#4: support Docker Compose #6
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Important Review skippedDraft detected. Please check the settings in the CodeRabbit UI or the You can disable this status message by setting the WalkthroughA Dockerfile was introduced to containerize a Go application, specifying the build steps and runtime configuration. The Docker Compose configuration was updated to add a new backend service for the application, set up dynamic port mappings for both backend and database services, and included development-specific watch and sync settings. Changes
Sequence Diagram(s)sequenceDiagram
participant Developer
participant Docker Compose
participant transat-backend (Container)
participant db (Container)
Developer->>Docker Compose: docker compose up
Docker Compose->>db (Container): Start db with port ${DB_PORT}:5432
Docker Compose->>transat-backend (Container): Build and start backend, expose ${PORT}:3000
transat-backend (Container)->>db (Container): Connect using DB env variables
Note over transat-backend (Container): Watches for code changes and restarts if needed
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Actionable comments posted: 3
🧹 Nitpick comments (3)
Dockerfile (1)
9-11: Enable static linking and strip binariesTo ensure portability and reduce the binary size, set
CGO_ENABLED=0, target Linux, and strip debug symbols:-RUN go build -o transat-backend main.go +RUN CGO_ENABLED=0 GOOS=linux go build -ldflags="-s -w" -o transat-backend main.gocompose.yml (2)
11-11: Update port-mapping comment for dynamic host portThe inline comment still mentions a fixed host port of 5432, but you’re mapping to
${DB_PORT}. Update the comment to accurately reflect the dynamic mapping:- - "${DB_PORT}:5432" # Mappe le port 5432 du conteneur au port 5432 de l'hôte + - "${DB_PORT}:5432" # Mappe le port 5432 du conteneur au port ${DB_PORT} de l'hôte
1-1: Consider specifying the Compose file versionExplicitly declaring a
version: "3.x"at the top improves clarity and ensures compatibility with Compose features and plugins.
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📒 Files selected for processing (2)
Dockerfile(1 hunks)compose.yml(1 hunks)
🔇 Additional comments (1)
compose.yml (1)
30-36: Verify Compose compatibility with thedevelopextensionThe
developkey is not part of the standard Docker Compose specification and may require plugins or experimental flags (e.g.,docker compose dev, custom tooling). Confirm that all developers and CI/CD pipelines support this extension to enable live-sync and restart behavior.
| FROM golang:1.23.4-alpine AS builder | ||
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| WORKDIR /app | ||
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| COPY go.mod go.sum ./ | ||
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| RUN go mod download && go mod verify | ||
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| COPY . . | ||
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| RUN go build -o transat-backend main.go | ||
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| EXPOSE 3000 | ||
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| ENV PORT=3000 | ||
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| ENTRYPOINT [ "./transat-backend" ] No newline at end of file |
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🛠️ Refactor suggestion
Reduce image size via multi-stage build
Right now, the final image still contains the Go toolchain and build artifacts. Introduce a second runtime stage that copies only the compiled binary into a minimal base image (e.g., Alpine or scratch). This will dramatically shrink image size and attack surface.
Add this after line 11 in your Dockerfile:
# Stage 2: production image
FROM alpine:3.18 AS runtime
WORKDIR /app
COPY --from=builder /app/transat-backend ./
EXPOSE 3000
ENV PORT=3000
ENTRYPOINT ["./transat-backend"]🤖 Prompt for AI Agents
In Dockerfile lines 1 to 17, the current image includes the full Go toolchain
and build artifacts, making it unnecessarily large. To fix this, implement a
multi-stage build by keeping the existing builder stage as is, then add a second
stage starting after line 11 using a minimal base image like alpine:3.18. In
this runtime stage, set the working directory, copy only the compiled binary
from the builder stage, expose port 3000, set the PORT environment variable, and
define the entrypoint to run the binary. This will significantly reduce the
final image size and improve security.
| build: | ||
| context: . | ||
| dockerfile: Dockerfile | ||
| command: go run main.go |
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🛠️ Refactor suggestion
Leverage the compiled binary instead of go run
Overriding the Dockerfile’s ENTRYPOINT with go run main.go requires a Go toolchain at runtime and bypasses the built artifact. Prefer using the compiled binary:
- command: go run main.go
+ command: ["./transat-backend"]🤖 Prompt for AI Agents
In compose.yml at line 19, replace the command 'go run main.go' with the
execution of the compiled binary produced by the Dockerfile build process. This
avoids requiring the Go toolchain at runtime and ensures the container runs the
built artifact as intended. Adjust the command to invoke the binary directly,
typically by specifying its path relative to the container's working directory.
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I use go run main.go because I want the code to be compiled again at each code modification, with the watch. Is it correct?
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@luclu7 You are absolutely correct! For your development setup with Docker Compose watch, using go run main.go is the right approach.
Here's why your setup works perfectly for development:
- Hot reload with recompilation: When you modify code, the
sync+restartaction syncs the files to/appand restarts the container - Fresh compilation: On restart,
go run main.gocompiles the updated source code and runs it immediately - Go toolchain available: Since you're using
golang:1.23.4-alpineas your base image, the Go compiler is available at runtime
Your current setup gives you the hot reload development experience you want. The compiled binary approach I initially suggested would be more appropriate for production deployments where:
- You want faster startup times
- You don't need the Go toolchain at runtime
- Code changes aren't expected
For production, you could consider a multi-stage Dockerfile that builds the binary and copies it to a minimal runtime image, but for development, your approach is spot on!
compose.yml
Outdated
| - db | ||
| environment: | ||
| - DB_HOST=db | ||
| - DB_PORT=${DB_PORT} |
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🛠️ Refactor suggestion
Connect to the database via the container port
Within the Docker network, the DB service listens on container port 5432; host port mappings don’t apply inter-container. Passing ${DB_PORT} (host-mapped port) may misconfigure connections. Set the backend’s DB_PORT env var to 5432:
- - DB_PORT=${DB_PORT}
+ - DB_PORT=5432📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| - DB_PORT=${DB_PORT} | |
| - DB_PORT=5432 |
🤖 Prompt for AI Agents
In compose.yml at line 26, the DB_PORT environment variable is set to
${DB_PORT}, which uses the host-mapped port. This can cause connection issues
within the Docker network because containers communicate via container ports,
not host ports. Change the value of DB_PORT to the fixed container port 5432 to
ensure proper inter-container connectivity.
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