mesh-catalog/modules/mesh-self-check/cmd/mesh-self-check/observation.go

package main

// What a probe observes, and the finding it is written as (novox/hq ADR 0564 §2). A probe says what it sees as an
// Observation, the controller's observation: its token, its evidence in one line, and whether one look can be wrong
// about it. It is written into the bucket `findings` as mesh-sdk's health.Finding, whose key is the controller's key
// for the same condition, so the condition the keeper raises from it and the one the controller raised share one key.

import (
	"encoding/json"
	"time"

	"git.novox.be/novox/mesh-sdk/go/health"
)

// The severities and scopes, as mesh-sdk's health names them.
const (
	Urgent     = health.Urgent
	Warning    = health.Warning
	ScopeBus   = health.ScopeBus
	ScopeCore  = health.ScopeCore
	ScopeProbe = health.ScopeProbe
	ScopeMesh  = health.ScopeMesh
)

// Subject is what a finding is about.
type Subject = health.Subject

// Observation is one thing a probe sees wrong now.
type Observation struct {
	Kind        string
	Token       string
	Subject     Subject
	Severity    health.Severity
	Summary     string
	Said        string
	Headline    string
	Explanation string
	Resolved    string
	Needs       string
	// Source is the probe that saw it, or the self-check itself for a probe that could not run.
	Source string
	// Confirm says one look can be wrong about it: written only when two runs in a row see it (issue 277).
	Confirm bool
}

// Key is where it is kept: `<scope>.<id>.<token>`, the controller's key for the same condition.
func (o Observation) Key() string {
	token := o.Token
	if token == "" {
		token = o.Kind
	}
	return health.Key(o.Subject.Scope, o.Subject.ID, token)
}

// Finding is the observation as written by run at, its evidence the one line it said.
func (o Observation) Finding(run string, at time.Time) health.Finding {
	f := health.Finding{Key: o.Key(), Kind: o.Kind, Subject: o.Subject, Severity: o.Severity, Summary: o.Summary,
		Headline: o.Headline, Explanation: o.Explanation, Resolved: o.Resolved, Needs: o.Needs, Source: o.Source,
		Observer: Module, Run: run, At: at.UTC(), Evidence: []health.Evidence{}}
	if o.Token != "" && o.Token != o.Kind {
		f.Token = o.Token
	}
	said := o.Said
	if said == "" {
		said = o.Summary
	}
	f.Evidence = append(f.Evidence, health.Evidence{At: at.UTC(), Said: said})
	return f
}

// says is what a finding says, its times and the run that wrote it aside: two findings that say the same are one write
// (ADR 0289 §1).
func says(f health.Finding) string {
	f.At, f.Run, f.V = time.Time{}, "", 0
	ev := make([]health.Evidence, len(f.Evidence))
	for i, e := range f.Evidence {
		ev[i] = health.Evidence{Said: e.Said}
	}
	f.Evidence = ev
	raw, _ := json.Marshal(f)
	return string(raw)
}

// worded gives a finding the operator's words registered for its kind, where it says none of its own.
func worded(f Observation) Observation {
	w, ok := words[f.Kind]
	if !ok {
		return f
	}
	if f.Headline == "" {
		f.Headline = w.Headline
	}
	if f.Explanation == "" {
		f.Explanation = w.Explanation
	}
	if f.Resolved == "" {
		f.Resolved = w.Resolved
	}
	if f.Needs == "" {
		f.Needs = w.Needs
	}
	return f
}

type plain struct{ Headline, Explanation, Resolved, Needs string }

// words are the controller's words for each kind the self-check raises (mesh-controller plain_words.go), the
// controller's name for itself replaced by the self-check's where the words spoke of it.
var words = map[string]plain{
	"consumer-lost": {Headline: "A listener on the bus is gone",
		Explanation: "One of the mesh's listeners is no longer on the bus; the next send sets it up again.",
		Resolved:    "The listener is back"},
	"consumer-wrong": {Headline: "A listener on the bus is set up wrong",
		Explanation: "One of the mesh's listeners on the bus is missing or not as defined; the next send sets it up again.",
		Resolved:    "The listener is set up right again"},
	"consumer-behind": {Headline: "Messages pile up for a listener",
		Explanation: "One of the mesh's listeners on the bus is far behind, so what it handles happens late. A healer " +
			"restarts it if it stays.",
		Resolved: "The listener caught up"},
	"stream-wrong": {Headline: "Part of the bus's storage is wrong",
		Needs:       "check the machine the bus runs on; the details say what is missing.",
		Explanation: "A store the mesh keeps on the bus is missing or not as defined, so what it keeps there may be lost.",
		Resolved:    "The bus's storage is right again"},
	"bus-reconnects": {Headline: "A client keeps losing the bus",
		Explanation: "One of the mesh's clients lost its connection to the bus again and again in the last hour. While " +
			"it reconnects, what it says and what it is asked waits.",
		Resolved: "Resolved: the client stays connected"},
	"core-unhealthy": {Headline: "The bus is not healthy",
		Needs: "check the machine the bus runs on; the details say what fails.",
		Explanation: "The bus, which carries every message in the mesh, is not healthy. Instructions, builds and tool " +
			"calls may fail until it recovers.",
		Resolved: "The bus is healthy again"},
	"watchdogs-silent": {Headline: "The mesh's watchdogs stopped",
		Needs: "restart the watchman if this stays, from the mesh MCP server.",
		Explanation: "The watchdogs, which notice when something expected does not happen, do not answer, so missed " +
			"signals are not noticed.",
		Resolved: "The watchdogs run again"},
	"probe-failed": {Headline: "A check of the mesh could not run",
		Explanation: "One of the mesh's own checks could not run, so what it watches is unknown for now. It runs again " +
			"every few minutes.",
		Resolved: "The check runs again"},
}