feat: add sum aggregator to support summing numeric values

[kazeburo]

PR Type

Enhancement, Tests, Documentation

---

Description

• Add sum aggregation for numeric JSON values.

• Apply numeric modifiers and duration-based output scaling.

• Test accumulation alongside existing aggregators.

• Document usage and supported modifiers.

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Diagram Walkthrough

flowchart LR
  input["Numeric JSON value"]
  parse["Parse as float"]
  total["Accumulate sum"]
  output["Apply modifiers and duration scaling"]
  input -- "extract" --> parse
  parse -- "add" --> total
  total -- "emit metric" --> output

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File Walkthrough

	Relevant files
Enhancement	main.go Advertise sum aggregation in command-line help                      cmd/mackerel-plugin-jsonl/main.go List sum among supported CLI aggregators. +1/-1      percentile.go Recognize sum in aggregator option parsing                              cmd/mackerel-plugin-jsonl/percentile.go Accept sum as an aggregator name. +1/-1      reader.go Accumulate and emit duration-scaled sum metrics                    cmd/mackerel-plugin-jsonl/reader.go Accumulate parsed numeric values in a sum field. Restrict string modifiers and initializers for sum. Apply numeric modifiers and duration scaling when emitting sum metrics. +18/-2
Tests	parser_test.go Test sum accumulation with existing aggregators                    cmd/mackerel-plugin-jsonl/parser_test.go Parse 100 records and verify their numeric sum. Check count, grouping, and percentile behavior alongside sum. +28/-14
Documentation	README.md Document sum aggregation and modifier compatibility            README.md Document sum usage and an example metric. Include sum in multiply support and clarify modifier restrictions. +6/-5

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

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⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪

🧪 PR contains tests

🔒 No security concerns identified

⚡ No major issues detected

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Benchmark Comparison

Base: main
PR: feat/sum-aggregator

BenchmarkMainParse results

goos: linux
goarch: amd64
pkg: github.com/monitoring-forge/mackerel-plugin-jsonl/cmd/mackerel-plugin-jsonl
cpu: Intel(R) Xeon(R) Platinum 8370C CPU @ 2.80GHz
                             │ base-bench.txt │            pr-bench.txt            │
                             │     sec/op     │   sec/op     vs base               │
MainParse_jsonl-4                30.46m ± 19%   32.24m ± 1%  +5.84% (p=0.023 n=10)
MainParse_jsonl_eachkey-4        37.86m ±  1%   38.47m ± 1%  +1.61% (p=0.000 n=10)
MainParse_parse_and_output-4     31.76m ±  1%   33.88m ± 1%  +6.68% (p=0.000 n=10)
geomean                          33.21m         34.76m       +4.69%

                             │ base-bench.txt │            pr-bench.txt             │
                             │      B/op      │     B/op      vs base               │
MainParse_jsonl-4                4.642Mi ± 0%   4.642Mi ± 0%       ~ (p=0.448 n=10)
MainParse_jsonl_eachkey-4        4.642Mi ± 0%   4.642Mi ± 0%  +0.00% (p=0.000 n=10)
MainParse_parse_and_output-4     5.412Mi ± 0%   5.412Mi ± 0%  +0.00% (p=0.000 n=10)
geomean                          4.886Mi        4.886Mi       +0.00%

                             │ base-bench.txt │            pr-bench.txt            │
                             │   allocs/op    │  allocs/op   vs base               │
MainParse_jsonl-4                 100.4k ± 0%   100.4k ± 0%       ~ (p=0.598 n=10)
MainParse_jsonl_eachkey-4         100.4k ± 0%   100.4k ± 0%       ~ (p=0.474 n=10)
MainParse_parse_and_output-4      100.5k ± 0%   100.5k ± 0%       ~ (p=0.635 n=10)
geomean                           100.4k        100.4k       -0.00%