loki.process: document limitation of stage.json (#6082)

* loki.process: document limitation of stage.json Signed-off-by: Paschalis Tsilias <[email protected]> * Add example error for future grepping Signed-off-by: Paschalis Tsilias <[email protected]> * Apply Clayton's suggestions Signed-off-by: Paschalis Tsilias <[email protected]> --------- Signed-off-by: Paschalis Tsilias <[email protected]> Co-authored-by: Clayton Cornell <[email protected]>
grafana · Jan 10, 2024 · ee98c5f · ee98c5f
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diff --git a/docs/sources/flow/reference/components/loki.process.md b/docs/sources/flow/reference/components/loki.process.md
@@ -382,6 +382,20 @@ following key-value pair to the set of extracted data.
 username: agent
 ```
 
+{{% admonition type="note" %}}
+Due to a limitation of the upstream jmespath library, you must wrap any string
+that contains a hyphen `-` in quotes so that it's not considered a numerical
+expression.
+
+If you don't use quotes to wrap a string that contains a hyphen, you will get
+errors like: `Unexpected token at the end of the expression: tNumber`
+
+You can use one of two options to circumvent this issue:
+
+1. An escaped double quote. For example: `http_user_agent = "\"request_User-Agent\""`
+1. A backtick quote. For example: ``http_user_agent = `"request_User-Agent"` ``
+{{% /admonition %}}
+
 ### stage.label_drop block
 
 The `stage.label_drop` inner block configures a processing stage that drops labels