jschoubben
c4030947b0
0056 is 'the authority is the control plane, not a database'. A citation pointing at the wrong decision is worse than none: it reads as corroboration. Claude-Session: https://claude.ai/code/session_01LrgweAeERJYBg88c5cKDzF
95 lines
3.4 KiB
Go
95 lines
3.4 KiB
Go
package catalogue
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import (
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"fmt"
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"regexp"
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"sort"
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"strings"
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)
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// What a module may say about the machine it is running on.
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//
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// **A module cannot know where it will be assigned, and sometimes it must say so anyway.** Every
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// other name in a declaration is either the module's own — which it wrote — or something it
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// requires, which arrives as a binding. The machine underneath is neither: it is chosen when the
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// module is assigned, long after the manifest was written, and until now nothing carried it into a
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// file.
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//
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// The case that found this is a certificate authority inside the mesh (novox/hq ADR 0066). A proxy
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// reaches it at the address the mesh handed over, `<machine>.internal` — so the authority's own
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// certificate has to be issued for that name, or the first thing that happens is the proxy refusing
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// to talk to it. The authority is the one thing that cannot be told its name by a binding: it
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// provides, it does not require. Written as a literal it would be a manifest carrying one
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// deployment's machine name, which is the shape [ADR 0066] exists to remove.
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//
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// Two facts, both the mesh's own vocabulary — the same `node` and `at` a contribution already
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// carries. Nothing about what a machine is *for*: that would be the mesh learning what a module
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// means, which it does not do.
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// ofMachine is where a module says a fact about the machine underneath it belongs:
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// ${machine:<key>}.
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var ofMachine = regexp.MustCompile(`\$\{machine:([a-z0-9][a-z0-9_-]*)\}`)
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// machineUsed are the keys a file's content asks for, first appearance first.
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func machineUsed(content string) []string {
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var used []string
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seen := map[string]bool{}
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for _, m := range ofMachine.FindAllStringSubmatch(content, -1) {
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if key := m[1]; !seen[key] {
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seen[key] = true
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used = append(used, key)
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}
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}
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return used
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}
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// machineFacts is what a module may name about the machine it was assigned to.
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//
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// `at` is absent rather than empty when the machine is not on the private network. A module asking
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// to be reached at an address that does not exist is a misconfiguration, and it is said here —
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// where the module and the machine are both named — rather than discovered later as a certificate
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// nobody can verify.
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func machineFacts(r Resolution) map[string]string {
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out := map[string]string{"name": r.Node}
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if r.At != "" {
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out["at"] = r.At
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}
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return out
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}
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// machineInto replaces a file's ${machine:…} placeholders with what the mesh knows about the
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// machine the module was assigned to.
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//
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// A key the mesh does not hold is refused, for the same reason a binding's is: left alone, the
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// literal would be written into a configuration file and read as a value.
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func machineInto(resource map[string]any, facts map[string]string, module string) error {
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if fmt.Sprint(resource["type"]) != "file" {
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return nil
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}
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content, ok := resource["content"].(string)
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if !ok {
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return nil
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}
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for _, key := range machineUsed(content) {
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value, has := facts[key]
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if !has {
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return fmt.Errorf(
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"%s has a file that says ${machine:%s}, and this machine says %s",
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module, key, orNothing(namesOfFacts(facts)))
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}
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resource["content"] = strings.ReplaceAll(
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content, fmt.Sprintf("${machine:%s}", key), value)
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content = resource["content"].(string)
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}
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return nil
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}
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func namesOfFacts(facts map[string]string) []string {
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out := make([]string, 0, len(facts))
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for k := range facts {
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out = append(out, k)
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}
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sort.Strings(out)
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return out
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}
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