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W2.7 (format): an event kept last per subject, in a stream of its own

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The node-engine's running.<node>.<module> is kept last per subject with no age limit, which the shared events stream cannot say; the reader takes keep last-per-subject.

Claude-Session: https://claude.ai/code/session_01JG73KEq4zoDfM9WtYpcQgZ
This commit is contained in:
jschoubben
2026-11-09 20:39:43 +01:00
parent 3034867fb6
commit 7d04e0df29
2 changed files with 25 additions and 0 deletions
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go/seatdef/seatdef.go
+19
View File
@@ -122,8 +122,19 @@ type Message struct {
// still knows the event. Empty, the subject is the name. A part `<node>` is the node that publishes it, which
// the grants part grants a node's account alone (ADR 0363 §2).
Subject string `json:"subject,omitempty"`
// Keep says how an event is kept when not as the family keeps the seat's others: KeepLastPerSubject, in a stream
// of its own named KeptStream, the last message of each subject and no age limit (design 47: the node-engine's
// running.<node>.<module>, so the last build of every module on every node stays on the bus however long ago
// it was said, and a durable consumer starting from the last message per subject holds them all).
Keep string `json:"keep,omitempty"`
}
// KeepLastPerSubject is an event kept last per subject with no age limit, in a stream of its own.
const KeepLastPerSubject = "last-per-subject"
// KeptStream is the stream an event with Keep is kept in: `<seat>.<event>`, as a family is `<seat>.events`.
func KeptStream(seat string, m Message) string { return seat + "." + m.Name }
// SubjectPattern is the event's subject after the seat's event prefix with its parts between angle brackets: the
// name itself when the definition gives no subject.
func (m Message) SubjectPattern() string {
@@ -663,6 +674,14 @@ func checkMessages(field string, ms []Message, whole bool) Problems {
ps = append(ps, Problem{where + ".name", fmt.Sprintf("%q twice", m.Name)})
}
seen[m.Name] = true
switch {
case m.Keep != "" && field != "events":
ps = append(ps, Problem{where + ".keep", "only an event is kept"})
case m.Keep != "" && m.Keep != KeepLastPerSubject:
ps = append(ps, Problem{where + ".keep", fmt.Sprintf("%q is not %s", m.Keep, KeepLastPerSubject)})
case m.Keep != "" && len(m.Parts()) == 0 && !m.ByCaller:
ps = append(ps, Problem{where + ".keep", "an event of one subject kept last per subject is one message: give it a subject with parts"})
}
if m.Subject != "" && field != "events" {
ps = append(ps, Problem{where + ".subject", "only an event carries a subject of its own"})
} else if why := checkSubject(m); why != "" {
go/seatdef/seatdef_test.go
+6
View File
@@ -63,6 +63,12 @@ func TestADefinitionIsReadStrictlyNamingWhatIsWrong(t *testing.T) {
`"name":"running","subject":"running.<node>.<node>"`, 1), "part <node> twice"},
{"a subject on an event named by its caller", strings.Replace(whole, `"name":"created"`,
`"name":"owed","by-caller":true,"subject":"owed.<number>"`, 1), "carries no subject of its own"},
{"an event kept last per subject", strings.Replace(whole, `"name":"created"`,
`"name":"running","subject":"running.<node>.<module>","keep":"last-per-subject"`, 1), ""},
{"an event kept otherwise", strings.Replace(whole, `"name":"created"`,
`"name":"running","subject":"running.<node>","keep":"forever"`, 1), `events[0].keep: "forever" is not last-per-subject`},
{"an event of one subject kept last per subject", strings.Replace(whole, `"name":"created"`,
`"name":"running","keep":"last-per-subject"`, 1), "give it a subject with parts"},
{"an accept with dotted words", strings.Replace(whole, `"events":`,
`"accepts":[{"name":"run.now","body":{}}],"events":`, 1), "accepts[0].name"},
{"a verb twice", strings.Replace(listGrain, `]}`, `,{"name":"add"}]}`, 1), `"add" twice`},