time before a retry, formula => 2^retryNumber * retryInterval
  numRoutines: 2 # (async-only) number of go routines that read from events channel and send batches
  kafkatopic: default-topic # default topic to send messages
  grpc:
    serverAddress: localhost:5000
    timeout: 500ms

Code example:

import (
  "context"

  "github.com/spf13/viper"
  "github.com/topfreegames/eventsgateway/v4"
  "github.com/topfreegames/eventsgateway/v4/logger"
)

func ConfigureEventsGateway() (*eventsgateway.Client, error) {
  config := viper.New() // empty Viper config
  config.Set("eventsgateway.client.async", true)
  config.Set("eventsgateway.client.kafkatopic", "my-client-default-topic")
  logger := &logger.NullLogger{} // Initialize you logger.Logger implementation here
  client, err := eventsgateway.NewClient("eventsgateway", config, logger, nil)
  if err != nil {
    return nil, err
  }
}

func main() {
  client, err := ConfigureEventsGateway()
  if err != nil {
    panic(err)
  }
  // here you pass along the context.Context you received,
  // DON'T pass just a context.Background() if you have a previous context.Context
  // Sync clients should handle errors accordingly
  err := client.Send(context.Background(), "event-name", map[string]string{"some": "value"})
  // Async clients error handling are transparent to the user 
  client.Send(context.Background(), "event-name", map[string]string{"some": "value"})
}

Development

Running locally

All dependencies required to produce and consume events locally are bundled in this project.

  1. make build-dev will build a development docker image for the client.
  2. make deps-start will start docker containers for zookeeper kafka, eventsgateway-api

These are the necessary dependencies for EventsGateway server.

  1. make run starts EventsGateway server.

  2. make producer executes a client that sends one dummy event.

  3. make spark-notebook runs a jupyter-notebook container with a mounted notebook to consume from Kafka and write ORC files to S3.

Checkout the localhost address to access the Web UI over the container logs.

  1. make hive-start starts hive stack containers necessary to create tables in hive-metastore and to query from a presto client.

Bootstraping Localstack bucket and prefixes

After make deps-start and before make gobblin you'll need to bootstrap localstack's s3 to transfer data from kafka.

aws --endpoint-url=http://localhost:4572 s3 mb s3://eventsgateway-local

aws --endpoint-url=http://localhost:4572 s3api put-bucket-acl --bucket eventsgateway-local --acl public-read-write

aws --endpoint-url=http://localhost:4572 s3api put-object --bucket eventsgateway-local --key output/sv-uploads-default-topic/daily/

Note that default-topic should be replaced by the topic you're using in your client, that's the one used by make testclient.

Creating topic table in Hive metastore

Run it inside docker exec -it hive_hive-server_1 sh -c "/opt/hive/bin/beeline -u jdbc:hive2://localhost:10000".

To get the commands necessary to create database and table, run the respective cell at the end of eventsgateway-streaming-orc notebook.

After creation, you need to run msck repair table table_name; from hive server container to be able to query recent data.

Querying with Presto

Install presto client, on mac brew install presto.

presto --catalog hive --schema default

presto:default >> show tables;

presto:default >> select * from defaulttopic;