9.4.3.5 Logs Troubleshooting Flow

Logs troubleshooting flow describes a practical, structured approach to using docker compose logs and its various options together when actually diagnosing a problem with a running Compose application, rather than simply viewing logs without any particular strategy.

Starting With a Broad, Recent View

Beginning with a recent slice of output across every service provides initial context about what's currently happening, without being overwhelmed by complete historical output.

docker compose logs --tail=50

Narrowing to the Specific Service Showing Symptoms

Once a particular service appears implicated, focusing specifically on that service's logs (with more history, if needed) provides a more detailed view.

docker compose logs --tail=200 api

Searching for Specific Error Patterns

Filtering log output for known error indicators helps quickly locate relevant entries within a larger volume of output.

docker compose logs api | grep -i error

Correlating Timing Across Services With Timestamps

When an issue seems to involve interaction between services, adding timestamps and viewing multiple services together helps establish the actual sequence of events.

docker compose logs -t api db | sort

Switching to Live Monitoring to Reproduce the Issue

Once initial investigation narrows down a likely cause, actively reproducing the issue while following logs live often confirms or refines the hypothesis.

docker compose logs -f api
curl http://localhost:8080/api/problematic-endpoint

Why a Structured Logs Troubleshooting Flow Matters

Approaching log-based troubleshooting with this kind of progressively narrowing structure — broad context first, then focused investigation, then live confirmation — makes more effective use of docker compose logs's various options than reviewing output without any particular strategy, generally leading to a quicker, more confident diagnosis.