pnpm fetch
Fetch packages from a lockfile into virtual store, package manifest is ignored.
Usage scenario
This command is specifically designed to improve building a docker image.
You may have read the official guide to writing a Dockerfile for a Node.js app, if you haven't read it yet, you may want to read it first.
From that guide, we learn to write an optimized Dockerfile for projects using pnpm, which looks like
FROM node:20
WORKDIR /path/to/somewhere
RUN corepack enable pnpm && corepack install -g pnpm@latest-9
# Files required by pnpm install
COPY .npmrc package.json pnpm-lock.yaml .pnpmfile.cjs ./
# If you patched any package, include patches before install too
COPY patches patches
RUN pnpm install --frozen-lockfile --prod
# Bundle app source
COPY . .
EXPOSE 8080
CMD [ "node", "server.js" ]
As long as there are no changes to .npmrc, package.json, pnpm-lock.yaml,
.pnpmfile.cjs, docker build cache is still valid up to the layer of
RUN pnpm install --frozen-lockfile --prod, which cost most of the time
when building a docker image.
However, modification to package.json may happen much more frequently than
we expect, because it does not only contain dependencies, but may also
contain the version number, scripts, and arbitrary configuration for any other
tool.
It's also hard to maintain a Dockerfile that builds a monorepo project, it may look like
FROM node:20
WORKDIR /path/to/somewhere
RUN corepack enable pnpm && corepack install -g pnpm@latest-9
# Files required by pnpm install
COPY .npmrc package.json pnpm-lock.yaml .pnpmfile.cjs ./
# If you patched any package, include patches before install too
COPY patches patches
# for each sub-package, we have to add one extra step to copy its manifest
# to the right place, as docker have no way to filter out only package.json with
# single instruction
COPY packages/foo/package.json packages/foo/
COPY packages/bar/package.json packages/bar/
RUN pnpm install --frozen-lockfile --prod
# Bundle app source
COPY . .
EXPOSE 8080
CMD [ "node", "server.js" ]
As you can see, the Dockerfile has to be updated when you add or remove sub-packages.
pnpm fetch solves the above problem perfectly by providing the ability
to load packages into the virtual store using only information from a lockfile.
FROM node:20
WORKDIR /path/to/somewhere
RUN corepack enable pnpm && corepack install -g pnpm@latest-9
# pnpm fetch does require only lockfile
COPY pnpm-lock.yaml ./
# If you patched any package, include patches before running pnpm fetch
COPY patches patches
RUN pnpm fetch --prod
ADD . ./
RUN pnpm install -r --offline --prod
EXPOSE 8080
CMD [ "node", "server.js" ]
It works for both simple and monorepo projects, --offline enforces
pnpm not to communicate with the package registry as all needed packages are
already present in the virtual store.
As long as the lockfile is not changed, the build cache is valid up to the
layer, so RUN pnpm install -r --offline --prod, will save you much
time.
Options
--dev, -D
Only development packages will be fetched
--prod, -P
Development packages will not be fetched