The Gerrit User Summit 2019 presented updates and new features in Gerrit 3.1, including migration paths, performance improvements, and enhanced Git protocol v2. Future development plans were outlined for Gerrit 3.2, focusing on authentication, performance upgrades, and advanced integrations. Key highlights included breaking changes, new plugins, and upcoming enhancements to increase usability and efficiency.

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Gerrit User Summit 2019 – GerritForge Inc – Sunnyvale CA GerritForge.com 0
What’s new in Gerrit 3.1
… and beyond
Luca Milanesio
Gerrit Code Review Maintainer
GerritForge

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Gerrit User Summit 2019 – GerritForge Inc – Sunnyvale CA GerritForge.com 1
About GerritForge
Founded in
the UK
HQ in
London
Committed to
OpenSource
+ Sunnyvale
CA

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Gerrit User Summit 2019 – GerritForge Inc – Sunnyvale CA GerritForge.com 2
Gerrit v3.1 in numbers
Source: analytics.gerrithub.io

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Migration path to v3.1
• v2.14 / ReviewDb
• v2.15 / ReviewDb
• v2.16 / ReviewDb
• v2.16 / NoteDb
•v3.0
•V3.1 https://www.workeastren.co.uk/case-studies/paul-steps-to-success-case-study/

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New non-core plugins
Checks (Native CI integration, yeah!)
Multi-site (!!!)
Pull-replication
Zookeeper (global ref consistency)

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What’s new in v3.1
Polymer 2.0 and shadow DOM
Git Protocol v2 (secured)
Performance improvement and logging
Stability and Fixes
More CI integration (checks plugin)

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Git protocol v2
From https://opensource.googleblog.com/2018/05/introducing-git-protocol-version-2.html
• Server-side filtering of references
• Easy extensibility for new features

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Git protocol v2: server-side filtering
From https://opensource.googleblog.com/2018/05/introducing-git-protocol-version-2.html
• Previously: servers responded to all fetch commands with an initial reference
advertisement, listing all references in the repository.
• Sent even when a client only cares about updating a single branch
• Chromium repository (over 500k refs): the server is sending 10s of megabytes of data
that get ignored.
• Projects have seen a performance improvement of 3x for no-op fetches of a single
branch on repositories containing 500k references.

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Git protocol v2: done in 3 attempts
See https://groups.google.com/d/topic/repo-discuss/nEkvNVCZzNM/discussion
• v2.16 and v3.0 reverted attempted, because of security vulnerability issues
• Patrick (Google) created PermissionAwareRefDatabase, permission aware repository
abstraction, that will only ever return refs that the user has access to.
• Then Stefano (GerritForge) took over this change and fixed some problems
• Adjustments in JGit, Thanks for review to Matthias (SAP)
• The whole series in Gerrit was reviewed by Han Wen (Google), Thanks!

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Git protocol v2: how we tested it
In context of the third attempt to enable Git wire protocol v2 in Gerrit:
• Start the whole nine yard Gerrit server using StandaloneSiteTest base class
• Retrieve both SSH and HTTP ports assigned during server start
• Configure SSH private/public keys for SSH access and upload them to Gerrit using
plugin API
• Configure HTTP passwords for test users using Gerrit plugin API
• Access Gerrit server with git-core client using Java's ProcessBuilder facility

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Git protocol v2: how to enable it
In context of the third attempt to enable Git wire protocol v2 in Gerrit:
<gerrit-site>/etc/jgit.config
[protocol]
version = 2
* Verify that recent Git client is installed (v2.18 or later):
$ git --version
git version 2.23.0
* Activate protocol.version 2 in ~/.gitconfig
* Demo Git protocol v2:
$ GIT_TRACE_PACKET=1 git ls-remote https://review.gerrithub.io/GerritCodeReview/bazlets
07:59:25.849401 pkt-line.c:80 packet: git< version 2

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Breaking changes in v3.1
Push to refs/drafts/* removed
Push to refs/changes/* removed

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Breaking changes in v3.1
JGit config read from
$GERRIT_SITE/etc/jgit.config
(bye bye ~/.gitconfig)

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Roadmap to Gerrit v3.2 and beyond
• Pluggable authentication backends
• Group deletion
• Polymer 3
• Introduction of the ”attention set” instead of
assignee
• Robot comments
• Support for apply/fix feature

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Roadmap to Gerrit v3.2 and beyond
• Performance improvements
• Git push performance
• PolyGerrit UI latency
• Gerrit caches with caffeine
• Repos with large number of refs (experimental: reftable)
• Faster persistent cache than H2
• Support for large mono-repos
• Support for Java 11
• Better GC algorithm: ZGC
• Support for very large heaps (up to TBytes of memory)

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Roadmap to Gerrit v3.2 plugins
• Replication plugin
• Multi-master support
• External replication queue
• Checks plugin
• Support for sub-checks
• Override status
• High-availability plugin
• Integration with global ref-db
• Multiple concurrent writes on all nodes

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Q&A: excited about the future of Gerrit?
Image from: http://cypp.rutgers.edu/ru-voting/political-information/public-opinion-polls/

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