Clarify what it means to filter metrics from processors

dekumar23 · Oct 30, 2017 · 777b84d · 777b84d
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diff --git a/docs/AGGREGATORS_AND_PROCESSORS.md b/docs/AGGREGATORS_AND_PROCESSORS.md
@@ -39,6 +39,11 @@ metrics as they pass through Telegraf:
 
 Both Aggregators and Processors analyze metrics as they pass through Telegraf.
 
+Use [measurement filtering](CONFIGURATION.md#measurement-filtering)
+to control which metrics are passed through a processor or aggregator.  If a
+metric is filtered out the metric bypasses the plugin and is passed downstream
+to the next plugin.
+
 **Processor** plugins process metrics as they pass through and immediately emit
 results based on the values they process. For example, this could be printing
 all metrics or adding a tag to all metrics that pass through.

diff --git a/docs/CONFIGURATION.md b/docs/CONFIGURATION.md
@@ -98,9 +98,13 @@ you can configure that here.
 * **name_suffix**: Specifies a suffix to attach to the measurement name.
 * **tags**: A map of tags to apply to a specific input's measurements.
 
+The [measurement filtering](#measurement-filtering) parameters can be used to
+limit what metrics are emitted from the input plugin.
+
 ## Output Configuration
 
-There are no generic configuration options available for all outputs.
+The [measurement filtering](#measurement-filtering) parameters can be used to
+limit what metrics are emitted from the output plugin.
 
 ## Aggregator Configuration
 
@@ -121,13 +125,21 @@ aggregator and will not get sent to the output plugins.
 * **name_suffix**: Specifies a suffix to attach to the measurement name.
 * **tags**: A map of tags to apply to a specific input's measurements.
 
+The [measurement filtering](#measurement-filtering) parameters be used to
+limit what metrics are handled by the aggregator.  Excluded metrics are passed
+downstream to the next aggregator.
+
 ## Processor Configuration
 
 The following config parameters are available for all processors:
 
 * **order**: This is the order in which the processor(s) get executed. If this
 is not specified then processor execution order will be random.
 
+The [measurement filtering](#measurement-filtering) can parameters may be used
+to limit what metrics are handled by the processor.  Excluded metrics are
+passed downstream to the next processor.
+
 #### Measurement Filtering
 
 Filters can be configured per input, output, processor, or aggregator,
@@ -377,3 +389,15 @@ to the system load metrics due to the `namepass` parameter.
 [[outputs.file]]
   files = ["stdout"]
 ```
+
+#### Processor Configuration Examples:
+
+Print only the metrics with `cpu` as the measurement name, all metrics are
+passed to the output:
+```toml
+[[processors.printer]]
+  namepass = "cpu"
+
+[[outputs.file]]
+  files = ["/tmp/metrics.out"]
+```