Document our logging framework and ControlZ. (#2000)

content/help/ops/component-logging/index.md

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-Logging is good.
+Istio components are built with a flexible logging framework which provides a number of features and controls to
+help operate these components and facilitate diagnostics. You control these logging features by passing
+command-line options when starting the components.
+
+## Logging scopes
+
+Logging messages output by a component are categorized by *scopes*. A scope represents a set of related log messages which
+you can control as a whole. Different components have different scopes, depending on the features the component
+provides. All components have the `default` scope, which is used for non-categorized log messages.
+
+As an example, as of this writing, Mixer has 5 scopes, representing different functional areas within Mixer:
+
+- `adapters`
+- `api`
+- `attributes`
+- `default`
+- `grpcAdapter`
+
+Pilot, Citadel, and Galley have their own scopes which you can discover by looking at their [reference documentation](/docs/reference/commands/).
+
+Each scope has a unique output level which is one of:
+
+1. none
+1. error
+1. warning
+1. info
+1. debug
+
+where `none` produces no output for the scope, and `debug` produces the maximum amount of output. The default level for all scopes
+is `info` which is intended to provide the right amount of logging information for operating Istio in normal conditions.
+
+To control the output level, you use the `--log_output_level` command-line option. For example:
+
+{{< text bash >}}
+$ mixs server --log_output_level attributes=debug,adapters=warning
+{{< /text >}}
+
+In addition to controlling the output level from the command-line, you can also control the output level of a running component
+by using its [ControlZ](/help/ops/controlz) interface.
+
+## Controlling output
+
+Log messages are normally sent to a component's standard output stream. The `--log_target` option lets you direct the output to
+any number of different locations. You give the option a comma-separated list of file system paths, along with the special
+values `stdout` and `stderr` to indicate the standard output and standard error streams respectively.
+
+Log messages are normally output in a human-friendly format. The `--log_as_json` option can be used to force the output into JSON,
+which can be easier for tools to process.
+
+## Log rotation
+
+Istio components can automatically manage log rotation, which make it simple to break up large logs into smaller log files.
+The `--log_rotate` option lets you specify the base file name to use for rotation. Derived names will be used for individual
+log files.
+
+The `--log_rotate_max_age` option lets you specify the maximum number of days before file rotation takes place, while the `--log_rotate_max_size` option
+let you specify the maximum size in megabytes before file rotation takes place. Finally, the `--log_rotate_max_backups` option lets you control
+the maximum number of rotated files to keep, older files will be automatically deleted.
+
+## Component debugging
+
+The `--log_caller` and `--log_stacktrace_level` options let you control whether log information includes
+programmer-level information. This is useful when trying to track down bugs in a component but is not
+normally used in day-to-day operation.

content/help/ops/controlz/index.md

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 keywords: [ops]
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-ControlZ is good.
+Istio components are built with a flexible introspection framework which makes it easy to inspect and manipulate the internal state
+of a running component. Components open a port which can be used from a web browser to get an interactive view into the state of the
+component, or via REST for access and control from external tools.
+
+Mixer, Pilot, and Galley all implement the ControlZ functionality. When these components start, a message is logged indicating the
+IP address and port to connect to in order to interact with ControlZ.
+
+{{< text plain >}}
+2018-07-26T23:28:48.889370Z     info    ControlZ available at 100.76.122.230:9876
+{{< /text >}}
+
+Here's sample of the ControlZ interface:
+
+{{< image width="80%" ratio="47.52%"
+    link="./ctrlz.png"
+    caption="ControlZ User Interface"
+    >}}
+
+The `--ctrlz_port` and `--ctrlz_address` command-line options can be given when starting a component to control the
+specific address and port where ControlZ should be exposed.