markap14 commented on a change in pull request #3725: NIFI-6558 Added
Parameters to User Guide and Sys Admin Guide
URL: https://github.com/apache/nifi/pull/3725#discussion_r323901654
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File path: nifi-docs/src/main/asciidoc/user-guide.adoc
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@@ -711,15 +711,187 @@ whatever comments are appropriate for this component.
Use of the Comments tab is
image::comments-tab.png["Comments Tab"]
-=== Additional Help
+==== Additional Help
You can access additional documentation about each Processor's usage by
right-clicking on the Processor and selecting 'Usage' from the context menu.
Alternatively, select Help from the Global Menu in the top-right corner of the
UI to display a Help page with all of the documentation, including usage
documentation for all the Processors that are available. Click on the desired
Processor to view usage documentation.
+[[Parameters]]
+=== Parameters
+The values of properties in the flow, including sensitive properties, can be
parameterized using Parameters. Parameters are created and configured within
the NiFi UI. Any property can be configured to reference a Parameter with the
following conditions:
+
+ - A sensitive property can only reference a Sensitive Parameter
+ - A non-sensitive property can only reference a non-Sensitive Parameter
+ - Properties that reference Controller Services can not use Parameters
+
+NOTE: NiFi automatically picks up new or modified parameters.
+
+[[parameter-contexts]]
+==== Parameter Contexts
+Parameters are created within Parameter Contexts. Parameter Contexts are
globally defined/accessible to the NiFi instance. Access policies can be
applied to Parameter Contexts to determine which users can create them. Once
created, policies to read and write to a specific Parameter Context can also be
applied (see <<accessing-parameters>> for more information).
+
+===== Creating a Parameter Context
+To create a Parameter Context, select Parameter Contexts from the Global Menu:
+
+image:parameter-contexts-selection.png["Global Menu - Parameter Contexts"]
+
+In the Parameter Contexts window, click the `+` button in the upper-right
corner and the Add Parameter Context window opens. The window has two tabs:
Settings and Parameters.
+
+image:parameter-contexts-settings.png["Parameter Contexts - Settings"]
+
+On the "Settings" tab, add a name for the Parameter Context and a description
if desired. Select "Apply" to save the Parameter Context or select the
"Parameters" tab to add parameters to the context.
+
+==== Adding a Parameter to a Parameter Context
+Parameters can be added during Parameter Context creation or added to existing
Parameter Contexts.
+
+During Parameter Context creation, select the "Parameters" tab. Click the `+`
button to open the Add Parameter window.
+
+image:add-parameter-during-parameter-context-creation.png[Add Parameter]
+
+To add parameters to an existing Parameter Context, open the Parameter Context
window and click the Edit button (image:iconEdit.png["Edit"]) in the row of the
desired Parameter Context.
+
+image:edit-parameter-context.png[Edit Parameter Context]
+
+On the "Parameters" tab, click the `+` button to open the Add Parameter window.
+
+The Add Parameter window has the following settings:
+
+- *Name* - A name that is used to denote the Parameter. Only alpha-numeric
characters (a-z, A-Z, 0-9), hyphens ( - ), underscores ( _ ), periods ( . ),
and spaces are allowed.
+
+- *Value* - The value that will be used when the Parameter is referenced.
+
+- *Set empty string* - Check to explicity set the value of the Parameter to an
empty string. Unchecked by default.
+
+- *Sensitive Value* - Set to "Yes" if the Parameter's Value should be
considered sensitive. If sensitive, the value of the Parameter will not be
shown in the UI once applied. The default setting is "No".
+
+- *Description* - A description that explains what the Parameter is, how it is
to be used, etc. This field is optional.
+
+Once these settings are configured, select "Apply". Add additional Parameters
or edit any existing Parameters.
+
+image:update-parameter-context.png[Update Parameter Context]
+
+To complete the process, select "Apply" from the Parameter Context window. The
following operations are performed to validate all components that reference
the added or modified parameters: Stopping/Restarting affected Processors,
Disabling/Re-enabling affected Controller Services, Updating Parameter Context.
+
+image:parameters-validate-affected-components.png[Validate Affected Components]
+
+The Referencing Components section lists any components referencing the
parameters in the parameter context organized by process group.
+
+[[assigning_parameter_context_to_PG]]
+==== Assigning a Parameter Context to a Process Group
+For a component to reference a Parameter, its Process Group must first be
assigned to a Parameter Context. Once assigned, processors and controller
services within that Process Group may only reference Parameters within that
Parameter Context.
+
+NOTE: A user can only set the Parameter Context of a Process Group to one of
the Parameter Contexts that the user has the view policy for. Additionally, in
order to set the Parameter Context, the user must have the modify policy for
the Process Group. See <<accessing-parameters>> for more information.
+
+To assign a Parameter Context to a Process group, click Configure, either from
the Operate Palette or from the Process Group context menu.
+
+image:process-group-configuration-parameters.png[Configure Process Group
Parameter Context]
+
+In the Flow Configuration window, select the "General" tab. From the Process
Group Parameter Context drop-down menu, select an existing Parameter Context or
create a new one.
+
+image:process-group-parameter-context-menu.png[Process Group Parameter Context
Menu]
+
+Select "Apply" to save the configuration changes. The Process Group context
menu now includes a "Parameters" option which allows quick access to the Update
Parameter Context window for the assigned Parameter Context.
+
+image:context-menu-parameters-option.png[Context Menu Parameters Option]
+
+If the Parameter Context for a Process Group is changed, all components that
reference any Parameters in that Process Group will be stopped, validated, and
restarted (assuming the changes are valid).
+
+NOTE: If a Parameter Context is unset from a Process Group, it does *NOT*
inherit the Parameter Context from the parent Process Group. Instead, no
Parameters can be referenced. Any component that does already reference a
Parameter will become invalid.
+
+==== Referencing Parameters
+
+===== Parameter Reference Syntax
+To configure an eligible property to reference a Parameter, use the `#` symbol
as the start, with the Parameter's name enclosed in curly braces:
+
+`#{Parameter.Name}`
+
+This can be escaped using an additional `#` character at the beginning. To
illustrate this, assume that the Parameter `abc` has a value of `xxx` and
Parameter `def` has a value of `yyy`. Then, the following user-defined property
values will evaluate to these effective values:
+
+|================================================================================================================================================================
+| *User-Entered Literal Property Value* | *Effective Property Value*
| *Explanation*
+| `#{abc}` | `xxx`
| Simple substitution
+| `+#{abc}/data+` | `xxx/data`
| Simple substitution with additional literal data
+| `+#{abc}/#{def}+` | `xxx/yyy`
| Multiple substitution with additional literal data
+| `+#{abc+` | `+#{abc+`
| No { } for parameter replacement
+| `+#abc+` | `+#abc+`
| No { } for parameter replacement
+| `+##{abc}+` | `+#{abc}+`
| Escaped # for literal interpretation
+| `+###{abc}+` | `#xxx`
| Escaped # for literal interpretation, followed by simple substitution
+| `+####{abc}+` | `+##{abc}+`
| Escaped # for literal interpretation, twice
+| `+#####{abc}+` | `+##xxx+`
| Escaped # for literal interpretation, twice, followed by simple
substitution
+| `+#{abc/data}+` | Exception thrown on property set
operation | `/` not a valid parameter name character
+|================================================================================================================================================================
+
+When referencing a Parameter from within
link:expression-language-guide.html[Expression Language], the Parameter
reference is evaluated first. As an example, to replace `xxx` with `zzz` for
the `abc` Parameter:
Review comment:
I believe this is inaccurate. I think it was like this when the initial
commit landed but was changed to make things easier to understand. If you use
the below EL, it will evaluate to the literal value "#{abc}". If you wanted to
actually reference the parameter, then change the xxx to zzz you'd just use `${
#{abc}:replace('xxx', 'zzz') }`
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