adding file source page (#11355) (#11486)

Author: opensearch-trigger-bot[bot]

_data-prepper/pipelines/configuration/sources/file.md

@@ -0,0 +1,92 @@
+---
+layout: default
+title: File
+parent: Sources
+grand_parent: Pipelines
+nav_order: 24
+---
+
+# File source
+
+The `file` plugin reads events from a local file once when the pipeline starts. It's useful for loading seed data, testing processors and sinks, or replaying a fixed dataset. This source *does not monitor* the file for new lines after startup.
+
+Option | Required | Type | Description
+:--- | :--- | :--- | :---
+`path` | Yes | String | An absolute path to the input file inside the Data Prepper container, for example, `/usr/share/data-prepper/data/input.jsonl`.
+`format` | No | String | Specifies how to interpret the file content. Valid values are `json` and `plain`. Use `json` when your file has one JSON object per line or a JSON array. Use `plain` for raw text lines. Default is `plain`.
+`record_type` | No | String | The type of output record produced by the source. Valid values are `event` and `string`. Use `event` to produce structured events expected by downstream processors and the OpenSearch sink. Default is `string`.
+
+### Example
+
+The following examples demonstrate how different file types can be processed.
+
+### JSON file
+
+The following example processes a JSON file:
+
+```yaml
+file-to-opensearch:
+  source:
+    file:
+      path: /usr/share/data-prepper/data/input.ndjson
+      format: json
+      record_type: event
+  sink:
+    - opensearch:
+        hosts: ["https://opensearch:9200"]
+        index: file-demo
+        username: admin
+        password: admin_pass
+        insecure: true
+```
+{% include copy.html %}
+
+### Plain text file
+
+A raw text file can be processed using the following pipeline:
+
+```yaml
+plain-file-to-opensearch:
+  source:
+    file:
+      path: /usr/share/data-prepper/data/app.log
+      format: plain
+      record_type: event
+  processor:
+    - grok:
+        match:
+          message:
+            - '%{TIMESTAMP_ISO8601:timestamp} \[%{LOGLEVEL:level}\] %{GREEDYDATA:msg}'
+  sink:
+    - opensearch:
+        hosts: ["https://opensearch:9200"]
+        index: plain-file-demo
+        username: admin
+        password: admin_pass
+        insecure: true
+```
+{% include copy.html %}
+
+### CSV file
+
+You can process a CSV file using the `csv` processor:
+
+```yaml
+csv-file-to-opensearch:
+  source:
+    file:
+      path: /usr/share/data-prepper/data/ingest.csv
+      format: plain  
+      record_type: event     
+  processor:
+    - csv:
+        column_names: ["time","level","message"]
+  sink:
+    - opensearch:
+        hosts: ["https://opensearch:9200"]
+        index: csv-demo
+        username: admin
+        password: admin_pass
+        insecure: true
+```
+{% include copy.html %}