vishnubob/wait-for-it
Wait For It
wait-for-it is a Bash-based service dependency tool and network utility designed to verify TCP port availability. It functions as a connection wait script that pauses execution until a specific host and port are reachable.
The utility polls a remote port to ensure a service is online before starting dependent processes. Once the network condition is met or a TCP socket handshake is successful, it can trigger a secondary command to initiate subsequent automation tasks.
The script includes mechanisms for linear execution blocking and timeout-driven termination to prevent infinite hangs. These capabilities support network readiness checking and the coordination of interdependent services.
Features
- TCP Probing - Repeatedly attempts to establish a TCP connection to verify if a service is online and accepting traffic.
- Shell Command Execution - Triggers secondary shell commands based on the outcome of a network connectivity probe.
- Conditional Command Executions - Wait-for-it executes a specified subcommand after a port becomes available to trigger subsequent automation tasks.
- Container Startup Coordination - Manages the startup order of containers by waiting for dependent databases or APIs to be reachable over TCP.
- Dependency-Aware Orchestration - Ensures dependent services are fully reachable before starting a main application to prevent crashes.
- Deployment Automation - Integrates into deployment workflows by pausing scripts until required network infrastructure is ready.
- Service Dependency Tools - Provides a lightweight Bash script for coordinating the startup order of interdependent services.
- Connection Wait Scripts - Pauses execution until a specific TCP host and port are reachable and available.
- Service Coordination - Coordinates service startup by pausing execution until a specific host and port accept a connection.
- Availability Polling - Polls a specific host and port until it becomes available or a timeout is reached.
- Process Execution Sequencing - Pauses the calling process sequence to ensure strict service startup ordering.
- Network Readiness Checks - Verifies that a remote host and port are open before executing dependent automation commands.
- Execution Timeouts - Limits the duration of the polling loop to prevent infinite hangs if a service fails to start.
- Availability Probes - Polls a remote port to verify a service is online before starting dependent processes.
- Socket Connectivity Verifiers - Uses low-level network calls to verify the availability of a listener via a TCP socket handshake.
- Shell Script Runtimes - Provides a standalone shell script that runs without requiring high-level runtimes or compiled binaries.
- Deployment and DevOps - Utility for waiting on service availability in Docker.
