How can you efficiently update a large Docker image without long delays?

For efficient updating of a large Docker image without long delays, the following approaches should be used:

• Layered caching: Docker stores images in layers. When updating, modify only those layers that have actually changed to reuse the cache of the others.
• Minimizing changes in base layers: The fewer changes in the base image, the faster the update.
• Using multi-stage builds: Allows reducing the final image size by removing unnecessary dependencies and artifacts.
• Optimizing Dockerfile: For example, combining RUN commands, proper order of instructions for maximum caching.
• Using delta updates: Deployment can utilize tools that transmit only the changed parts of the image.

Example of Dockerfile optimization:

FROM golang:1.20 AS builder
WORKDIR /app
COPY go.mod go.sum ./
RUN go mod download
COPY . .
RUN go build -o myapp

FROM alpine:latest
COPY --from=builder /app/myapp /usr/local/bin/myapp
CMD ["myapp"]

Here, dependencies are downloaded first, then the rest of the code is copied, which allows caching layers with dependencies and avoiding rebuilding them unnecessarily.