out_influxdb: documentation for tag prefix stripping

pipeline/outputs/influxdb.md

@@ -22,6 +22,7 @@
 | `org` | InfluxDB organization name where the bucket is (v2 only). | `fluent` |
 | `port` | TCP port of the target InfluxDB service. | `8086` |
 | `sequence_tag` | The name of the tag whose value is incremented for consecutive simultaneous events. | _none_ |
+| `strip_prefix` | String prefix to be removed from the front of `tag` when writing InfluxDB measurement names. `strip_prefix` is removed only if it matches exactly at the beginning of and is strictly shorter than `tag` (`tag` length will not be reduced to zero if `strip_prefix` and `tag` are identical strings). | _none_ |
 | `tag_keys` | Space-separated list of keys to tag. | _none_ |
 | `uri` | Custom URI endpoint. | _none_ |
 | `workers` | The number of [workers](../../administration/multithreading.md#outputs) to perform flush operations for this output. | `0` |
@@ -143,6 +144,85 @@
 `Auto_Tags=On` in this example causes an error, because every parsed field value type is `string`. The best usage of this option in metrics like record where one or more field value isn't `string` typed.
 
 
+### Prefix stripping
+
+When collecting data from many inputs into many buckets, it can be helpful to remove a common prefix using `Strip_prefix`.
+
+{% tabs %}
+{% tab title="fluent-bit.yaml" %}
+
+```yaml
+pipeline:
+  inputs:
+    - name: cpu
+      tag: cpu.one
+    - name: cpu
+      tag: cpu.two
+    - name: cpu
+      tag: gpu.one
+    - name: cpu
+      tag: gpu.two
+
+
+  outputs:
+    - name: influxdb
+      match: 'cpu*'
+      host: 127.0.0.1
+      port: 8086
+      bucket: cpubucket
+      strip_prefix: cpu.
+    - name: influxdb
+      match: 'gpu*'
+      host: 127.0.0.1
+      port: 8086
+      bucket: gpubucket
+      strip_prefix: gpu.
+```
+
+{% endtab %}
+{% tab title="fluent-bit.conf" %}
+
+```text
+[INPUT]
+    Name  cpu
+    Tag   cpu.one
+
+[INPUT]
+    Name  cpu
+    Tag   cpu.two
+
+[INPUT]
+    Name  cpu
+    Tag   gpu.one
+
+[INPUT]
+    Name  cpu
+    Tag   gpu.two
+
+[OUTPUT]
+    Name          influxdb
+    Host          127.0.0.1
+    Port          8086
+    Match         cpu*
+    Bucket        cpubucket
+    Strip_prefix  cpu.
+
+[OUTPUT]
+    Name          influxdb
+    Host          127.0.0.1
+    Port          8086
+    Match         gpu*
+    Bucket        gpubucket
+    Strip_prefix  gpu.
+```
+
+{% endtab %}
+{% endtabs %}
+
+
+This will result in the buckets `cpubucket` and `gpubucket` each containing two measurement streams named `one` and `two`. Without prefix stripping, the measurement names would be `cpu.one` and `cpu.two` (stored in `cpubucket`), and `gpu.one`, `gpu.two` (stored in `gpubucket`).
+
+
 ### Testing
 
 Before starting Fluent Bit, ensure the target database exists on InfluxDB. Using the previous example, insert the data into a `fluentbit` database.