# Agent instructions

Follow [`CONTRIBUTING.md`](CONTRIBUTING.md) for all changes. These instructions
apply throughout the repository; also read any `AGENTS.md` in the area you edit.

## Project and source map

`windows_exporter` is a Go Prometheus exporter for Windows. Most collectors and
native bindings require Windows; a successful cross-build does not validate
their runtime behavior.

- [`cmd/windows_exporter`](cmd/windows_exporter): executable, flags, process
  settings, Windows service startup and shutdown.
- [`pkg/collector`](pkg/collector): collector registration, configuration,
  initialization, filtered views, scrape scheduling and resource ownership.
- [`internal/collector`](internal/collector): built-in collectors. Each implements
  `GetName`, `Build`, `Collect` and `Close` from
  [`pkg/collector/types.go`](pkg/collector/types.go).
- [`internal/pdh`](internal/pdh):
  performance counter queries. [`internal/mi`](internal/mi)
  provides Management Infrastructure queries; [`internal/ole`](internal/ole) and
  [`internal/headers`](internal/headers) contain native Windows bindings.
- [`internal/config`](internal/config), [`internal/httphandler`](internal/httphandler)
  and [`internal/log`](internal/log): YAML/CLI configuration, HTTP scraping and
  logging.
- [`docs/collector.<name>.md`](docs): collector flags, metric names, types, labels
  and examples. [`docs/collector-template.md`](docs/collector-template.md) is the
  documentation template.
- [`contrib/mixin`](contrib/mixin): Jsonnet recording rules, alerts and dashboard
  sources. [`dashboard`](dashboard) contains the generated Grafana dashboards;
  [`docs/runbooks`](docs/runbooks) documents the alerts.
- [`installer`](installer), [`kubernetes`](kubernetes) and [`tools`](tools): MSI
  packaging, deployment examples, CI fixtures and end-to-end helpers. The CI
  package job validates installer changes with
  [`tools/test-installer.ps1`](tools/test-installer.ps1), which installs the
  service for real. Never run it on a developer machine. Never upgrade from a
  0.31.x package there: its `taskkill /T` follows stale parent process IDs and
  can kill the runner agent, which fails the job with "The hosted runner lost
  communication with the server" and no logs.
- Release builds give the executable and the MSI a numeric four-part version
  computed in the CI build job (`output/FILE_VERSION`): the fourth field is N
  for `alpha.N`/`beta.N`, 100+N for `rc.N` and 1000 for the release, so MDM
  tools that compare file versions update from one beta to the next and to the
  final release. Windows Installer itself ignores the fourth field.

New collectors need discussion with maintainers first. Prefer the configurable
`performancecounter` collector where it can provide the requested metrics, as
described in `CONTRIBUTING.md`.

## Development and checks

Use the Go version specified in [`go.mod`](go.mod) and the linter version pinned
in [`Makefile`](Makefile). Do not change versions to work around a local tooling
problem. Follow [`.golangci.yaml`](.golangci.yaml), [`.editorconfig`](.editorconfig)
and [`.gitattributes`](.gitattributes); keep LF line endings and the existing
license headers. Use structured `slog` attributes and the existing Windows API
wrappers (`golang.org/x/sys/windows`, `NewLazySystemDLL`). `LazyProc.Call`
panics for a missing export: add every proc a binding calls without its own
`Find` check to the package's `lazyproc.Once` list, and call the package's
`Load` in the `Build` of each collector that uses it. Mirrors of native structs
that MI or COM read by offset need `unsafe.Sizeof`/`Offsetof` checks, see
[`internal/mi/layout.go`](internal/mi/layout.go).

Before committing, run the repository checks from its root:

```sh
make fmt
make lint
make test
```

If GNU Make is unavailable on Windows, use the equivalent commands from the
current Makefile. Its current formatter and linter commands are:

```powershell
go run github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.14.0 fmt
go run github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.14.0 run ./...
go test ./...
```

Release builds apply a `go build -overlay` from
[`tools/go-overlay`](tools/go-overlay/main.go) that removes the 32 MiB FIPS
140-3 entropy buffer Go links into every binary (golang/go#81956). It is pinned
to the checksum of the patched standard library file, so a Go update that
changes that file fails the build job until the overlay is refreshed or, once Go
fixes the issue, removed. Plain `go build` and `make build` do not apply it.

For collector or concurrency changes, also run the affected packages natively
on Windows with `go test -race -count=1 -timeout=10m <packages>`. Add regression
tests for behavior changes and benchmarks for performance improvements. Check
actual emitted metric values, types and labels through registry gathering;
configuration or struct assertions alone do not prove publication is correct.

Read [`docs/ci-testing.md`](docs/ci-testing.md) before changing fixtures or test
skip rules. `WINDOWS_EXPORTER_TEST_COLLECTORS` lists collectors provisioned by CI;
their failures must fail tests. Optional roles may be absent locally. Report
skipped coverage and checks blocked by missing tools, permissions, services or
network access in the PR. Do not claim that cross-compilation or a fixture test
exercised a live Windows role.

## Collector implementation rules

- Preserve metric names, label sets, types, units, defaults and configuration
  compatibility unless the change intentionally updates that contract. Update
  the corresponding collector documentation and affected queries together.
  Follow existing deprecation patterns when replacing published metrics.
- Determine metric types per counter, using `pdh.Collector.MetricType` where
  appropriate. Raw PDH values can be cumulative numerators, ticks or counts,
  even when the Windows counter name says average, percentage or seconds.
  Convert units explicitly; expose the base/operation count needed for ratios.
  The raw value of a `PERF_AVERAGE_TIMER` counter is in ticks of its time
  base: in new code, divide it by `pdh.Collector.Frequency` instead of a fixed
  factor. The disk and `smbclient` collectors still use the fixed 1e-7
  (10 MHz) factor.
  Never publish an invalid sample as zero: that can look like a counter reset.
- Keep the typed PDH collectors and `perfdata` tags. Preserve duplicate
  instance occurrences within a sample; their suffixes are not stable identities.
  Do not remove every name ending in `_Total`: legitimate process and database
  names can use that suffix. Use the shared aggregate-instance policy.
  `pdh.Collector.Collect` reuses the backing array of its destination slice
  and `Row.Values`; do not keep rows, sub-slices or pointers into it across
  scrapes.
- PDH collectors add counters by English path. On a Windows installation
  without en-US resources, the 009 name table holds localized names for v2
  (manifest-based) counter sets such as `SMB Server Shares` or `HTTP Service`;
  `internal/pdh/localized.go` then maps the English names through the v2
  registration API. Classic (v1) sets such as `Processor` are not affected.
- Keep `Build`, `Collect` and `Close` serialized for each collector instance.
  Filtered `WithCollectors` views share execution state and do not own shutdown;
  the original `Collection` owns collectors and MI resources. A timed-out call
  may still be running: prevent overlap, drain late metrics and do not free its
  resources while it runs. Honor the supplied scrape budget in blocking APIs.
  `Build` has no budget: bound its MI probe queries with `mi.BuildQueryTimeout`,
  never `0` (no MI timeout), so one stalled provider cannot block startup.
- Collectors that reuse metrics or label pairs between scrapes keep an
  `internal/metriccache` or `internal/labelcache` field and list it in
  `ScrapeCaches()` (`internal/scrapecache`). The collection resets these caches
  before `Build` and after `Close`, and begins a scrape before and ends it after
  each `Collect`; `Collect` gets it with `Scrape()`. Do not call `Begin`,
  `Commit` or `Reset` in collectors. A direct `Collect` call, as in most tests,
  runs without the caches; use `testutils.Collect` or `scrapecache.Begin` to
  test the cached path.
- Release resources after partial initialization and on error paths. A non-nil
  PDH collector returned with an error still belongs to the caller and must be
  closed. Sub-collector cleanup closures must read the initialized field when
  called; method values captured before initialization can retain nil receivers.
  Stop background workers before releasing the resources they use, and recover
  panics inside the goroutine that can panic.
- Inspect every independent cause in joined errors. An expected no-data or
  unsupported-subsystem error must not hide an unrelated failure. Preserve valid
  metrics from successful parts of a scrape and the existing child-success
  metrics for collectors with sub-collectors.
- Match native function signatures, struct layouts and buffer-size units to the
  Windows API contract. Query required buffer sizes safely and retry when they
  grow. Distinguish bytes from UTF-16 characters, signed integers from bit
  patterns, and MI NULL values from populated unions. Respect borrowed/owned
  pointers, allocator-specific cleanup and COM thread initialization; use the
  native COM helpers rather than restoring the removed `go-ole` dependency.
- Keep CLI and YAML validation consistent. Reject unknown fields, unsupported
  sub-collector names and invalid values; preserve CLI precedence and repeated
  flag/list behavior. Changes to config shapes also need schema, flag parsing
  and documentation updates. A collector is registered once, in the
  `registrations` table of `pkg/collector/map.go`, with a `Config` field whose
  YAML key is the collector name and a `docs/collector.<name>.md`;
  `TestRegistrations` checks that they agree. The configuration file schema in
  `internal/config` only checks keys: the flags parse and validate the values.
  Register include/exclude expression flags with `utils.RegexpFlag`, which
  anchors the expression, stores the compiled `*regexp.Regexp` in the config
  and names the flag in parse errors; use `utils.IsMatchAll`/`IsMatchNone` to
  detect unfiltered defaults.
- For textfiles, keep HELP/type metadata consistent across files and preserve
  unrelated valid series when reporting duplicates or parse failures. Publish
  producer output by replacing a temporary file in the same directory. File
  mtime indicates accepted input; a producer's last-success timestamp indicates
  data freshness. Use emitted exporter/collector signals in alert examples.

These rules draw on the latest 150 PRs reviewed for this guide (#2451 through
#2602, including open and closed proposals). Representative merged changes are
[scrape lifecycle #2541](https://github.com/prometheus-community/windows_exporter/pull/2541),
[filtered ownership #2587](https://github.com/prometheus-community/windows_exporter/pull/2587),
[PDH types and validity #2543](https://github.com/prometheus-community/windows_exporter/pull/2543),
[MI return values #2537](https://github.com/prometheus-community/windows_exporter/pull/2537),
[native COM #2551](https://github.com/prometheus-community/windows_exporter/pull/2551)
and [joined collection errors #2574](https://github.com/prometheus-community/windows_exporter/pull/2574).
Check the current source and PR status before treating an open proposal as
implemented behavior.

## Live exporter validation

The development environment may already have an exporter running at
`http://localhost:9182`. Check availability and `windows_exporter_build_info`
before using it as a baseline; it may have a different revision, configuration
or enabled collector set from your checkout.

```powershell
(Invoke-WebRequest -Uri 'http://localhost:9182/metrics' -TimeoutSec 30).Content
(Invoke-WebRequest -Uri 'http://localhost:9182/metrics?collect[]=cpu' -TimeoutSec 30).Content
```

Inspect `windows_exporter_collector_success`,
`windows_exporter_collector_duration_seconds`,
`windows_exporter_collector_timeout` and `windows_exporter_scrape_queue_timeout`
(the scrape timed out waiting for an earlier scrape, so no collector ran), plus the
affected metric families. HTTP 200 alone does not mean every collector succeeded. PDH rate counters need a second
sample after initialization.

To validate changed code, build a separate executable and run it on an unused
port with the relevant collectors, then scrape it from another shell:

```powershell
go build -o windows_exporter.dev.exe ./cmd/windows_exporter/
.\windows_exporter.dev.exe --web.listen-address=127.0.0.1:9183 --collectors.enabled=cpu
```

Adjust the collector list for the change. Leave the existing exporter instance
running unless the user requests changes to it.

To check a collector's metric types against Windows, list each counter of the
PDH object with its type and raw value. Windows PowerShell 5.1 can do this
through .NET; `RawValue` and `BaseValue` are what `pdh.CounterTypeRaw` returns
as first and second value:

```powershell
$cat = [System.Diagnostics.PerformanceCounterCategory]'DirectoryServices'
$cat.GetCounters('NTDS') | ForEach-Object {
    $s = $_.NextSample()
    '{0} | {1} | raw={2} base={3}' -f $_.CounterName, $_.CounterType, $s.RawValue, $s.BaseValue
}
```

Every PDH-based collector except `exchange`, `smtp` and `vmware` has such a
dump in the `AGENTS.md` of its directory, including roles that are rarely
available on development machines (AD DS, AD CS, AD FS, DFSR, Hyper-V, IIS,
SQL Server, NPS, RemoteFX sessions). Check a type or unit question there
first.

## Dashboards, rules and runbooks

Read [`contrib/mixin/README.md`](contrib/mixin/README.md) and
[`dashboard/README.md`](dashboard/README.md) before editing monitoring artifacts.
Edit the Jsonnet/Grafonnet source under `contrib/mixin/dashboards`, including its
tab modules and shared builders, and regenerate `dashboard/windows-exporter-*.json`:
the full dashboard `windows-exporter-dashboard.json` and one dashboard per tab.
Do not hand-edit generated JSON. Tab dashboards keep only the variables their
panels reference, so reference variables as `$name` or `${name}`.
Gate every tab, row, panel and variable on the collectors it queries with
`on('<collector>')` (names from `_config.collectors`), and run
`jsonnet -J vendor tests/dashboard.test.jsonnet` to check the layout for several
collector selections.

From `contrib/mixin`, install the tools pinned in `mise.toml` with
`mise install`, then run `mise run fmt`, `mise run generate`,
`mise run check-dashboards` and `mise run test`. Keep generated artifacts in
sync. The tests cover Jsonnet format, dashboard parity, promtool rules/tests,
offline pint lint, dashboard lint and runbook coverage.

The tasks are POSIX shell scripts (`set -eu`, `trap`, `mktemp`, `$(...)`) that
also call `rm`, `cp`, `diff`, `git` and, for `check-runbooks`, `python3`. On
Windows, mise runs inline tasks with `cmd /c` by default, so run them in WSL, or
from Git Bash with `MISE_WINDOWS_DEFAULT_INLINE_SHELL_ARGS="bash -c"` and Git's
`bash` (not `C:\Windows\System32\bash.exe`, which starts WSL) first on `PATH`.

Without mise, run the Jsonnet tools with `go run` at the versions pinned in
`mise.toml`, for example
`go run github.com/google/go-jsonnet/cmd/jsonnet@v0.22.0` (also `jsonnetfmt`
and `jsonnet-lint`) and
`go run github.com/jsonnet-bundler/jsonnet-bundler/cmd/jb@v0.6.0 install`. That
covers formatting, generation and the Jsonnet tests; promtool, pint and
dashboard-linter still need their release binaries, so report those checks as
skipped. A Windows checkout with `core.autocrlf` has CRLF sources, so compare
generated output with `diff --strip-trailing-cr`.

`go test ./internal/metriccontract/` checks that every `windows_` metric name
in the readme files, `docs/collector.*.md`, the runbooks, the mixin and the
dashboards is created by a collector; it reads the Go sources, so it also runs
on Linux. When documentation names a renamed or removed metric on purpose, add
it to `historicalReferences` in that test with the reason.

Preserve target/device labels, apply counter rates before aggregation, and
handle zero denominators. Keep optional-role alerts configurable and provide a
runbook for each alert. Check required collector availability and the Grafana
version documented by the dashboard.

## Pull requests

Branch from current upstream `main`, keep commits focused and sign off each
commit with `git commit -s` for the DCO. Preserve unrelated local changes; use a
separate worktree when needed. Follow [`.github/PULL_REQUEST_TEMPLATE.md`](.github/PULL_REQUEST_TEMPLATE.md)
and use the `subsystem: description` title format required by
[`CONTRIBUTING.md`](CONTRIBUTING.md) and
[`.github/workflows/pr-check.yaml`](.github/workflows/pr-check.yaml).
Explain the problem, resulting behavior and validation, including any limits.

## Pull request labels

Before merging, apply at least one label from [`.github/release.yml`](.github/release.yml):

- `💥 breaking-change`: breaking changes
- `✨ enhancement`: user-visible functionality
- `🐞 bug`: fixes
- `🛠️ dependencies`: dependency updates
- `📖 docs`: documentation
- `chore`: internal performance work, tests, CI, or maintenance

Add `💥 breaking-change` alongside any other applicable label. Labeling is an
AI-agent-only operation; do not tell external contributors to apply labels.

Keep this guide accurate when an authorized change reveals a useful repository
convention or pitfall. Put detailed component guidance in a scoped `AGENTS.md`
when needed, and keep `CLAUDE.md` as a pointer to the shared instructions.