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Persist the Galaxy browse dataset to disk for offline startup

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The gateway can lose connectivity to the Galaxy database, and the
database is often unreachable exactly when the gateway restarts. The
hierarchy cache was purely in-memory, so a cold start with no database
left clients with an Unavailable browse surface until SQL came back.

Add a JSON snapshot store: each successful heavy refresh writes the raw
hierarchy and attribute rowsets to disk atomically (temp file + rename),
and the first refresh after startup restores that snapshot before any
SQL runs. Restored data is served as Stale until a live query confirms
it; a live query that observes the same time_of_last_deploy promotes it
to Healthy with no heavy re-query.

Persistence is on by default (MxGateway:Galaxy:PersistSnapshot) and
writes to C:\ProgramData\MxGateway\galaxy-snapshot.json.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Joseph Doherty
2026-05-22 02:03:00 -04:00
parent aba228f443
commit fa491c752b
11 changed files with 739 additions and 32 deletions
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docs/GatewayConfiguration.md
+5 -1
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@@ -60,7 +60,9 @@ paths, timeouts, queue sizes, enum values, or protocol values are invalid.
"Galaxy": {
"ConnectionString": "Server=localhost;Database=ZB;Integrated Security=True;TrustServerCertificate=True;Encrypt=False;",
"CommandTimeoutSeconds": 60,
"DashboardRefreshIntervalSeconds": 30
"DashboardRefreshIntervalSeconds": 30,
"PersistSnapshot": true,
"SnapshotCachePath": "C:\\ProgramData\\MxGateway\\galaxy-snapshot.json"
},
"Alarms": {
"Enabled": false,
@@ -170,6 +172,8 @@ at startup.
| `MxGateway:Galaxy:ConnectionString` | `Server=localhost;Database=ZB;Integrated Security=True;TrustServerCertificate=True;Encrypt=False;` | SQL Server connection string for the Galaxy Repository (`ZB`) used by the `GalaxyRepository` browse RPCs. Override in production via `MxGateway__Galaxy__ConnectionString`. |
| `MxGateway:Galaxy:CommandTimeoutSeconds` | `60` | Per-command SQL timeout for all Galaxy browse RPCs. |
| `MxGateway:Galaxy:DashboardRefreshIntervalSeconds` | `30` | Interval between background refreshes of the dashboard Galaxy summary cache. SQL is hit at most once per interval regardless of dashboard render rate. |
| `MxGateway:Galaxy:PersistSnapshot` | `true` | Persists the latest successful Galaxy browse dataset to disk. When `true`, the cache reloads that snapshot at startup so clients can still browse last-known data while the Galaxy database is unreachable. The restored data is served with `Stale` status until a live query confirms it. |
| `MxGateway:Galaxy:SnapshotCachePath` | `C:\ProgramData\MxGateway\galaxy-snapshot.json` | File path for the persisted Galaxy browse snapshot. Ignored when `PersistSnapshot` is `false`. The snapshot is written atomically (temp file plus rename). |
See [Galaxy Repository Browse](./GalaxyRepository.md) for the RPC surface and
behavior.