docs(instrumentation-ioredis): add request hook example

plugins/node/opentelemetry-instrumentation-ioredis/README.md

@@ -2,7 +2,7 @@
 
 [![NPM Published Version][npm-img]][npm-url]
 [![dependencies][dependencies-image]][dependencies-url]
-[![devDependencies][devDependencies-image]][devDependencies-url]
+[![devDependencies][devdependencies-image]][devdependencies-url]
 [![Apache License][license-image]][license-image]
 
 This module provides automatic instrumentation for [`ioredis`](https://github.com/luin/ioredis).
@@ -25,9 +25,11 @@ npm install --save @opentelemetry/instrumentation-ioredis
 To load a specific instrumentation (**ioredis** in this case), specify it in the registerInstrumentations's configuration
 
 ```javascript
-const { NodeTracerProvider } = require('@opentelemetry/node');
-const { IORedisInstrumentation } = require('@opentelemetry/instrumentation-ioredis');
-const { registerInstrumentations } = require('@opentelemetry/instrumentation');
+const { NodeTracerProvider } = require("@opentelemetry/node");
+const {
+  IORedisInstrumentation,
+} = require("@opentelemetry/instrumentation-ioredis");
+const { registerInstrumentations } = require("@opentelemetry/instrumentation");
 
 const provider = new NodeTracerProvider();
 provider.register();
@@ -36,22 +38,22 @@ registerInstrumentations({
   instrumentations: [
     new IORedisInstrumentation({
       // see under for available configuration
-    })
+    }),
   ],
   tracerProvider: provider,
-})
+});
 ```
 
 ### IORedis Instrumentation Options
 
 IORedis instrumentation has few options available to choose from. You can set the following:
 
-| Options | Type | Description |
-| ------- | ---- | ----------- |
-| `dbStatementSerializer` | `DbStatementSerializer` | IORedis instrumentation will serialize db.statement using the specified function. |
-| `requestHook` | `RedisRequestCustomAttributeFunction` (function) | Function for adding custom attributes on db request. Receives params: `span, { moduleVersion, cmdName, cmdArgs }` |
-| `responseHook` | `RedisResponseCustomAttributeFunction` (function) | Function for adding custom attributes on db response |
-| `requireParentSpan` | `boolean` | Require parent to create ioredis span, default when unset is true |
+| Options                 | Type                                              | Description                                                                                                       |
+| ----------------------- | ------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------- |
+| `dbStatementSerializer` | `DbStatementSerializer`                           | IORedis instrumentation will serialize db.statement using the specified function.                                 |
+| `requestHook`           | `RedisRequestCustomAttributeFunction` (function)  | Function for adding custom attributes on db request. Receives params: `span, { moduleVersion, cmdName, cmdArgs }` |
+| `responseHook`          | `RedisResponseCustomAttributeFunction` (function) | Function for adding custom attributes on db response                                                              |
+| `requireParentSpan`     | `boolean`                                         | Require parent to create ioredis span, default when unset is true                                                 |
 
 #### Custom db.statement Serializer
 The instrumentation serializes the whole command into a Span attribute called `db.statement`. The standard serialization format is `{cmdName} {cmdArgs.join(',')}`.
@@ -60,12 +62,33 @@ It is also possible to define a custom serialization function. The function will
 Here is a simple example to serialize the command name skipping arguments:
 
 ```javascript
-const { IORedisInstrumentation } = require('@opentelemetry/instrumentation-ioredis');
+const {
+  IORedisInstrumentation,
+} = require("@opentelemetry/instrumentation-ioredis");
 
 const ioredisInstrumentation = new IORedisInstrumentation({
   dbStatementSerializer: function (cmdName, cmdArgs) {
     return cmdName;
-  }
+  },
+});
+```
+
+#### Using `requestHook`
+
+Instrumentation user can configure a custom "hook" function which will be called on every request with the relevant span and request information. User can then set custom attributes on the span or run any instrumentation extension logic per request.
+
+Here is a simple example that adds and attribute of `ioredis` instrumented version:
+
+```javascript
+const { IORedisInstrumentation } = require('@opentelemetry/instrumentation-ioredis');
+
+const ioredisInstrumentation = new IORedisInstrumentation({
+  requestHook: function(
+            span: Span,
+            requestInfo: IoRedisRequestHookInformation
+          ) {
+    span.setAttribute('instrumented_library.version', requestInfo.moduleVersion)
+  })
 });
 
 ```
@@ -86,6 +109,6 @@ Apache 2.0 - See [LICENSE][license-url] for more information.
 [dependencies-image]: https://status.david-dm.org/gh/open-telemetry/opentelemetry-js-contrib.svg?path=plugins%2Fnode%2Fopentelemetry-instrumentation-ioredis
 [dependencies-url]: https://david-dm.org/open-telemetry/opentelemetry-js-contrib?path=plugins%2Fnode%2Fopentelemetry-instrumentation-ioredis
 [devdependencies-image]: https://status.david-dm.org/gh/open-telemetry/opentelemetry-js-contrib.svg?path=plugins%2Fnode%2Fopentelemetry-instrumentation-ioredis&type=dev
-[devDependencies-url]: https://david-dm.org/open-telemetry/opentelemetry-js-contrib?path=plugins%2Fnode%2Fopentelemetry-instrumentation-ioredis&type=dev
+[devdependencies-url]: https://david-dm.org/open-telemetry/opentelemetry-js-contrib?path=plugins%2Fnode%2Fopentelemetry-instrumentation-ioredis&type=dev
 [npm-url]: https://www.npmjs.com/package/@opentelemetry/instrumentation-ioredis
 [npm-img]: https://badge.fury.io/js/%40opentelemetry%2Finstrumentation-ioredis.svg