Use when creating or migrating a Go go.d collector to framework V2, touching CollectorV2, metrix.CollectorStore, ChartTemplateYAML/charts.yaml, charttpl/chartengine, V2 host scopes/vnodes, or V2 collector tests. Focuses on concise maintainer-preferred V2 collector patterns.
Installation
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Use when creating or migrating a Go go.d collector to framework V2, touching CollectorV2, metrix.CollectorStore, ChartTemplateYAML/charts.yaml, charttpl/chartengine, V2 host scopes/vnodes, or V2 collector tests. Focuses on concise maintainer-preferred V2 collector patterns.
Writing Go go.d Modules With Framework V2
Use with project-writing-collectors. Keep this skill loaded for style; read
source files for evidence.
Primary modern example: src/go/plugin/go.d/collector/cato_networks/.
Use focused pieces from it, not the whole collector shape.
Older V2 collectors can still be useful for local patterns, but review them
for stale style before treating them as examples.
Decision Discipline
You MUST aim for the clean end state, not the smallest collector diff. If a
framework capability is missing and the problem is general, design the
framework change instead of hiding the issue in collector-local glue.
If any framework-scope package changes, stop and satisfy
src/go/plugin/framework/docs/changing-framework-code.md before writing code.
You MUST re-check scope after each coherent batch. If the work reveals an
independent collector cleanup, framework fix, or integration-doc change,
either defer it explicitly or land it separately before continuing.
Core Style
New collectors MUST implement collectorapi.CollectorV2 from
src/go/plugin/framework/collectorapi/collector.go and register via
CreateV2.
New() SHOULD own defaults, metrix.NewCollectorStore(), typed metric
instruments, and test seams.
V2 collectors MUST write metrics through metrix.CollectorStore during
Collect() and provide chart template YAML through ChartTemplateYAML();
embedded charts.yaml is RECOMMENDED.
Collect(ctx) MUST return error and write metrics to metrix; it MUST NOT
return a V1 map[string]int64.
Long-running side-effect loops that must start only with the running job MAY
implement optional collectorapi.CollectorV2Runner. Run(ctx) MUST return
promptly after cancellation. Do not start operational polling from Init() or
Check(), because DynCfg test and autodetection use those methods without
starting the runtime job.
Collector Cleanup(ctx) MUST be idempotent. The framework may call it more
than once, including after partial Init / Check setup.
Files SHOULD stay boring: public lifecycle methods in collector.go, setup
helpers in init.go when needed, orchestration in collect.go, distinct
upstream operations in collect_<operation>.go, metrics in metrix.go /
write_metrics.go, focused tests.
Before adding custom HTTP, selector, logging, command-execution, SQL, ping,
or log-file plumbing, check src/go/plugin/go.d/docs/helper-packages.md and
reuse an existing helper when it fits.
If Functions exist, isolate them in a <name>func/ subpackage with a narrow
Deps interface declared there. The Function package MUST NOT import the
collector package or hold *Collector.
If a single-instance collector exposes Creator.SharedFunctions, its
MethodHandler(job) receives the running canonical runtime job and the public
Function shape has no __job parameter. Use job.Collector() to bind the
Function handler to collector-owned state; do not add a package-global
registry to bridge Function dispatch. The Function is still job-backed:
publication waits for the canonical job to be running and available, and
dispatch rejects unavailable jobs before calling MethodHandler.
Shared and instance job-backed Functions are published only while their
backing running jobs are available. By default, every running job is available
for every shared or instance Function. If a collector needs runtime readiness
gating per job-backed Function, implement collectorapi.FunctionAvailability;
keep FunctionAvailable(functionID) cheap and non-blocking.
funcapi.FunctionConfig.Available applies to AgentFunctions, not
job-backed SharedFunctions or InstanceFunctions.
collectorapi.Creator.InstancePolicy defaults to
InstancePolicyPerJob. Use InstancePolicySingle only for collectors that
are intentionally one canonical job per agent. Single-instance configs MUST
use name == module after defaults are applied. DynCfg exposes opted-in
single-instance configs as single objects with the module-level collector
config ID, no collector template, and no add/remove; updates target that
single object.
Before opting in a production collector to InstancePolicySingle, decide how
its initial single object appears in DynCfg. The framework exposes a single
object only after a config exists; it does not publish a template placeholder,
and plain stock enable failures can remove the stock object.
Public config options SHOULD stay small and justified. A proposed config
option MUST name the concrete operator decision it enables; "operators may
want to tune it" is not enough. Internal tuning SHOULD use constants unless
the operator has a real decision to make.
Metrics And Charts
Instruments SHOULD be created once when the metric surface is known.
Use store.Write().SnapshotMeter("") for normal metrics.
Use Vec(...) for labels, Gauge for current values,
Counter.ObserveTotal() for source counters, and StateSet for fixed
one-active-state values.
Metric names MUST be stable and selected by charts.yaml.
In charts.yaml: use version: v1, context_namespace, instances.by_labels,
label_promotion, and an explicit algorithm on every chart:
incremental for counters and absolute for gauges.
Counter.ObserveTotal() only records monotonic values in metrix; it does
NOT set the chart DIMENSION algorithm by itself. Every chart that presents
a counter as a rate MUST explicitly set algorithm: incremental, including
dynamically built charttpl.Chart values.
Do NOT rely on chartengine's metric-name suffix inference for generated
Netdata metrics. Suffix inference is only a fallback and MUST NOT be used as
the correctness mechanism for V2 collector charts.
Histogram bucket charts use range bucket values from metrix.ReadFlatten()
and chartengine forces them to heatmap. Bucket dimensions are named by the
bare le upper-bound value and ordered numerically with +Inf last. Do NOT
add collector-local cumulative-bucket workaround metrics or a bucket-mode
option for V2 charts.
Put multipliers, divisors, hidden flags, and float formatting in the chart
template, not ad hoc chart-emission code.
metrix keeps ONE descriptor per metric NAME, resolved atomically at commit and
BOUNDED: a name idle past its retention window (expireAfterSuccessCycles + descriptorGraceCycles, both configurable on NewCollectorStore(...)) is evicted
and can then re-register with a changed contract. Within that window the
descriptor is authoritative — re-registering a TRULY-LIVE name with a changed
kind / summary quantiles / histogram bounds fails the commit (loud), an idle name
is superseded, and Init-time (out-of-cycle) registration still panics
synchronously on conflict.
If a collector caches per-name handles ACROSS cycles, it MUST NOT keep them for
the job lifetime: couple their lifetime to the descriptor window via the optional
metrix.DescriptorRetention accessor (DescriptorRetentionWindow(),
SuccessfulCommits()), or a stale handle drift-skips a changed-contract name
forever after metrix evicts the descriptor. The prometheus writer
(collector/prometheus/writer.go) is the reference; see
src/go/pkg/metrix/README.md ("Descriptor Lifecycle and Retention").
To reproduce a V1 chart context in a migration, inject context_namespace (the
fixed prefix, or prefix.<app> per job) so autogen rebuilds prefix.<metric> /
prefix.<app>.<metric> without hand-built chart IDs.
When a collector builds its chart template at RUNTIME (not a static charts.yaml):
Emit it with charttpl.Spec.MarshalTemplate() (runs Validate() only, then
marshals with yaml.v2, the decoder's library). Do NOT hand-roll Validate() +
yaml.Marshal, and do NOT marshal with yaml.v3.
If you mutate a charttpl.Group borrowed from a shared profile/catalog, deep-copy
it first with Group.Clone() so per-job edits cannot corrupt the shared template.
A Group you decoded yourself per job is already owned and needs no clone.
Skip empty distributions -- e.g. a summary whose every quantile is NaN -- so a
chart waits for real data, matching how scalar NaN values are already skipped.
For dynamic surfaces whose label sets churn, metrix's Vec handle cache is
unbounded; cache per-series instruments yourself and evict handles unseen for N
cycles to stay bounded. Prefer a framework fix if the need is general
(Decision Discipline).
Compatibility Rules
For V1-to-V2 migrations, start with
src/go/plugin/go.d/docs/migrate-v1-to-v2.md.
Migration Hard Stops
A collector using V1 chart Vars is blocked until framework support, an
approved equivalent design, or explicit breaking-alert approval exists.
collecttest.AssertChartCoverage is not chart-identity parity; it cannot
prove old chart IDs, family, priority, lifecycle, labels, or alert variables.
A finished migration MUST pass an import/runtime-path audit proving no V1
collection path or V1 map-to-metrix bridge remains reachable from normal
execution.
Temporary V1-to-V2 parity bridges MAY be used during development, but the
finished collector MUST NOT keep a runtime V1 map-to-metrix bridge.
For migrations, first create a compatibility manifest covering chart IDs,
contexts, dimension IDs/names, labels, config keys, DynCfg schema keys,
stock config, alerts, docs, and lifecycle behavior.
Migrations MUST preserve existing public contracts unless the SOW records an
explicit breaking decision.
Migrations MUST keep old YAML/JSON field names. Add new config as opt-in when
cardinality, cost, or user-visible identity could surprise existing users.
Collector integration artifacts MUST follow
.agents/skills/integrations-lifecycle/consistency.md; do not preserve a
partial local artifact checklist in V2 collector work.
MUST NOT log raw secrets, DSNs, bearer tokens, or URLs with embedded
credentials.
Hot-Path Logging
Collectors MUST NOT emit Warningf/Errorf every collection cycle for a
recoverable partial failure. Use the built-in logger limiter:
c.Limit("collector:stable-operation-key", 1, time.Hour).Warningf(...).
Limiter keys MUST be stable and low-cardinality. Use operation names, not
entity IDs, labels, URLs, raw errors, or user-controlled values.
Once() is reset by JobV2.runOnce(), so it is useful inside one cycle only;
it is not cross-cycle spam protection.
Full collection failure SHOULD still return an error with context so the job
retry path handles it. Limit only fail-soft warnings/errors where collection
continues with partial or stale data.
Chart Label Identity
Labels used by instances.by_labels or a dimension name_from_label define
chart or dimension identity. Changing one creates a new chart or dimension;
collectors MUST NOT use identity churn merely to refresh metadata.
label_promotion defines non-identity chart metadata. Chartengine reconciles
its effective intersection on existing charts and emits a complete
replacement only when it changes.
Collectors MUST continue publishing numeric samples at their required cadence.
A label-only replacement updates chart metadata; it is not a substitute for
numeric sample-and-hold output.
Host Scopes
Host scopes SHOULD be used only after a product decision says the data belongs
on a generated vnode.
ScopeKey and GUID MUST be deterministic.
Collector-generated vnodes MUST set _vnode_type=<source>.
Host-scope cardinality MUST be bounded and documented. Collectors SHOULD NOT
create VM/disk/NIC/path/sensor scopes by default.
Scope identity MUST use stable IDs. Human-readable names SHOULD be hostnames
or promoted labels only.
Tests
At minimum, V2 work MUST include these tests, or the PR/SOW MUST justify why a
specific item does not apply:
config YAML/JSON serialization compatibility;
Init, Check, Collect, and Cleanup lifecycle coverage;
explicit metric-store cycle tests with BeginCycle, success commit, and abort
on expected collection errors;
chart coverage assertions for fixtures expected to materialize all dimensions;
host-scope tests when scopes/vnodes are used.
Pre-PR Check
A finished V1-to-V2 migration MUST NOT keep a runtime
map[string]int64 collection path or V1 map-to-metrix bridge.
The PR description or design note MUST enumerate affected collector
consistency artifacts and justify every artifact that did not need a matching
change. SHOULD-level exceptions and escape hatches MUST be reviewer-visible.
Existing public chart/metric/config identity MUST be preserved unless the SOW
records an explicit breaking decision.
New labels and scopes MUST be bounded and documented.
Enrichment SHOULD be split from the V2 compatibility migration when possible.
