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TACO (TCP Availability Connection Observer)

This is a simple Go application with zero external dependencies that checks if a specified TCP target is available. It continuously attempts to connect to the specified target at regular intervals until the target becomes available or the program is terminated.

Environment Variables

TACO accepts the following environment variables:

  • TARGET_ADDRESS: The address of the target in the format host:port (required).
  • TARGET_NAME: The name of the target to check (optional, default: inferred from TARGET_ADDRESS)*.
  • INTERVAL: The interval between connection attempts (optional, default: 2s).
  • DIAL_TIMEOUT: The timeout for each connection attempt (optional, default: 1s).
  • LOG_ADDITIONAL_FIELDS: Log additional fields (optional, default: false).

* If TARGET_NAME is not set, the name will be inferred from the host part of the target address as follows: postgres.default.svc.cluster.local:5432 will be inferred as postgres.

Behavior Flowchart

graph TD;
    A[Start] --> B[Attempt to connect to TARGET_ADDRESS];
    B -->|Connection successful| C[Target is ready];
    B -->|Connection failed| D[Wait for retry INTERVAL];
    D --> B;
    C --> E[End];
    F[Program terminated or canceled] --> E;
Loading

Logging

With the LOG_ADDITIONAL_FIELDS environment variable set to true additional fields will be logged.

With additional fields

ts=2024-07-05T13:08:20+02:00 level=INFO msg="Waiting for PostgreSQL to become ready..." dial_timeout="1s" interval="2s" target_address="postgres.default.svc.cluster.local:5432" target_name="PostgreSQL" version="0.0.22"
ts=2024-07-05T13:08:21+02:00 level=WARN msg="PostgreSQL is not ready ✗" dial_timeout="1s" error="dial tcp: lookup postgres.default.svc.cluster.local: i/o timeout" interval="2s" target_address="postgres.default.svc.cluster.local:5432" target_name="PostgreSQL" version="0.0.22"
ts=2024-07-05T13:08:24+02:00 level=WARN msg="PostgreSQL is not ready ✗" dial_timeout="1s" error="dial tcp: lookup postgres.default.svc.cluster.local: i/o timeout" interval="2s" target_address="postgres.default.svc.cluster.local:5432" target_name="PostgreSQL" version="0.0.22"
ts=2024-07-05T13:08:27+02:00 level=WARN msg="PostgreSQL is not ready ✗" dial_timeout="1s" error="dial tcp: lookup postgres.default.svc.cluster.local: i/o timeout" interval="2s" target_address="postgres.default.svc.cluster.local:5432" target_name="PostgreSQL" version="0.0.22"
ts=2024-07-05T13:08:27+02:00 level=INFO msg="PostgreSQL is ready ✓" dial_timeout="1s" error="dial tcp: lookup postgres.default.svc.cluster.local: i/o timeout" interval="2s" target_address="postgres.default.svc.cluster.local:5432" target_name="PostgreSQL" version="0.0.22"

Without additional fields

time=2024-07-12T12:44:41.494Z level=INFO msg="Waiting for PostgreSQL to become ready..."
time=2024-07-12T12:44:41.512Z level=WARN msg="PostgreSQL is not ready ✗"
time=2024-07-12T12:44:43.532Z level=WARN msg="PostgreSQL is not ready ✗"
time=2024-07-12T12:44:45.552Z level=INFO msg="PostgreSQL is ready ✓"

Kubernetes initContainer Configuration

Configure your Kubernetes deployment to use this init container:

initContainers:
  - name: wait-for-valkey
    image: ghcr.io/containeroo/taco:latest
    env:
      - name: TARGET_NAME
        value: valkey
      - name: TARGET_ADDRESS
        value: valkey.default.svc.cluster.local:6379
      - name: INTERVAL
        value: "2s" # Specify the interval duration, e.g., 2 seconds
      - name: DIAL_TIMEOUT
        value: "2s" # Specify the dial timeout duration, e.g., 2 seconds
      - name: LOG_ADDITIONAL_FIELDS
        value: "true"
  - name: wait-for-postgres
    image: ghcr.io/containeroo/taco:latest
    env:
      - name: TARGET_NAME
        value: PostgreSQL
      - name: TARGET_ADDRESS
        value: postgres.default.svc.cluster.local:5432
      - name: INTERVAL
        value: "2s" # Specify the interval duration, e.g., 2 seconds
      - name: DIAL_TIMEOUT
        value: "2s" # Specify the dial timeout duration, e.g., 2 seconds
      - name: LOG_ADDITIONAL_FIELDS
        value: "true"