cdc

README

go-pq-cdc

go-pq-cdc is designed to provide efficient and lightweight Change Data Capture (CDC) for PostgreSQL databases. The architecture leverages PostgreSQL's built-in logical replication capabilities to capture changes in the database and stream these changes to downstream systems, such as Kafka, Elasticsearch etc. The entire system is written in Golang, ensuring low resource consumption and high performance.

Debezium vs go-pq-cdc benchmark

Contents

• Why?
• Usage
• Examples
• Availability
• Configuration
• API
• Exposed Metrics
• Compatibility
• Breaking Changes

Why?

CDC systems are crucial for real-time data synchronization, analytics, and event-driven architectures. Our main goal is to build a cdc base library for faster and stateful systems.

• Postgresql to Elasticsearch Connector

Usage

go get github.com/Trendyol/go-pq-cdc

package main

import (
	"context"
	cdc "github.com/Trendyol/go-pq-cdc"
	"github.com/Trendyol/go-pq-cdc/config"
	"github.com/Trendyol/go-pq-cdc/pq/message/format"
	"github.com/Trendyol/go-pq-cdc/pq/publication"
	"github.com/Trendyol/go-pq-cdc/pq/replication"
	"github.com/Trendyol/go-pq-cdc/pq/slot"
	"log/slog"
	"os"
)

func main() {
	ctx := context.Background()
	cfg := config.Config{
		Host:      "127.0.0.1",
		Username:  "cdc_user",
		Password:  "cdc_pass",
		Database:  "cdc_db",
		DebugMode: false,
		Publication: publication.Config{
			CreateIfNotExists: true,
			Name: "cdc_publication",
			Operations: publication.Operations{
				publication.OperationInsert,
				publication.OperationDelete,
				publication.OperationTruncate,
				publication.OperationUpdate,
			},
			Tables: publication.Tables{publication.Table{
				Name:            "users",
				ReplicaIdentity: publication.ReplicaIdentityFull,
			}},
		},
		Slot: slot.Config{
			Name:                        "cdc_slot",
			CreateIfNotExists:           true,
			SlotActivityCheckerInterval: 3000,
		},
		Metric: config.MetricConfig{
			Port: 8081,
		},
		Logger: config.LoggerConfig{
			LogLevel: slog.LevelInfo,
		},
	}

	connector, err := cdc.NewConnector(ctx, cfg, Handler)
	if err != nil {
		slog.Error("new connector", "error", err)
		os.Exit(1)
	}

	defer connector.Close()
	connector.Start(ctx)
}

func Handler(ctx *replication.ListenerContext) {
	switch msg := ctx.Message.(type) {
	case *format.Insert:
		slog.Info("insert message received", "new", msg.Decoded)
	case *format.Delete:
		slog.Info("delete message received", "old", msg.OldDecoded)
	case *format.Update:
		slog.Info("update message received", "new", msg.NewDecoded, "old", msg.OldDecoded)
	}

	if err := ctx.Ack(); err != nil {
		slog.Error("ack", "error", err)
	}
}

Examples

• Simple
• Simple File Config
• PostgreSQL to Elasticsearch
• PostgreSQL to Kafka
• PostgreSQL to PostgreSQL

Availability

The go-pq-cdc operates in passive/active modes for PostgreSQL change data capture (CDC). Here's how it ensures availability:

• Active Mode: When the PostgreSQL replication slot (slot.name) is active, go-pq-cdc continuously monitors changes and streams them to downstream systems as configured.
• Passive Mode: If the PostgreSQL replication slot becomes inactive (detected via slot.slotActivityCheckerInterval), go-pq-cdc automatically captures the slot again and resumes data capturing. Other deployments also monitor slot activity, and when detected as inactive, they initiate data capturing.

This setup ensures continuous data synchronization and minimal downtime in capturing database changes.

Configuration

Variable	Type	Required	Default	Description	Options
host	string	yes	-	PostgreSQL host	Should be a valid hostname or IP address. Example: localhost.
username	string	yes	-	PostgreSQL username	Should have sufficient privileges to perform required database operations.
password	string	yes	-	PostgreSQL password	Keep secure and avoid hardcoding in the source code.
database	string	yes	-	PostgreSQL database	The database must exist and be accessible by the specified user.
debugMode	bool	no	false	For debugging purposes	Enables pprof for trace.
metric.port	int	no	8080	Set API port	Choose a port that is not in use by other applications.
logger.logLevel	string	no	info	Set logging level	[DEBUG, WARN, INFO, ERROR]
logger.logger	Logger	no	slog	Set logger	Can be customized with other logging frameworks if slog is not used.
publication.createIfNotExists	bool	no	-	Create publication if not exists. Otherwise, return publication is not exists error.
publication.name	string	yes	-	Set PostgreSQL publication name	Should be unique within the database.
publication.operations	[]string	yes	-	Set PostgreSQL publication operations. List of operations to track; all or a subset can be specified.	INSERT: Track insert operations. UPDATE: Track update operations. DELETE: Track delete operations.
publication.tables	[]Table	yes	-	Set tables which are tracked by data change capture	Define multiple tables as needed.
publication.tables[i].name	string	yes	-	Set the data change captured table name	Must be a valid table name in the specified database.
publication.tables[i].replicaIdentity	string	yes	-	Set the data change captured table replica identity [FULL, DEFAULT]	FULL: Captures all columns when a row is updated or deleted. DEFAULT: Captures only the primary key when a row is updated or deleted.
slot.createIfNotExists	bool	no	-	Create replication slot if not exists. Otherwise, return replication slot is not exists error.
slot.name	string	yes	-	Set the logical replication slot name	Should be unique and descriptive.
slot.slotActivityCheckerInterval	int	no	1000	Set the slot activity check interval time in milliseconds	Specify as an integer value in milliseconds (e.g., 1000 for 1 second).

API

Endpoint	Description
GET /status	Returns a 200 OK status if the client is able to ping the PostgreSQL server successfully.
GET /metrics	Prometheus metric endpoint.
GET /debug/pprof/*	(Only for debugMode=true) pprof

Exposed Metrics

The client collects relevant metrics related to PostgreSQL change data capture (CDC) and makes them available at the /metrics endpoint.

Metric Name	Description	Labels	Value Type
go_pq_cdc_update_total	The total number of UPDATE operations captured on specific tables.	slot_name	Counter
go_pq_cdc_delete_total	The total number of DELETE operations captured on specific tables.	slot_name	Counter
go_pq_cdc_insert_total	The total number of INSERT operations captured on specific tables.	slot_name	Counter
go_pq_cdc_cdc_latency_current	The current latency in capturing data changes from PostgreSQL.	slot_name	Gauge
go_pq_cdc_process_latency_current	The current latency in processing the captured data changes.	slot_name	Gauge
go_pq_cdc_replication_slot_slot_confirmed_flush_lsn	The last confirmed flush Log Sequence Number (LSN) in the PostgreSQL replication slot.	slot_name	Gauge
go_pq_cdc_replication_slot_slot_current_lsn	The current Log Sequence Number (LSN) being processed in the PostgreSQL replication slot.	slot_name	Gauge
go_pq_cdc_replication_slot_slot_is_active	Indicates whether the PostgreSQL replication slot is currently active (1 for active, 0 for inactive).	slot_name	Gauge
go_pq_cdc_replication_slot_slot_lag	The replication lag measured by the difference between the current LSN and the confirmed flush LSN.	slot_name	Gauge
go_pq_cdc_replication_slot_slot_retained_wal_size	The size of Write-Ahead Logging (WAL) files retained for the replication slot in bytes.	slot_name	Gauge
runtime metrics	Prometheus Collector	N/A	N/A

Grafana Dashboard

Import the grafana dashboard json file.

Compatibility

go-pq-cdc Version	Minimum PostgreSQL Server Version
0.0.2 or higher	14

Breaking Changes

Date taking effect	Version	Change	How to check
-	-	-	-

Documentation

Index

• type Connector
  • func NewConnector(ctx context.Context, cfg config.Config, listenerFunc replication.ListenerFunc) (Connector, error)
  • func NewConnectorWithConfigFile(ctx context.Context, configFilePath string, ...) (Connector, error)

Types

type Connector

type Connector interface {
	Start(ctx context.Context)
	WaitUntilReady(ctx context.Context) error
	Close()
	GetConfig() *config.Config
	SetMetricCollectors(collectors ...prometheus.Collector)
}

func NewConnector

func NewConnector(ctx context.Context, cfg config.Config, listenerFunc replication.ListenerFunc) (Connector, error)

func NewConnectorWithConfigFile

func NewConnectorWithConfigFile(ctx context.Context, configFilePath string, listenerFunc replication.ListenerFunc) (Connector, error)