postgresworker

README

Example

This is example for create Postgres Event Listener, inspired by Hasura Event Triggers

Create delivery handler

package workerhandler

import (
	"context"
	"encoding/json"
	
	"example.service/internal/modules/examplemodule/delivery/workerhandler"

	"github.com/golangid/candi/codebase/factory/types"
	"github.com/golangid/candi/tracer"
)

// PostgresListenerHandler struct
type PostgresListenerHandler struct {
	uc        usecase.Usecase
	validator interfaces.Validator
}

// NewPostgresListenerHandler constructor
func NewPostgresListenerHandler(uc usecase.Usecase, validator interfaces.Validator) *PostgresListenerHandler {
	return &PostgresListenerHandler{
		uc:        uc,
		validator: validator,
	}
}

// MountHandlers mount handler group
func (h *PostgresListenerHandler) MountHandlers(group *types.WorkerHandlerGroup) {
	group.Add("table-names", h.handleDataChange) // listen data change on table "table-names"
}

func (h *PostgresListenerHandler) handleDataChange(ctx context.Context, message []byte) error {
	trace := tracer.StartTrace(ctx, "DeliveryPostgresListener:HandleDataChange")
	defer trace.Finish()
	ctx = trace.Context()

	fmt.Printf("data change on table 'table-names' detected: %s\n", message)
	// call usecase
	return nil
}

Register in module

package examplemodule

import (
	"example.service/internal/modules/examplemodule/delivery/workerhandler"

	"github.com/golangid/candi/codebase/factory/dependency"
	"github.com/golangid/candi/codebase/factory/types"
	"github.com/golangid/candi/codebase/interfaces"
)

type Module struct {
	// ...another delivery handler
	workerHandlers map[types.Worker]interfaces.WorkerHandler
}

func NewModules(deps dependency.Dependency) *Module {
	return &Module{
		workerHandlers: map[types.Worker]interfaces.WorkerHandler{
			// ...another worker handler
			// ...
			types.PostgresListener: workerhandler.NewPostgresListenerHandler(usecaseUOW.User(), deps.GetValidator()),
		},
	}
}

// ...another method

JSON Payload

Received on messages ([]byte data type) in handler param.

{
  "table": "<table-name>",
  "action": "<operation-name>", // INSERT, UPDATE, or DELETE
  "data": {
    "old": <old-column-values-object>,
    "new": <new-column-values-object>
  }
}

Documentation

Index

• func NewWorker(service factory.ServiceFactory, postgresDSN string) factory.AppServerFactory
• type EventPayload

Functions

func NewWorker

func NewWorker(service factory.ServiceFactory, postgresDSN string) factory.AppServerFactory

NewWorker create new postgres event listener

Types

type EventPayload

type EventPayload struct {
	Table  string `json:"table"`
	Action string `json:"action"`
}

EventPayload event model