How a SNAPSHOT Caused a 2-Hour Outage (And How We Fixed It)

Everyone talks about CI/CD, but few discuss the discipline that makes pipelines bulletproof. After a painful outage, our team learned this lesson the hard way. Here’s how we turned chaos into control by mastering the art of immutable artifacts—and why SNAPSHOT vs. RELEASE versions became our non-negotiable rule.

The Incident: A "Quick Fix" That Broke Production

It started like any other firefight. A critical bug was reported, and a developer urgently built and manually deployed a SNAPSHOT artifact to a pre-production environment for testing.

"The tests passed! Let's promote it."

The problem? The SNAPSHOT artifact was mutable. Between the time it was tested and the time it was promoted, a hidden dependency changed. The result? A cascading failure that took down production for two hours.

We weren’t just battling code bugs; we were battling environmental drift **and **artifact mutability. Our process was broken.

The Solution: Embracing Immutability

We adopted a strict, two-tiered artifact strategy:

SNAPSHOT Versions: The "draft" state. Mutable, fluid, and for development and testing only.

RELEASE Versions:The "contract." Immutable, versioned, auditable, and the only thing production ever sees.

This wasn’t just a technical change; it was a cultural shift. We moved from "it works on my machine" to "what we test is what we deploy."

The Technical Enforcement: How We Made It Stick

A rule without enforcement is just a suggestion. Here’s how we automated this discipline into our pipeline:

1. Pipeline Gates in CI/CD

We added a hard check in our Jenkins pipeline to block any promotion of a SNAPSHOT to a production environment.

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                sh 'mvn clean package' // Creates app-1.0.0-SNAPSHOT.jar
            }
        }
        stage('Test') {
            steps {
                sh 'mvn test'
            }
        }
        stage('Promote to Staging') {
            steps {
                script {
                    // FAIL THE BUILD IF IT'S A SNAPSHOT
                    if (env.JOB_NAME.contains("SNAPSHOT")) {
                        error("❌ Cannot promote SNAPSHOT artifacts to staging!")
                    }
                    echo "✅ Promoting RELEASE version to staging..."
                }
            }
        }
    }
}

2. Repository Manager Policies

We configured our Nexus repository to physically reject SNAPSHOT deployments to our production-ready repository.

3. The Promotion Workflow

Our entire process became:

Build and test app-1.0.0-SNAPSHOT.jar.

Upon success, promote the artifact to an immutable app-1.0.0.jar.

Every environment, from staging to production, deploys only the exact, immutable app-1.0.0.jar binary.

The Results
🚀 Zero Deployment Surprises: No more "it worked in staging" failures.

⚡ Faster Rollbacks: Rolling back meant redeploying a known-good, immutable release.

🤝 Trust: Developers deployed with confidence, and the business trusted our process.

How You Can Implement This
Audit Your Artifacts: Are SNAPSHOTs leaking into prod?

Automate Gates: Add simple checks in your pipeline today.

Cultivate Discipline: Make immutable releases a cultural norm.

This shift is the difference between hoping for the best and knowing for a fact that your deployment is stable.

Have you faced a similar challenge? How did you solve it? Share your stories and solutions in the comments below!