perf(docker): improve pd/store/server image build cache efficiency

[bitflicker64]

Purpose of the PR

close #2977

Main Changes

.dockerignore (new file)

• Minimal, intentionally lean — only Docker-specific extras (.git, .github, compose files, docs)
• Most patterns already covered by .gitignore, not duplicated per maintainer guidance

All 4 Dockerfiles

• Added COPY --parents **/pom.xml ./ before COPY . . — pom layer only invalidates on pom changes, not source changes
• Added --mount=type=cache,target=/root/.m2 on mvn package — deps cached across repeated builds
• Removed vim, cron, service cron start, rm /var/lib/dpkg/info/libc-bin.*, dead code from runtime stage

Note: dependency:go-offline not used — inter-module deps like hg-pd-client aren't on Maven Central and would cause it to fail.

Verifying these changes

• Need tests and can be verified as follows:

docker build -f hugegraph-pd/Dockerfile -t hugegraph-pd:cache-test .
docker build -f hugegraph-store/Dockerfile -t hugegraph-store:cache-test .
docker build -f hugegraph-server/Dockerfile -t hugegraph-server:cache-test .
docker build -f hugegraph-server/Dockerfile-hstore -t hugegraph-server-hstore:cache-test .

Does this PR potentially affect the following parts?

• Dependencies (add/update license info & regenerate_known_dependencies.sh)
• Modify configurations
• The public API
• Other affects (typed here)
• Nope

Documentation Status

• Doc - No Need

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 1.56%. Comparing base (e108076) to head (4cc2e42).

❗ There is a different number of reports uploaded between BASE (e108076) and HEAD (4cc2e42). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (e108076)	HEAD (4cc2e42)
	3	2

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #3025       +/-   ##
============================================
- Coverage     35.85%   1.56%   -34.30%     
+ Complexity      338      43      -295     
============================================
  Files           802     780       -22     
  Lines         67995   65480     -2515     
  Branches       8902    8454      -448     
============================================
- Hits          24381    1026    -23355     
- Misses        41008   64368    +23360     
+ Partials       2606      86     -2520     

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[Copilot]

Pull request overview

This PR aims to improve Docker build cache efficiency for HugeGraph PD, Store, and Server images by adding Docker context filtering and BuildKit/Maven cache-related Dockerfile changes.

Changes:

• Adds a new root .dockerignore.
• Updates four Dockerfiles to use a pom-only copy layer and Maven cache mounts.
• Removes some runtime packages and cleanup/startup commands from image build stages.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 15 comments.

Show a summary per file

File	Description
.dockerignore	Adds Docker build-context exclusions.
hugegraph-pd/Dockerfile	Refactors PD image build layers and runtime dependency install.
hugegraph-store/Dockerfile	Refactors Store image build layers and runtime dependency install.
hugegraph-server/Dockerfile	Refactors Server image build layers and runtime dependency install.
hugegraph-server/Dockerfile-hstore	Refactors hstore Server image build layers and runtime dependency install.

---

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[imbajin]

Direction is right but a few blockers remain. See inline for net-new findings; +1'd Copilot's threads on the labs syntax / pom-only layer / root-pom glob (those are correct). Body-level: README/BUILDING should also note the new BuildKit ≥ 0.20 requirement, and removing vim is a behavioral change worth calling out in the commit body for ops folks who exec into containers.

[imbajin]

‼️ The premise here is incorrect — Docker's build context exclusion does not inherit .gitignore. As a result, locally-extracted release dirs (apache-hugegraph-*/, measured at ~790 MB on a normal dev checkout), .idea/, node_modules/, logs/, *.iml, *.class, gen-java/, upload-files/, .vscode/, *.tar.gz, dist/, build/ all leak into every build's context, defeating the cache work in this PR (and risking IDE / secret leakage into image layers).

Suggested change

	# covered by .gitignore. Only Docker-specific extras are listed here.
	**/target/
	# IMPORTANT: .dockerignore does NOT inherit .gitignore — patterns must be restated.
	# Pre-extracted release dirs / archives
	apache-hugegraph-*/
	**/*.tar
	**/*.tar.gz*
	**/*.zip
	**/*.war
	# IDE / OS
	.idea/
	.vscode/
	**/*.iml
	**/*.iws
	**/.DS_Store
	# Build / runtime artifacts
	**/logs/
	**/*.log
	**/*.class
	**/gen-java/
	**/upload-files/
	**/dist/
	**/build/
	**/node_modules/
	# Env files
	.env.local
	.env.*.local
	# Git internals
	.git
	.gitignore
	.gitattributes
	.github
	# Compose / docs not needed in build context
	**/docker-compose*.yml
	**/docker-compose*.yaml
	**/*.md
	docs/

[imbajin]

⚠️ Two concerns on this line:

1. Scope creep: bumping ubuntu-22.04 → ubuntu-latest is unrelated to the Docker cache work in this PR. The original # TODO was a deliberate guard (Ubuntu 24.04 changed default Java, removed legacy packages). Suggest reverting in this PR and splitting into a focused follow-up.
2. ubuntu-latest drifts when GitHub flips the alias — pin explicitly:

Suggested change

	runs-on: ubuntu-latest
	runs-on: ubuntu-24.04

Flagging here since it's the only CI file touched: there is no CI workflow that exercises any Dockerfile (verified — zero docker build references under .github/workflows/). PR's verification is "run docker build locally". Future regressions will ship silently. Consider adding a build-only smoke job:

docker-build:
  runs-on: ubuntu-24.04
  strategy:
    matrix:
      dockerfile:
        - hugegraph-pd/Dockerfile
        - hugegraph-store/Dockerfile
        - hugegraph-server/Dockerfile
        - hugegraph-server/Dockerfile-hstore
  steps:
    - uses: actions/checkout@v4
    - uses: docker/setup-buildx-action@v3
    - run: docker buildx build -f ${{ matrix.dockerfile }} --load .

[imbajin]

🧹 Pre-existing issue (not a regression from this PR, but worth fixing while in the area): the cron package stays installed in the runtime image (~3 MB), but no cron daemon is ever started — dumb-init only execs docker-entrypoint.sh. This means start-hugegraph.sh -m true silently fails to fire its scheduled monitor job, even though crontab_append returns success. Either:

• Drop cron entirely (saves ~3 MB and removes the false impression that monitor mode works), or
• Start cron in docker-entrypoint.sh (cron & before the server start) so the feature actually works.

Same applies to Dockerfile-hstore and the PD / Store Dockerfiles.