Caching git heights #801
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Caching git heights #801
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Adds caching of git heights. As calculating the height of repositories with large volumes of commits is expensive, caching the git heights can save time in the following circumstances: - Repetitive invocations of the `GetBuildVersion` msbuild task- e.g. during `dotnet pack`'ing a project, the `GetBuildVersion` task is invoked four times - Incremental versioning- in cases where a cached height is available for older commits, this value will be used avoid the cost of recalculating the entire git height (only new commits will need to be traversed) The caching behavior is enabled by default but can be opted-out by setting the new `NerdbankGitVersioningUseHeightCache` msbuild property to `false` ## Testing ### Automated testing - Verified `GitHeightCache` can serialize + deserialize heights correctly - Verified caching has a measurable impact on performance for cases when there are many commits to traverse - All existing tests pass ### Manual testing Consumed locally-packed version of `Nerdbank.GitVersioning` in a C# project and added ~1500 commits, verifying: - Height caching takes effect on second build, dramatically decreasing build time (~10s -> ~1s) - Adding an additional single commit can leverage the cached version for the previous ~1500 commits but adds the latest - Setting the `NerdbankGitVersioningUseHeightCache` property to `false` bypasses the caching behavior.
…mmits with multiple parents (any cached height would be used and could prevent the relevant commit graph being walked)
…now cached on disk next to the `version.json`/ `version.txt` file in order that performance improvements can be seen by multiple projects.
djluck
reviewed
Dec 9, 2022
| if (versionHeightPosition.HasValue) | ||
| { | ||
| int height = commit.GetHeight(repoRelativeProjectDirectory, c => CommitMatchesVersion(c, baseSemVer, versionHeightPosition.Value, tracker)); | ||
| var cache = new GitHeightCache(commit.GetRepository().Info.WorkingDirectory, versionOptions.RelativeFilePath, baseVersion); |
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We should probably be constructing the git height cache only when useHeightCaching is true.
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Hey @AArnott, apologies for the incredibly slow response- work was incredibly stressful for a period and the idea of finding the time to look through an MR I wrote a good year ago was just too much! So full disclosure: it's been a long time since I've thought about this MR and may not be the most reliable reviewer :) I left a comment on one minor thing I think we could improve. I think we should also provide some updates to the documentation regarding this, informing people about:
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As first seen in #499, which was inadvertently closed prior to merging. Recreating here for review and consideration.
Summary
Adds caching of git heights. As calculating the height of repositories with large volumes of commits is expensive, caching the git heights can save time in the following circumstances:
GetBuildVersionmsbuild task- e.g. duringdotnet pack'ing a project, theGetBuildVersiontask is invoked four timesImplementation details
When can cached results be used?
Opting out
The caching behavior is enabled by default but can be opted-out by setting the new
NerdbankGitVersioningUseHeightCachemsbuild property tofalseCache file
A
version.cache.jsonfile is created per-project with contents that look like this:Testing
Automated testing
GitHeightCachecan serialize + deserialize heights correctlyManual testing
Consumed locally-packed version of
Nerdbank.GitVersioningin a C# project and added ~1500 commits, verifying:NerdbankGitVersioningUseHeightCacheproperty tofalsebypasses the caching behavior.