CircleCI Build Failed: Troubleshooting OOM, Permissions, and Timeouts

Understanding the 'CircleCI Build Failed' Error

When working in fast-paced DevOps environments, encountering a 'CircleCI build failed' notification is a daily reality. The phrase 'build failed' is a blanket term that encompasses a wide variety of pipeline failures. Unlike local development where you have immediate access to your shell and IDE debugger, CI/CD failures happen in ephemeral, isolated containers or virtual machines. This means troubleshooting requires a specific methodology: parsing logs, understanding exit codes, and replicating the environment.

In this comprehensive guide, we will break down the three most common reasons your CircleCI pipelines are failing: Out of Memory (OOM) errors, Permission Denied errors, and Build Timeouts. We will explore the exact error messages you will see in the CircleCI UI, the root causes behind them, and step-by-step actionable solutions to get your builds back to green.

1. Out of Memory (OOM) - Exit Code 137

The Symptom

One of the most frequent culprits for a failed build in CircleCI—especially in Node.js, Java, or Docker-heavy pipelines—is the dreaded OOM killer. You will typically see a build fail abruptly with an error similar to this:

Exited with code exit status 137

Or, if you are running a Java application, you might see:

java.lang.OutOfMemoryError: Java heap space

Exit code 137 is standard Linux shorthand for a process that was killed by the SIGKILL (signal 9) sent by the Linux kernel's OOM Killer. The kernel intervenes when the container exceeds its allocated RAM, destroying the process to protect the host system.

Step 1: Diagnose

To confirm an OOM issue, look at the step that failed. Is it a Webpack build? A Maven test suite? A Docker image build? If the step abruptly stopped without an internal application error stack trace, it's highly likely it hit the memory ceiling. CircleCI limits the memory available based on the resource_class defined in your .circleci/config.yml. By default, Docker executors use the medium resource class, which provides 2 vCPUs and 4GB of RAM.

Step 2: Fix

There are two primary ways to resolve OOM errors: allocate more memory or optimize your application's memory footprint.

Solution A: Increase the Resource Class The fastest fix is to give the container more RAM. Edit your .circleci/config.yml and update the resource_class parameter for the failing job.

jobs:
  build:
    docker:
      - image: cimg/node:18.14.0
    resource_class: large # Upgrades to 4 vCPU and 8GB RAM
    steps:
      - checkout
      - run: npm run build

Note: Increasing the resource class consumes more CircleCI credits per minute.

Solution B: Limit Node.js/Java Memory Usage If your application doesn't need more memory, but is just aggressively consuming it (like Node.js garbage collection running too late), you can constrain the runtime. For Node.js, set the max_old_space_size in your run step: NODE_OPTIONS="--max_old_space_size=3072" npm run build (Leaves ~1GB for the OS in a 4GB container).

For Java, set JVM arguments: JAVA_TOOL_OPTIONS="-Xmx3200m" mvn verify

2. Permission Denied (403) and Authentication Failures

The Symptom

Permission errors manifest in several ways depending on the resource you are trying to access. Common error messages include:

• Permission denied (publickey). fatal: Could not read from remote repository. (Git clone failure)
• 403 Forbidden (AWS S3, GCP, or NPM registry upload)
• Error response from daemon: Get https://registry-1.docker.io/v2/: unauthorized (Docker Hub pull rate limit or bad auth)

Step 1: Diagnose

Permission denied errors mean your CircleCI runner lacks the necessary credentials (SSH keys, API tokens, or IAM roles) to communicate with an external service. Determine what service is rejecting the connection. Is it GitHub? AWS? Docker Hub?

Step 2: Fix

Fixing SSH Key Issues (GitHub/Bitbucket) If your build fails during the checkout step or when pulling a private Git submodule, the runner doesn't have the right SSH key.

1. Go to your CircleCI Project Settings > SSH Keys.
2. Add a user key or a deploy key that has read access to the target repository.
3. In your config.yml, ensure the add_ssh_keys step is present before checkout if pulling submodules.

Fixing Cloud Provider Auth (AWS/GCP) If a deployment step fails with a 403, your API keys are likely missing, expired, or lack the correct IAM policies.

1. Verify your Environment Variables in Project Settings or Contexts.
2. Ensure variables like AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY are spelled correctly.
3. Best Practice: Migrate from long-lived API keys to OpenID Connect (OIDC). CircleCI provides a built-in OIDC token ($CIRCLE_OIDC_TOKEN) that you can use to assume an AWS IAM role temporarily. This eliminates the need to store static secrets in CircleCI.

3. CircleCI Timeout Issues

The Symptom

Sometimes a build doesn't fail with a specific error; it just spins until CircleCI forcibly terminates it. You will see:

Too long with no output (exceeded 10m0s): context deadline exceeded

Step 1: Diagnose

By default, CircleCI will kill any step that does not produce standard output (stdout/stderr) for 10 minutes. This is a safety mechanism to prevent stuck jobs from draining your credit balance. Identify the step. Is it a massive test suite? A script waiting for a database to boot? A prompt waiting for user input?

Step 2: Fix

Solution A: Increase no_output_timeout If the command is legitimately doing heavy lifting silently (like a complex database migration or compiling a massive C++ library), you can override the default timeout for that specific run step.

steps:
  - run:
      name: Compile heavy binary
      command: make build-all
      no_output_timeout: 30m

Solution B: Prevent Silent Hangs If the script is waiting for user input (e.g., an apt-get install prompting [Y/n]), it will hang until it times out. Always use non-interactive flags in CI:

• Replace apt-get install tree with apt-get install -y tree
• Replace npm init with npm init -y

If a background service (like a test database) is holding up the pipeline, ensure you use the background: true flag in your .circleci/config.yml for the service boot step, and use a tool like dockerize -wait to poll for its readiness before running tests.

Master Debugging Strategy: SSH into the Build

When logs aren't enough, CircleCI's best feature is 'Rerun job with SSH'.

1. Click the 'Rerun' dropdown on the failed job.
2. Select 'Rerun Job with SSH'.
3. CircleCI will provision the container, run the steps up to the failure, and hold the container open.
4. Copy the provided SSH command into your local terminal.
5. You are now inside the exact environment where the build failed. You can inspect /var/log, check environment variables with printenv, and manually execute the failing script to see real-time output.

Mastering these debugging techniques will drastically reduce your time-to-resolution for pipeline failures, keeping your deployment velocity high.