| 1 | // App-internal instance visibility: apps MAY expose GET /.carlos/instances |
| 2 | // on their public host (the contract is INSTANCES.md, next to this file) and |
| 3 | // the console renders what they report. The fetch is deliberately meek — a |
| 4 | // short timeout, a small size cap, a brief cache — because an app that is |
| 5 | // slow, asleep, or silent must cost the app page nothing but this section. |
| 6 | package console |
| 7 | |
| 8 | import ( |
| 9 | "context" |
| 10 | "encoding/json" |
| 11 | "io" |
| 12 | "net/http" |
| 13 | "strings" |
| 14 | "sync" |
| 15 | "time" |
| 16 | ) |
| 17 | |
| 18 | const ( |
| 19 | // InstancesPath is the well-known path of the instance-report contract. |
| 20 | InstancesPath = "/.carlos/instances" |
| 21 | // instancesTimeout bounds one report fetch: past it the app is simply |
| 22 | // "not reporting" — the page never hangs on a slow tenant. |
| 23 | instancesTimeout = 1500 * time.Millisecond |
| 24 | // instancesTTL is how long a fetched report (or a failure) is reused |
| 25 | // before the host is asked again. |
| 26 | instancesTTL = 30 * time.Second |
| 27 | // instancesMaxBody caps the response body read; bigger is "not reporting". |
| 28 | instancesMaxBody = 64 << 10 |
| 29 | // instancesMaxCount caps how many instances one report may list. |
| 30 | instancesMaxCount = 100 |
| 31 | ) |
| 32 | |
| 33 | // Instance is one row of an app's self-report. Slug is required; everything |
| 34 | // else is optional color. Unknown JSON fields are ignored. |
| 35 | type Instance struct { |
| 36 | Slug string `json:"slug"` |
| 37 | Status string `json:"status"` |
| 38 | Region string `json:"region"` |
| 39 | Detail string `json:"detail"` |
| 40 | } |
| 41 | |
| 42 | // InstanceReport is what the app page renders: which host was asked and what |
| 43 | // it said. Reporting is false when the host was polled but didn't answer the |
| 44 | // contract (no endpoint, an error, a timeout, junk) — the page then renders |
| 45 | // exactly as it did before this feature existed. |
| 46 | type InstanceReport struct { |
| 47 | Host string |
| 48 | Instances []Instance |
| 49 | Reporting bool |
| 50 | } |
| 51 | |
| 52 | // instanceFetcher polls apps for their reports through their public hosts, |
| 53 | // caching per host so page reloads don't drum on tenants. |
| 54 | type instanceFetcher struct { |
| 55 | client *http.Client |
| 56 | scheme string |
| 57 | timeout time.Duration |
| 58 | |
| 59 | mu sync.Mutex |
| 60 | cache map[string]instanceCacheEntry |
| 61 | } |
| 62 | |
| 63 | type instanceCacheEntry struct { |
| 64 | report InstanceReport |
| 65 | fetched time.Time |
| 66 | } |
| 67 | |
| 68 | func newInstanceFetcher(client *http.Client, scheme string) *instanceFetcher { |
| 69 | if client == nil { |
| 70 | client = &http.Client{Timeout: instancesTimeout} |
| 71 | } |
| 72 | if scheme == "" { |
| 73 | scheme = "https" |
| 74 | } |
| 75 | return &instanceFetcher{ |
| 76 | client: client, |
| 77 | scheme: scheme, |
| 78 | timeout: instancesTimeout, |
| 79 | cache: map[string]instanceCacheEntry{}, |
| 80 | } |
| 81 | } |
| 82 | |
| 83 | // Report picks the app's reporting host and fetches (or reuses) its report. |
| 84 | // The host is the first ready, non-static, non-sidecar route that has NOT |
| 85 | // opted into hibernation — polling a hibernatable host could wake it, and |
| 86 | // the console must never wake an app just to draw a table. A sidecar route |
| 87 | // is excluded for a different reason: its Host is a derived |
| 88 | // .sidecar.internal label nothing can dial (design §4.1), so choosing it |
| 89 | // would make a HEALTHY app read "not reporting" purely because the picker |
| 90 | // landed on an unroutable row from the same app's route set (Assemble groups |
| 91 | // by app NAME with no kind filter). nil means no route is pollable, which |
| 92 | // renders the same as "not reporting". |
| 93 | func (f *instanceFetcher) Report(ctx context.Context, routes []RouteView) *InstanceReport { |
| 94 | for _, rt := range routes { |
| 95 | if rt.Host == "" || rt.Kind == "static" || rt.Kind == "sidecar" || rt.Status != "ready" || rt.Hibernate { |
| 96 | continue |
| 97 | } |
| 98 | rep := f.get(ctx, rt.Host) |
| 99 | return &rep |
| 100 | } |
| 101 | return nil |
| 102 | } |
| 103 | |
| 104 | func (f *instanceFetcher) get(ctx context.Context, host string) InstanceReport { |
| 105 | now := time.Now() |
| 106 | f.mu.Lock() |
| 107 | if e, ok := f.cache[host]; ok && now.Sub(e.fetched) < instancesTTL { |
| 108 | f.mu.Unlock() |
| 109 | return e.report |
| 110 | } |
| 111 | f.mu.Unlock() |
| 112 | rep := f.fetch(ctx, host) |
| 113 | f.mu.Lock() |
| 114 | f.cache[host] = instanceCacheEntry{report: rep, fetched: now} |
| 115 | f.mu.Unlock() |
| 116 | return rep |
| 117 | } |
| 118 | |
| 119 | // fetch asks one host once. Every failure mode — connect error, non-200, |
| 120 | // oversized body, invalid JSON — folds to Reporting=false; the contract is |
| 121 | // opt-in and silence is a fine answer. |
| 122 | func (f *instanceFetcher) fetch(ctx context.Context, host string) InstanceReport { |
| 123 | rep := InstanceReport{Host: host} |
| 124 | ctx, cancel := context.WithTimeout(ctx, f.timeout) |
| 125 | defer cancel() |
| 126 | req, err := http.NewRequestWithContext(ctx, http.MethodGet, f.scheme+"://"+host+InstancesPath, nil) |
| 127 | if err != nil { |
| 128 | return rep |
| 129 | } |
| 130 | res, err := f.client.Do(req) |
| 131 | if err != nil { |
| 132 | return rep |
| 133 | } |
| 134 | defer res.Body.Close() |
| 135 | if res.StatusCode != http.StatusOK { |
| 136 | return rep |
| 137 | } |
| 138 | body, err := io.ReadAll(io.LimitReader(res.Body, instancesMaxBody+1)) |
| 139 | if err != nil || len(body) > instancesMaxBody { |
| 140 | return rep |
| 141 | } |
| 142 | var raw []Instance |
| 143 | if err := json.Unmarshal(body, &raw); err != nil { |
| 144 | return rep |
| 145 | } |
| 146 | var out []Instance |
| 147 | for _, in := range raw { |
| 148 | if strings.TrimSpace(in.Slug) == "" { |
| 149 | continue // slug is the one required field; slugless rows are noise |
| 150 | } |
| 151 | out = append(out, in) |
| 152 | if len(out) == instancesMaxCount { |
| 153 | break |
| 154 | } |
| 155 | } |
| 156 | rep.Instances, rep.Reporting = out, true |
| 157 | return rep |
| 158 | } |
| 159 | |
amadan