feat(server): implement switchable logging formats (console/json) (#24791)

* feat(server): add LogFormat enum and configuration

* feat(server): add structured logging formatters

* feat(server): implement switchable logging formats (console/json)

* Revert "feat(server): add LogFormat enum and configuration"

This reverts commit 565e95ae68.

* feat(server): implement JSON logging using NestJS native support

* refactor: rename LOG_FORMAT to IMMICH_LOG_FORMAT for consistency

* docs: add IMMICH_LOG_FORMAT documentation

* chore: format environment-variables.md

* chore: format monitoring.md

docs/docs/features/monitoring.md

@@ -112,4 +112,40 @@ You can then make a new panel, specifying Prometheus as the data source for it.
 
 -- TODO: add images and more details here
 
+## Structured Logging
+
+In addition to Prometheus metrics, Immich supports structured JSON logging which is ideal for log aggregation systems like Grafana Loki, ELK Stack, Datadog, Splunk, and others.
+
+### Configuration
+
+By default, Immich outputs human-readable console logs. To enable JSON logging, set the `IMMICH_LOG_FORMAT` environment variable:
+
+```bash
+IMMICH_LOG_FORMAT=json
+```
+
+:::tip
+The default is `IMMICH_LOG_FORMAT=console` for human-readable logs with colors during development. For production deployments using log aggregation, use `IMMICH_LOG_FORMAT=json`.
+:::
+
+### JSON Log Format
+
+When enabled, logs are output in structured JSON format:
+
+```json
+{"level":"log","pid":36,"timestamp":1766533331507,"message":"Initialized websocket server","context":"WebsocketRepository"}
+{"level":"warn","pid":48,"timestamp":1766533331629,"message":"Unable to open /build/www/index.html, skipping SSR.","context":"ApiService"}
+{"level":"error","pid":36,"timestamp":1766533331690,"message":"Failed to load plugin immich-core:","context":"Error"}
+```
+
+This format includes:
+
+- `level`: Log level (log, warn, error, etc.)
+- `pid`: Process ID
+- `timestamp`: Unix timestamp in milliseconds
+- `message`: Log message
+- `context`: Service or component that generated the log
+
+For more information on log formats, see [`IMMICH_LOG_FORMAT`](/install/environment-variables.md#general).
+
 [prom-file]: https://github.com/immich-app/immich/releases/latest/download/prometheus.yml

docs/docs/install/environment-variables.md

@@ -34,6 +34,7 @@ These environment variables are used by the `docker-compose.yml` file and do **N
 | `TZ`                                | Timezone                                                                                  |        <sup>\*1</sup>        | server                   | microservices      |
 | `IMMICH_ENV`                        | Environment (production, development)                                                     |         `production`         | server, machine learning | api, microservices |
 | `IMMICH_LOG_LEVEL`                  | Log level (verbose, debug, log, warn, error)                                              |            `log`             | server, machine learning | api, microservices |
+| `IMMICH_LOG_FORMAT`                 | Log output format (`console`, `json`)                                                     |          `console`           | server                   | api, microservices |
 | `IMMICH_MEDIA_LOCATION`             | Media location inside the container ⚠️**You probably shouldn't set this**<sup>\*2</sup>⚠️ |           `/data`            | server                   | api, microservices |
 | `IMMICH_CONFIG_FILE`                | Path to config file                                                                       |                              | server                   | api, microservices |
 | `NO_COLOR`                          | Set to `true` to disable color-coded log output                                           |           `false`            | server, machine learning |                    |