Wait4X

Wait4X is a lightweight, zero-dependency tool to wait for services to be ready. Perfect for CI/CD, containers, and local development.

📑 Table of Contents

• Overview
• Features
• Installation
• Quick Start
• Usage Examples
• Advanced Features
• Go Package Usage
• CLI Reference
• Contributing
• License

Overview

Wait4X helps you wait for services (databases, APIs, message queues, etc.) to be ready before your app or script continues. It's ideal for:

• CI/CD pipelines: Ensure dependencies are up before tests run
• Containers & orchestration: Health check services before startup
• Deployments: Verify readiness before rollout
• Local development: Simplify service readiness checks

Features

📥 Installation

After installing, jump to Quick Start to try it out!

# Pull the image
docker pull wait4x/wait4x:latest

# Run the container
docker run --rm wait4x/wait4x:latest --help

brew install wait4x

apk add wait4x

yay -S wait4x-bin

nix-env -iA nixpkgs.wait4x

scoop install wait4x

curl -LO https://github.com/wait4x/wait4x/releases/latest/download/wait4x-linux-amd64.tar.gz
tar -xf wait4x-linux-amd64.tar.gz -C /tmp
sudo mv /tmp/wait4x-linux-amd64/wait4x /usr/local/bin/

curl -LO https://github.com/wait4x/wait4x/releases/latest/download/wait4x-darwin-amd64.tar.gz
tar -xf wait4x-darwin-amd64.tar.gz -C /tmp
sudo mv /tmp/wait4x-darwin-amd64/wait4x /usr/local/bin/

curl -LO https://github.com/wait4x/wait4x/releases/latest/download/wait4x-windows-amd64.tar.gz
tar -xf wait4x-windows-amd64.tar.gz
# Move to a directory in your PATH

curl -LO https://github.com/wait4x/wait4x/releases/latest/download/wait4x-linux-amd64.tar.gz.sha256sum
sha256sum --check wait4x-linux-amd64.tar.gz.sha256sum

go install wait4x.dev/v3/cmd/wait4x@latest

🚀 Quick Start

Get started in seconds! After installing, try these common checks:

Wait for a TCP Port

wait4x tcp localhost:3306

HTTP Health Check

wait4x http https://example.com/health --expect-status-code 200

Wait for Multiple Services (Parallel)

wait4x tcp 127.0.0.1:5432 127.0.0.1:6379 127.0.0.1:27017

Database Readiness

wait4x postgresql 'postgres://user:pass@localhost:5432/mydb?sslmode=disable'

For more, see Usage Examples or Detailed Usage.

Usage Examples

Here are some of the most useful Wait4X commands. Click the links for more details!

• TCP: Wait for a port to be available
  wait4x tcp localhost:8080
• HTTP: Wait for a web endpoint with status code and body check
  wait4x http https://api.example.com/health --expect-status-code 200 --expect-body-regex '"status":"UP"'
• DNS: Wait for DNS A record
  wait4x dns A example.com
• MySQL: Wait for MySQL DB
  wait4x mysql 'user:password@tcp(localhost:3306)/mydb'
• Redis: Wait for Redis and check for a key
  wait4x redis redis://localhost:6379 --expect-key "session:active"
• Run a command after check:
  wait4x tcp localhost:8080 -- ./start-app.sh
• Reverse check (wait for port to be free):
  wait4x tcp localhost:8080 --invert-check
• Parallel check:
  wait4x tcp localhost:3306 localhost:6379 localhost:27017

See Detailed Usage for advanced options and more protocols.

📖 Detailed Usage

Jump to:

• HTTP Checking
• DNS Checking
• Database Checking
• Message Queue Checking
• Shell Command

HTTP Checking

Wait for an HTTP(S) endpoint to be ready, with flexible validation options.

• Status code check:

  wait4x http https://api.example.com/health --expect-status-code 200
  

• Response body regex:

  wait4x http https://api.example.com/status --expect-body-regex '"status":\s*"healthy"'
  

• JSON path check:

  wait4x http https://api.example.com/status --expect-body-json "services.database.status"
  

  Uses GJSON Path Syntax.
• XPath check:

  wait4x http https://example.com --expect-body-xpath "//div[@id='status']"
  

• Custom request headers:

  wait4x http https://api.example.com \
    --request-header "Authorization: Bearer token123" \
    --request-header "Content-Type: application/json"
  

• Response header check:

  wait4x http https://api.example.com --expect-header "Content-Type=application/json"
  

• TLS options:

  wait4x http https://www.wait4x.dev --cert-file /path/to/certfile --key-file /path/to/keyfile
  wait4x http https://www.wait4x.dev --ca-file /path/to/cafile
  

DNS Checking

Check for various DNS record types and values.

• A record:

  wait4x dns A example.com
  wait4x dns A example.com --expected-ip 93.184.216.34
  wait4x dns A example.com --expected-ip 93.184.216.34 -n 8.8.8.8
  

• AAAA record (IPv6):

  wait4x dns AAAA example.com --expected-ip "2606:2800:220:1:248:1893:25c8:1946"
  

• CNAME record:

  wait4x dns CNAME www.example.com --expected-domain example.com
  

• MX record:

  wait4x dns MX example.com --expected-domain "mail.example.com"
  

• NS record:

  wait4x dns NS example.com --expected-nameserver "ns1.example.com"
  

• TXT record:

  wait4x dns TXT example.com --expected-value "v=spf1 include:_spf.example.com ~all"
  

Database Checking

Check readiness for popular databases.

MySQL

• TCP connection:

  wait4x mysql 'user:password@tcp(localhost:3306)/mydb'
  

• Unix socket:

  wait4x mysql 'user:password@unix(/var/run/mysqld/mysqld.sock)/mydb'
  

• Check if a table exists:

  wait4x mysql 'user:password@tcp(localhost:3306)/mydb' --expect-table my_table
  

PostgreSQL

• TCP connection:

  wait4x postgresql 'postgres://user:password@localhost:5432/mydb?sslmode=disable'
  

• Unix socket:

  wait4x postgresql 'postgres://user:password@/mydb?host=/var/run/postgresql'
  

• Check if a table exists:

  wait4x postgresql 'postgres://user:password@localhost:5432/mydb?sslmode=disable' --expect-table my_table
  

  If you need to specify a schema for the table existence check, you can use the currentSchema=myschema connection string parameter, for example:

  wait4x postgresql 'postgres://user:password@localhost:5432/mydb?sslmode=disable&currentSchema=myschema' --expect-table my_table
  

MongoDB

wait4x mongodb 'mongodb://user:password@localhost:27017/mydb?maxPoolSize=20'

Redis

• Basic connection:

  wait4x redis redis://localhost:6379
  

• With authentication and DB selection:

  wait4x redis redis://user:password@localhost:6379/0
  

• Check for key existence:

  wait4x redis redis://localhost:6379 --expect-key "session:active"
  

• Check for key with value (regex):

  wait4x redis redis://localhost:6379 --expect-key "status=^ready$"
  

InfluxDB

wait4x influxdb http://localhost:8086

Message Queue Checking

RabbitMQ

wait4x rabbitmq 'amqp://guest:guest@localhost:5672/myvhost'

Temporal

• Server check:

  wait4x temporal server localhost:7233
  

• Worker check (namespace & task queue):

  wait4x temporal worker localhost:7233 \
    --namespace my-namespace \
    --task-queue my-queue
  

• Check for specific worker identity:

  wait4x temporal worker localhost:7233 \
    --namespace my-namespace \
    --task-queue my-queue \
    --expect-worker-identity-regex "worker-.*"
  

Kafka

• Basic Kafka broker readiness check:

  wait4x kafka kafka://localhost:9092
  

• Check Kafka broker with SCRAM authentication:

  wait4x kafka kafka://user:pass@localhost:9092?authMechanism=scram-sha-256
  

• Wait for multiple Kafka brokers (cluster) to be ready:

  wait4x kafka kafka://broker1:9092 kafka://broker2:9092 kafka://broker3:9092
  

Notes:

• The connection string format is: kafka://[user:pass@]host:port[?option=value&...]
• Supported options: authMechanism (scram-sha-256, scram-sha-512)

Shell Command

Wait for a shell command to succeed or return a specific exit code.

• Check connection:

  wait4x exec 'ping wait4x.dev -c 2'
  

• Check file existence:

  wait4x exec 'ls target/debug/main' --exit-code 2
  

See Advanced Features for timeout, retry, backoff, and parallel/reverse checking options.

⚙️ Advanced Features

Jump to:

• Timeout & Retry Control
• Exponential Backoff
• Reverse Checking
• Command Execution
• Parallel Checking

Timeout & Retry Control

Control how long Wait4X waits and how often it checks.

• Set a timeout:

  wait4x tcp localhost:8080 --timeout 30s
  

  Waits up to 30 seconds before giving up.

• Set check interval:

  wait4x tcp localhost:8080 --interval 2s
  

  Checks every 2 seconds (default: 1s).

Exponential Backoff

Retry with increasing delays for more efficient waiting (useful for slow-starting services).

• Enable exponential backoff:

  wait4x http https://api.example.com \
    --backoff-policy exponential \
    --backoff-exponential-coefficient 2.0 \
    --backoff-exponential-max-interval 30s
  

  Doubles the wait time between retries, up to 30 seconds.

Reverse Checking

Wait for a service to become unavailable (e.g., port to be free, service to stop).

• Wait for a port to become free:

  wait4x tcp localhost:8080 --invert-check
  

• Wait for a service to stop:

  wait4x http https://service.local/health --expect-status-code 200 --invert-check
  

  Use for shutdown/cleanup workflows or to ensure a port is not in use.

Command Execution

Run a command after a successful check (great for CI/CD or startup scripts).

• Run a script after waiting:

  wait4x tcp localhost:3306 -- ./deploy.sh
  

• Chain multiple commands:

  wait4x redis redis://localhost:6379 -- echo "Redis is ready" && ./init-redis.sh
  

  Automate your workflow after dependencies are ready.

Parallel Checking

Wait for multiple services at once (all must be ready to continue).

• Check several services in parallel:

  wait4x tcp localhost:3306 localhost:6379 localhost:27017
  

  Use for microservices, integration tests, or complex startup dependencies.

See CLI Reference for all available flags and options.

📦 Go Package Usage

go get wait4x.dev/v3

import (
    "context"
    "time"

    "wait4x.dev/v3/checker/tcp"      // TCP checker
    "wait4x.dev/v3/checker/http"     // HTTP checker
    "wait4x.dev/v3/checker/redis"    // Redis checker
    "wait4x.dev/v3/waiter"           // Waiter functionality
)

// Create a context with timeout
ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
defer cancel()

// Create a TCP checker
tcpChecker := tcp.New("localhost:6379", tcp.WithTimeout(5*time.Second))

// Wait for the TCP port to be available
err := waiter.WaitContext(
    ctx,
    tcpChecker,
    waiter.WithTimeout(time.Minute),
    waiter.WithInterval(2*time.Second),
    waiter.WithBackoffPolicy("exponential"),
)
if err != nil {
    log.Fatalf("Failed to connect: %v", err)
}

fmt.Println("Service is ready!")

// Create HTTP headers
headers := http.Header{}
headers.Add("Authorization", "Bearer token123")
headers.Add("Content-Type", "application/json")

// Create an HTTP checker with validation
checker := http.New(
    "https://api.example.com/health",
    http.WithTimeout(5*time.Second),
    http.WithExpectStatusCode(200),
    http.WithExpectBodyJSON("status"),
    http.WithExpectBodyRegex(`"healthy":\s*true`),
    http.WithExpectHeader("Content-Type=application/json"),
    http.WithRequestHeaders(headers),
)

// Wait for the API to be ready
err := waiter.WaitContext(ctx, checker, options...)

// Create checkers for multiple services
checkers := []checker.Checker{
    redis.New("redis://localhost:6379"),
    postgresql.New("postgres://user:pass@localhost:5432/db"),
    http.New("http://localhost:8080/health"),
}

// Wait for all services in parallel
err := waiter.WaitParallelContext(
    ctx,
    checkers,
    waiter.WithTimeout(time.Minute),
    waiter.WithBackoffPolicy(waiter.BackoffPolicyExponential),
)

// Define your custom checker
type FileChecker struct {
    filePath string
    minSize  int64
}

// Implement Checker interface
func (f *FileChecker) Identity() (string, error) {
    return fmt.Sprintf("file(%s)", f.filePath), nil
}

func (f *FileChecker) Check(ctx context.Context) error {
    // Check if context is done
    select {
    case <-ctx.Done():
        return ctx.Err()
    default:
        // Continue checking
    }

    fileInfo, err := os.Stat(f.filePath)
    if err != nil {
        if os.IsNotExist(err) {
            return checker.NewExpectedError(
                "file does not exist",
                err,
                "path", f.filePath,
            )
        }
        return err
    }

    if fileInfo.Size() < f.minSize {
        return checker.NewExpectedError(
            "file is smaller than expected",
            nil,
            "path", f.filePath,
            "actual_size", fileInfo.Size(),
            "expected_min_size", f.minSize,
        )
    }

    return nil
}

For more detailed examples with complete code, see the examples/pkg directory. Each example is in its own directory with a runnable main.go file.

📝 CLI Reference

Wait4X provides a flexible CLI with many commands and options. Here is a summary of the main commands and global flags. For the most up-to-date and detailed information, use the built-in help:

wait4x --help
wait4x <command> --help

Main Commands

Each command supports its own set of flags. See examples above or run wait4x <command> --help for details.

Global Flags

Getting Help

For a full list of commands and options, run:

wait4x --help
wait4x <command> --help

🤝 Contributing

We welcome contributions of all kinds! Whether you want to fix a bug, add a feature, improve documentation, or help others, you're in the right place.

How to contribute:

1. Fork the repository
2. Create a feature branch: git checkout -b feature/your-feature-name
3. Make your changes (add tests if possible)
4. Run tests: make test
5. Commit: git commit -am 'Describe your change'
6. Push: git push origin feature/your-feature-name
7. Open a Pull Request

Found a bug or have a feature request?

• Report an issue

For more details, see CONTRIBUTING.md (if available).

💬 Community & Support

• 💡 Questions or ideas? Use GitHub Discussions
• 🐞 Bugs or feature requests? Open an issue
• ⭐ Star the repo to support the project!

📄 License

This project is licensed under the Apache License 2.0 - see the LICENSE file for details.

Copyright 2019-2025 The Wait4X Authors

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

Credits

The project logo is based on the "Waiting Man" character (Zhdun) and is used with attribution to the original creator.