DOC-964 New bloblang error functions

[asimms41]

Description

Resolves DOC-964
Review deadline: 22nd January

Page previews

Bloblang functions

Checks

• New feature
• Content gap
• Support Follow-up
• Small fix (typos, links, copyedits, etc)

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[mihaitodor]

LGTM, thank you!

[JakeSCahill]

Do we need to add these functions with more examples of real outputs to xref:configuration:error_handling.adoc?

[mihaitodor]

@JakeSCahill Good point! I took a stab at it here:

diff --git a/modules/configuration/pages/error_handling.adoc b/modules/configuration/pages/error_handling.adoc
index 73907a5..84e279d 100644
--- a/modules/configuration/pages/error_handling.adoc
+++ b/modules/configuration/pages/error_handling.adoc
@@ -49,18 +49,21 @@ pipeline:
 
 == Logging errors
 
-When an error occurs there will occasionally be useful information stored within the error flag that can be exposed with the interpolation function xref:configuration:interpolation.adoc#bloblang-queries[`error`]. This allows you to expose the information with processors.
+When an error occurs there will occasionally be useful information stored within the error flag that can be exposed with the interpolation function xref:configuration:interpolation.adoc#bloblang-queries[`error`]. Additionally, you can use the xref:guides:bloblang/methods.adoc#error_source_label[`error_source_label`], xref:guides:bloblang/methods.adoc#error_source_name[`error_source_name`] and / or xref:guides:bloblang/methods.adoc#error_source_path[`error_source_path`] bloblang functions to get extra information about the processor which failed.
 
-For example, when catching failed processors you can xref:components:processors/log.adoc[`log`] the messages:
+For example, when xref:components:processors/catch.adoc[`catch`]ing failed processors, you can xref:components:processors/log.adoc[`log`] the error message along with the label of the processor which failed:
 
 [source,yaml]
 ----
 pipeline:
   processors:
-    - resource: foo # Processor that might fail
+    - try:
+      - resource: foo # Processor that might fail
+      - resource: bar # Processor that might fail
+      - resource: baz # Processor that might fail
     - catch:
       - log:
-          message: "Processing failed due to: ${!error()}"
+          message: "Processor ${!error_source_label()} failed due to: ${!error()}"
 ----
 
 Or perhaps augment the message payload with the error message:

You can experiment with this:

res.yaml

processor_resources:
  - label: foo
    mapping: |
      root = content().uppercase()

  - label: bar
    mapping: |
      root = throw("kaboom!")

  - label: baz
    mapping: |
      root = content() + "blobfish"

conf.yaml

pipeline:
  processors:
    - try:
      - resource: foo # Processor that might fail
      - resource: bar # Processor that might fail
      - resource: baz # Processor that might fail

    - catch:
      - log:
          message: "Processor ${!error_source_label()} failed due to: ${!error()}"

$ rpk connect run -r res.yaml conf.yaml

Type something and hit enter.

WDYT? (cc @asimms41)