Wait4X

Wait4X allows you to wait for a port or a service to enter the requested state, with a customizable timeout and interval time.

Table of Contents

• Features
• Installation
  • with Docker
  • From binary
    • Verify SHA256 Checksum
  • From package
    • Alpine Linux
    • Arch Linux (AUR)
• Examples
  • TCP
  • HTTP
  • Redis
  • MySQL
  • PostgreSQL
  • InfluxDB
  • MongoDB
  • RabbitMQ
  • Temporal

Features

• Supports various protocols:
  • TCP
  • HTTP
• Supports various services:
  • Redis
  • MySQL
  • PostgreSQL
  • InfluxDB
  • MongoDB
  • RabbitMQ
  • Temporal
• Reverse Checking: Invert the sense of checking to find a free port or non-ready services
• Parallel Checking: You can define multiple inputs to be checked
• Exponential Backoff Checking: Retry using an exponential backoff approach to improve efficiency and reduce errors.
• CI/CD Friendly: Well-suited to be part of a CI/CD pipeline step
• Cross Platform: One single pre-built binary for Linux, Mac OSX, and Windows
• Importable: Beside the CLI tool, Wait4X can be imported as a pkg in your Go app
• Command execution: Execute your desired command after a successful wait

Installation

There are many ways to install Wait4X

with Docker

Wait4X provides automatically updated Docker images within Docker Hub. It is possible to always use the latest stable tag.

Pull the image from the docker index.

docker pull atkrad/wait4x:latest

then you can launch the wait4x container.

docker run --rm --name='wait4x' \
    atkrad/wait4x:latest --help

From binary

Choose the file matching the destination platform from the release page, copy the URL and replace the URL within the commands below:

Linux

curl -#LO https://github.com/atkrad/wait4x/releases/latest/download/wait4x-linux-amd64.tar.gz
tar --one-top-level -xvf wait4x-linux-amd64.tar.gz
cp ./wait4x-linux-amd64/wait4x /usr/local/bin/wait4x

Mac OSX

curl -#LO https://github.com/atkrad/wait4x/releases/latest/download/wait4x-darwin-amd64.tar.gz
tar --one-top-level -xvf wait4x-darwin-amd64.tar.gz
cp ./wait4x-darwin-amd64/wait4x /usr/local/bin/wait4x

Windows

curl -#LO https://github.com/atkrad/wait4x/releases/latest/download/wait4x-windows-amd64.tar.gz
tar --one-top-level -xvf wait4x-windows-amd64.tar.gz

Verify SHA256 Checksum

Wait4X generates checksum for all binaries with sha256sum to prevent against unwanted modification of binaries. To validate the archive files, download the checksum file which ends in .sha256sum for the archive file that you downloaded and use the sha256sum command line tool.

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

From package

You can find the Wait4X package in some Linux distributions.

On Alpine Linux

You can install the wait4x package from the official sources:

apk add wait4x

On Arch Linux (AUR)

You can install the wait4x package from the Arch User Repository:

yay -S wait4x

Examples

TCP

# If you want checking just tcp connection
wait4x tcp 127.0.0.1:9090

HTTP

# If you want checking just http connection
wait4x http https://ifconfig.co

# If you want checking http connection and expect specify http status code
wait4x http https://ifconfig.co --expect-status-code 200

# If you want checking http connection, status code and match the response body.
# Note: You can write any regex that compatible with Golang syntax (https://pkg.go.dev/regexp/syntax#hdr-Syntax)
wait4x http https://ifconfig.co/json --expect-status-code 200 --expect-body='"country":\s"Netherlands"'

# If you want to check a http response header
# NOTE: the value in the expected header is regex.
# Sample response header: Authorization Token 1234ABCD
# You can match it by these ways:

# Full key value:
wait4x http https://ifconfig.co --expect-header "Authorization=Token 1234ABCD"

# Value starts with:
wait4x http https://ifconfig.co --expect-header "Authorization=Token"

# Regex value:
wait4x http https://ifconfig.co --expect-header "Authorization=Token\s.+"

# Body JSON value:
# Note: the value in the expected JSON will be processed by gjson.
# Note: the complete response MUST be in JSON format to be processed. If one part of the response is JSON
# and the rest is something else like HTML, please use --expect-body instead.
# To know more about JSON syntax https://github.com/tidwall/gjson/blob/master/SYNTAX.md
wait4x http https://ifconfig.co/json --expect-body-json "user_agent.product"

# Body XPath
wait4x http https://www.kernel.org/ --expect-body-xpath "//*[@id="tux-gear"]"

# Request headers:
wait4x http https://ifconfig.co --request-header "Content-Type: application/json" --request-header "Authorization: Token 123"

# Enable exponential backoff retry
wait4x http https://ifconfig.co --expect-status-code 200 --backoff-policy exponential  --backoff-exponential-max-interval 120s --timeout 120s

Redis

# Checking Redis connection
wait4x redis redis://127.0.0.1:6379

# Specify username, password and db
wait4x redis redis://user:password@localhost:6379/1

# Checking Redis connection over unix socket
wait4x redis unix://user:password@/path/to/redis.sock?db=1

# Checking a key existence
wait4x redis redis://127.0.0.1:6379 --expect-key FOO

# Checking a key existence and matching the value
# Note: You can write any regex that compatible with Golang syntax (https://pkg.go.dev/regexp/syntax#hdr-Syntax)
wait4x redis redis://127.0.0.1:6379 --expect-key "FOO=^b[A-Z]r$"

MySQL

# Checking MySQL TCP connection
wait4x mysql user:password@tcp(localhost:5555)/dbname

# Checking MySQL UNIX Socket connection
wait4x mysql username:password@unix(/tmp/mysql.sock)/myDatabase

Syntax for the database connection string: https://github.com/go-sql-driver/mysql#dsn-data-source-name

PostgreSQL

# Checking PostgreSQL TCP connection
wait4x postgresql 'postgres://bob:secret@1.2.3.4:5432/mydb?sslmode=disable'

# Checking PostgreSQL Unix socket connection
wait4x postgresql 'postgres://bob:secret@/mydb?host=/var/run/postgresql'

Syntax for the database URL: https://pkg.go.dev/github.com/lib/pq

InfluxDB

# Checking InfluxDB connection
wait4x influxdb http://localhost:8086

MongoDB

# Checking MongoDB connection
wait4x mongodb 'mongodb://127.0.0.1:27017'

# Checking MongoDB connection with credentials and options
wait4x mongodb 'mongodb://user:pass@127.0.0.1:27017/?maxPoolSize=20&w=majority'

RabbitMQ

# Checking RabbitMQ connection
wait4x rabbitmq 'amqp://127.0.0.1:5672'

# Checking RabbitMQ connection with credentials and vhost
wait4x rabbitmq 'amqp://guest:guest@127.0.0.1:5672/vhost'

Temporal

# Checking just Temporal server health check
wait4x temporal server 127.0.0.1:7233

# Checking insecure Temporal server (no TLS)
wait4x temporal server 127.0.0.1:7233 --insecure-transport

# Checking a task queue that has registered workers (pollers) or not
wait4x temporal worker 127.0.0.1:7233 --namespace __YOUR_NAMESPACE__ --task-queue __YOUR_TASK_QUEUE__

# Checking the specific a Temporal worker (pollers)
wait4x temporal worker 127.0.0.1:7233 --namespace __YOUR_NAMESPACE__ --task-queue __YOUR_TASK_QUEUE__ --expect-worker-identity-regex ".*@__HOSTNAME__@.*"

Command Execution

We need to wait for something in order to execute something else. This feature is also supported by using -- after a feature parameter.

Let's have some scenarios:

• As soon as the MySQL server becomes ready, run a Django migration:

wait4x mysql username:password@unix(/tmp/mysql.sock)/myDatabase -- django migrate

• As soon as the new version of the website becomes ready, send an email to the support team:

wait4x http https://www.kernel.org/ --expect-body-xpath "//*[@id="website-logo"]" -- mail -s "The new version of the website has just been released" support@company < /dev/null

• Chain type: when PostgreSQL becomes ready, then wait for RabbitMQ, when it becomes ready, then run the integration tests:

wait4x postgresql 'postgres://bob:secret@/mydb?host=/var/run/postgresql' -t 1m -- wait4x rabbitmq 'amqp://guest:guest@127.0.0.1:5672/vhost' -t 30s -- ./integration-tests.sh

• Using an environment variable in the command:

EMAIL="support@company" wait4x http https://www.kernel.org/ --expect-body-xpath "//*[@id="website-logo"]" -- mail -s "New version of the website has just released" $EMAIL < /dev/null

# Or

export EMAIL="support@company"
wait4x http https://www.kernel.org/ --expect-body-xpath "//*[@id="website-logo"]" -- mail -s "New version of the website has just released" $EMAIL < /dev/null