npm package: @rozek/sds-sidecar-jj
Description: sidecar daemon for shareable-data-store (json-joy CRDT backend)
Author: Andreas Rozek
Latest version: 0.0.13

# @rozek/sds-sidecar-jj

A long-running daemon that keeps a local copy of one SDS (Shareable Data Store) in sync with a WebSocket relay server and fires configured HTTP webhooks whenever the store changes. Uses the **json-joy** CRDT backend.

Built on top of `@rozek/sds-sidecar`.

---

## Prerequisites

- **Node.js** 22.5 or later
- a running **SDS WebSocket relay server** (e.g. `@rozek/sds-websocket-server`) reachable at a `ws://` or `wss://` URL
- a valid **JWT** signed with the relay server's secret, with at minimum `read` scope and an `aud` claim matching the target store ID
- all clients connected to the same relay — including this sidecar — must use the **same CRDT backend** (`@rozek/sds-core-jj`). Patch and snapshot bytes are backend-specific binary formats; mixing backends in one deployment will cause silent data corruption or deserialization errors

---

## Installation

```bash
npm install -g @rozek/sds-sidecar-jj
```

Or use without installation via npx:

```bash
npx @rozek/sds-sidecar-jj <ws-url> <store-id> [options]
```

---

## Synopsis

```
sds-sidecar-jj <ws-url> <store-id> [options]
```

Both positional arguments may also be supplied through environment variables or a JSON config file (see below); the command-line values always take precedence.

---

## Options

### Identity

| Option | Description |
| --- | --- |
| `--token <jwt>` | JWT for the WebSocket server (env: `SDS_TOKEN`) |
| `--config <file>` | path to a JSON config file |

### Persistence

| Option | Description |
| --- | --- |
| `--persistence-dir <path>` | directory for the local SQLite database (env: `SDS_PERSISTENCE_DIR`, default: `~/.sds`) |

### Inline webhook

| Option | Description |
| --- | --- |
| `--webhook-url <url>` | webhook endpoint URL |
| `--webhook-token <token>` | bearer token sent with all outgoing webhook calls (env: `SDS_WEBHOOK_TOKEN`) |
| `--topic <string>` | opaque string echoed in the `Topic` field of every payload from this webhook |
| `--watch <uuid>` | restrict notifications to entries physically nested inside this subtree (identified by UUID) |
| `--depth <n>` | maximum watch depth (default: unlimited) |
| `--on <trigger>` | trigger condition — repeatable; at least one required when `--webhook-url` is set |

> **Note:** `--watch` uses the UUID of the subtree root. Only entries that are physically nested inside that subtree are observed. Entries that are merely linked to from within the subtree are **not** automatically included. If the UUID does not exist in the store at the time a change occurs, the webhook is silently suppressed for that change.

### Auth-error webhook

| Option | Description |
| --- | --- |
| `--on-auth-error <url>` | webhook URL to notify when the server rejects the token (uses `--webhook-token` too) |

### Logging

| Option | Description |
| --- | --- |
| `--verbose` | log incoming patches and store changes (env: `SDS_VERBOSE=1`) |

### Reconnect tuning

| Option | Default | Description |
| --- | --- | --- |
| `--reconnect-initial <ms>` | 1000 | initial reconnect delay in milliseconds |
| `--reconnect-max <ms>` | 60000 | maximum reconnect delay in milliseconds |
| `--reconnect-jitter <f>` | 0.1 | jitter fraction 0–1 applied to each delay |

---

## Environment Variables

| Variable | Description |
| --- | --- |
| `SDS_SERVER_URL` | WebSocket base URL — must start with `ws://` or `wss://` (overridden by positional `<ws-url>`) |
| `SDS_STORE_ID` | store identifier (overridden by positional `<store-id>`) |
| `SDS_TOKEN` | JWT for the WebSocket server |
| `SDS_WEBHOOK_TOKEN` | bearer token for all outgoing webhook HTTP calls |
| `SDS_PERSISTENCE_DIR` | directory for the local SQLite database |
| `SDS_ON_AUTH_ERROR` | webhook URL to notify when the server rejects the token |
| `SDS_VERBOSE` | set to `1` to log incoming patches and store changes |

---

## JSON Config File

When `--config <file>` is given, options are read from a JSON file. CLI options and environment variables take precedence over file values.

```json
{
  "ServerURL":     "wss://relay.example.com",
  "StoreId":       "my-store",
  "Token":         "<jwt>",
  "PersistenceDir": "/var/lib/sds",
  "WebHookToken":  "<bearer-token>",
  "onAuthError":   "https://admin.example.com/auth-error",
  "Verbose":       true,

  "reconnect": {
    "initialDelay": 1000,
    "maxDelay":     60000,
    "Jitter":       0.1
  },

  "WebHooks": [
    {
      "URL":      "https://hooks.example.com/store-changed",
      "Topic":    "my-topic",
      "Watch":    "<entry-uuid>",   // UUID of the subtree root; link targets not included
      "maxDepth": 2,
      "on":       [ "create", "delete", "value:application/json" ]
    }
  ]
}
```

---

## Trigger Syntax

Each `--on` value (or `"on"` array element in the config file) is one of:

| Trigger | Fires when… |
| --- | --- |
| `change` | any watched entry changes in any way |
| `create` | a watched entry is moved into a non-trash container |
| `delete` | a watched entry is moved to the trash or purged |
| `value` | the value of a watched item changes |
| `value:<mime-glob>` | the value changes and the item's MIME type matches the glob (e.g. `value:image/*`) |
| `info:<key>=<value>` | the `Info.<key>` field of a watched entry changes to the given value |

MIME globs support `*` (any sequence) and `?` (any single character). Matching is case-insensitive. Only the first `=` in an `info:` trigger is the separator, so values may contain `=`.

---

## Webhook Payload

Every matching webhook receives an HTTP POST with a JSON body. Each request times out after **10 seconds**; a non-2xx response is logged to stderr but does not stop the sidecar.

```json
{
  "StoreId":        "my-store",
  "Trigger":        "value:image/*",
  "Topic":          "my-topic",
  "changedEntries": ["<uuid-1>", "<uuid-2>"],
  "Timestamp":      "2026-01-15T10:30:00.000Z"
}
```

`Topic` is only present when `--topic` (or `"Topic"` in the config file) is set. The `Authorization: Bearer <token>` header is included when a webhook token is set.

---

## Reconnect Behaviour

When the WebSocket connection drops for any reason other than an auth error, the sidecar reconnects automatically using exponential backoff:

- initial delay: `--reconnect-initial` ms (default 1 s)
- doubles each attempt: 1 s → 2 s → 4 s → … → cap
- hard cap: `--reconnect-max` ms (default 60 s)
- ±`--reconnect-jitter` fraction added randomly to each delay (default 10 %)

---

## Auth Errors

When the server closes the WebSocket connection with code **4001** (Unauthorized — JWT rejected) or **4003** (Forbidden — JWT valid but does not match the store's audience), the sidecar:

1. Logs the error to stderr with a clear message
2. Fires the `--on-auth-error` webhook (if configured), with a JSON body:

```json
{
  "StoreId":   "my-store",
  "ServerURL": "wss://relay.example.com",
  "Code":      4001,
  "Reason":    "Unauthorized"
}
```

`Code` is either `4001` (JWT rejected) or `4003` (JWT valid but store audience mismatch). `Reason` is the close-frame reason string, or the label `"Unauthorized"` / `"Forbidden"` when the server sends none.

3. Exits without attempting to reconnect

The bearer token sent with the auth-error webhook is the same `--webhook-token` / `SDS_WEBHOOK_TOKEN` used for all other webhooks — it is entirely separate from the SDS JWT (`--token` / `SDS_TOKEN`).

---

## Exit Codes

| Code | Name | Meaning |
| --- | --- | --- |
| 0 | OK | clean shutdown (SIGINT / SIGTERM) |
| 1 | GeneralError | unspecified runtime error |
| 2 | UsageError | bad arguments or missing required option |
| 3 | NotFound | config file not found |
| 4 | Unauthorized | server rejected the JWT (WS close code 4001) |
| 5 | NetworkError | reserved (not currently used at exit) |
| 6 | Forbidden | JWT valid but store access denied (WS close code 4003) |

---

## Examples

**Minimal — inline webhook for any change:**

```bash
sds-sidecar-jj wss://relay.example.com my-store \
  --token "$SDS_TOKEN" \
  --webhook-url https://hooks.example.com/changed \
  --on change
```

**Watch a subtree at depth 1 for new JSON items, with a routing topic:**

```bash
sds-sidecar-jj wss://relay.example.com my-store \
  --token "$SDS_TOKEN" \
  --webhook-url https://hooks.example.com/new-doc \
  --topic new-document \
  --watch "<subtree-root-uuid>" \
  --depth 1 \
  --on "value:application/json"
```

**Notify an admin endpoint on auth failure:**

```bash
sds-sidecar-jj wss://relay.example.com my-store \
  --token "$SDS_TOKEN" \
  --on-auth-error https://admin.example.com/token-expired \
  --webhook-token "$HOOK_TOKEN" \
  --on change
```

**Using a config file for multiple webhooks:**

```bash
sds-sidecar-jj --config /etc/sds/my-store.json
```

**Via npx without a global install:**

```bash
npx @rozek/sds-sidecar-jj wss://relay.example.com my-store \
  --token "$SDS_TOKEN" \
  --on change
```

---

## License

[MIT License](../../LICENSE.md) © Andreas Rozek