Dockerfile手动运行正常但docker-compose运行异常的问题排查

Let me break down what's likely happening here and how to fix it:

The Core Problem #

When you use docker build manually, you're either forcing a fresh build or ensuring recent code changes are picked up, but Docker Compose's build option often reuses cached layers by default. This can create discrepancies between the image you run manually and the one Compose creates—even if your Dockerfile and compose config look correct.

Common Causes & Fixes #

1. Cached Build Layers Are Outdated

This is the most likely culprit. Compose might be using an old cached layer where your application code or dependencies weren't updated properly.

Fix:
Force Compose to rebuild all layers from scratch without using cache:

docker-compose build --no-cache
docker-compose up

This ensures every step (like COPY . . and pip install) runs with your latest code and requirements.

2. Dockerignore Is Blocking Critical Files

Check if you have a .dockerignore file in your project root that's accidentally excluding files your app needs—like the proxy-scraper-checker directory or requirements.txt. When you build manually, you might not have noticed this, but Compose respects .dockerignore just like docker build.

Fix:
Open your .dockerignore and remove any entries that block:

• The proxy-scraper-checker directory
• requirements.txt
• Any other code files your app depends on

3. Verify Build Process Details

To see exactly what's happening during the Compose build, run the build with verbose progress output:

docker-compose build --progress=plain

Compare this output to the logs from your manual docker build command. Look for differences in:

• The COPY . . step (does it copy all your files correctly?)
• The pip install step (are all dependencies being installed?)

4. Check If The Container Is Crashing

It's possible the container starts, logs the first line, then crashes immediately. When you run manually with -it, you might see error messages that don't show up in Compose's default logs.

Fix:
Run the Compose service interactively to see real-time errors:

docker-compose run --rm proxy-app

This will let you see any crash messages or exceptions that are happening after the initial "Starting scheduler..." log.

Why Pre-Built Image Works #

When you use image: my_app in Compose, you're using the exact image you built manually—one that has your latest code, dependencies, and no stale cache. The issue only arises when Compose builds the image itself and reuses outdated layers that don't match your current project state.

内容的提问来源于stack exchange，提问作者Danny