doc: add doc how to send logs to syslog server in vector

doc/source/admin/monitoring.rst

@@ -166,6 +166,57 @@ Prometheus as the data source.  You can find more examples of how to do
 this in the Grafana Helm chart `Import Dashboards <https://github.com/grafana/helm-charts/tree/main/charts/grafana#import-dashboards>`_
 documentation.
 
+Send logs to syslog server
+==========================
+
+It is possilbe to send logs to a syslog server which has the reception
+enabled via socket. You will need to simply set the following inventory
+variables for vector.
+
+.. code-block:: yaml
+
+  vector_helm_values:
+    customConfig:
+      transforms:
+        syslog_logs:
+          type: remap
+          inputs: ["kubernetes_logs"]
+          # let's make RFC 5424 compatible messages for rsyslog
+          # read more about the format:
+          # https://blog.datalust.co/seq-input-syslog/#rfc5424
+          source: |-
+            pri = 1 * 8 + to_syslog_severity(.severity) ?? 6
+
+            ., err = join([
+              "<" + to_string(pri) + ">" + "1",     # <pri>version
+              to_string!(.@timestamp),
+              to_string!(.kubernetes.pod_name || .hostname || "${VECTOR_SELF_NODE_NAME}"),
+              to_string!(.app || .kubernetes.labels.app || "-"),
+              "-",                                  # procid
+              to_string!(.messageid || "-"),        # msgid
+              "-",                                  # structured-data
+              decode_base16!("EFBBBF") + to_string!(.message || encode_json(.))   # msg
+            ], separator: " ")
+
+            if err != null {
+              log("Unable to construct syslog message for event:" + err + ". Dropping invalid event: " + encode_json(.), level: "error", rate_limit_secs: 10)
+            }
+      sinks:
+        rsyslog_general:
+          type: "socket"
+          inputs: [syslog_logs]
+          # rsyslog server address
+          address: "38.108.68.134:514"
+          # tcp or udp
+          mode: "tcp"
+          encoding:
+            codec: "text"
+          framing:
+            method: "newline_delimited"
+
+This configures a vector transformer converting log messages to rsyslog
+format and sends logs to the specified rsyslog server.
+
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