feat: increase Drain tree depth from 4 to 30

[STRRL]

Matches Loki's default (LogClusterDepth: 30). Higher depth means the prefix tree routes more precisely, reducing the number of candidate clusters that need similarity comparison at leaf nodes.

Ref: https://github.com/grafana/loki/tree/main/pkg/pattern/drain

[gemini-code-assist]

Summary of Changes

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This pull request improves the precision of log clustering by adjusting the Drain tree depth to match Loki's default configuration. By increasing the tree depth, the prefix tree can route log messages more accurately, which in turn reduces the number of candidate clusters that require similarity comparisons at the leaf nodes, leading to more efficient and precise log pattern identification.

Highlights

• Drain Tree Depth Configuration: The drain3.WithDepth parameter in the NewDrainParser function has been increased from 4 to 30. This change aligns the depth with Loki's default LogClusterDepth.

Changelog

• pkg/pattern/drain.go
  • Updated the drain3.WithDepth parameter from 4 to 30 within the NewDrainParser function.

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[gemini-code-assist]

Code Review

This pull request increases the Drain tree depth from 4 to 30, aligning it with Loki's default value. This is a sensible change to improve log pattern clustering precision. My review includes a suggestion to refactor the hardcoded parameters in NewDrainParser into named constants. This will improve code readability and maintainability, and also resolve an existing issue of duplicated code for delimiters within the package.

[gemini-code-assist]

While changing the depth, this is a good opportunity to address the magic numbers in this block of parameters. The values 30, 0.4, and the delimiter slice are hardcoded. Defining them as named, package-level constants/variables would improve readability and maintainability.

Additionally, the delimiter slice []string{"|", "=", ","} is duplicated in pkg/pattern/parser.go. This should be defined in one place to avoid inconsistencies.

I suggest defining these at the package level:

const (
	// defaultDrainDepth matches Loki's default LogClusterDepth.
	// Ref: https://github.com/grafana/loki/tree/main/pkg/pattern/drain
	defaultDrainDepth = 30
	defaultDrainSimTh = 0.4
)

// drainExtraDelimiters is also used in parser.go and should be the single source of truth.
var drainExtraDelimiters = []string{"|", "=", ","}

Then, the NewDrain call would be cleaner and safer:

d, err := drain3.NewDrain(
	drain3.WithDepth(defaultDrainDepth),
	drain3.WithSimTh(defaultDrainSimTh),
	drain3.WithExtraDelimiter(drainExtraDelimiters),
)

This would also require updating pkg/pattern/parser.go to use the new shared drainExtraDelimiters variable.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Revert Drain depth increase that fragments clusters

Increasing WithDepth from 4 to 30 causes Drain to branch on many more leading tokens before similarity matching, so messages that differ in an early non-numeric field (for example token 3–10) are routed to different leaves and never compared as one template. In this repo that is a functional regression because runDrain keeps only clusters with Count > 1 (cmd/lapp/workspace.go:311-314), so the extra singleton clusters are dropped from semantic labeling and pushed into unmatched output, reducing pattern recall for real logs.

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