chore: add instruction for pg-pool plugin (open-telemetry#733)

* chore: add instruction for pg-pool plugin

* chore: update NodeTracer to NodeTracerRegistry

* chore: address comments

Co-authored-by: Valentin Marchaud <thisismac47@gmail.com>
Co-authored-by: Daniel Dyla <dyladan@users.noreply.github.com>

Author: 3 people

packages/opentelemetry-plugin-grpc/README.md

@@ -35,7 +35,7 @@ const registry = new NodeTracerRegistry({
 });
 ```
 
-To load all the [supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
+To load all of the [supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
 ```javascript
 const { NodeTracerRegistry } = require('@opentelemetry/node');
 

packages/opentelemetry-plugin-http/README.md

@@ -36,7 +36,7 @@ const registry = new NodeTracerRegistry({
 });
 ```
 
-To load all the [supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
+To load all of the [supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
 ```js
 const { NodeTracerRegistry } = require('@opentelemetry/node');
 

packages/opentelemetry-plugin-https/README.md

@@ -36,7 +36,7 @@ const registry = new NodeTracerRegistry({
 });
 ```
 
-To load all the [supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
+To load all of the [supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
 ```js
 const { NodeTracerRegistry } = require('@opentelemetry/node');
 

packages/opentelemetry-plugin-ioredis/README.md

@@ -22,9 +22,9 @@ npm install --save @opentelemetry/plugin-ioredis
 
 To load a specific plugin (**ioredis** in this case), specify it in the Node Tracer's configuration
 ```js
-const { NodeTracer } = require('@opentelemetry/node');
+const { NodeTracerRegistry } = require('@opentelemetry/node');
 
-const tracer = new NodeTracer({
+const registry = new NodeTracerRegistry({
   plugins: {
     ioredis: {
       enabled: true,
@@ -35,11 +35,11 @@ const tracer = new NodeTracer({
 });
 ```
 
-To load all the [supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
+To load all of the [supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
 ```javascript
-const { NodeTracer } = require('@opentelemetry/node');
+const { NodeTracerRegistry } = require('@opentelemetry/node');
 
-const tracer = new NodeTracer();
+const registry = new NodeTracerRegistry();
 ```
 
 ## Useful links

packages/opentelemetry-plugin-mongodb/README.md

@@ -36,7 +36,7 @@ const registry = new NodeTracerRegistry({
 });
 ```
 
-To load all the [supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
+To load all of the [supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
 ```js
 const { NodeTracerRegistry } = require('@opentelemetry/node');
 

packages/opentelemetry-plugin-mysql/README.md

@@ -24,9 +24,9 @@ OpenTelemetry MySQL Instrumentation allows the user to automatically collect tra
 
 To load a specific plugin (**MySQL** in this case), specify it in the Node Tracer's configuration
 ```js
-const { NodeTracer } = require('@opentelemetry/node');
+const { NodeTracerRegistry } = require('@opentelemetry/node');
 
-const tracer = new NodeTracer({
+const registry = new NodeTracerRegistry({
   plugins: {
     mysql: {
       enabled: true,
@@ -37,11 +37,11 @@ const tracer = new NodeTracer({
 });
 ```
 
-To load all the [supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
+To load all of the [supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
 ```js
-const { NodeTracer } = require('@opentelemetry/node');
+const { NodeTracerRegistry } = require('@opentelemetry/node');
 
-const tracer = new NodeTracer();
+const registry = new NodeTracerRegistry();
 ```
 
 See [examples/mysql](https://github.com/open-telemetry/opentelemetry-js/tree/master/examples/mysql) for a short example.

packages/opentelemetry-plugin-postgres/opentelemetry-plugin-pg-pool/README.md

@@ -12,20 +12,47 @@ For automatic instrumentation see the
 ## Installation
 
 ```bash
+npm install --save @opentelemetry/plugin-pg
 npm install --save @opentelemetry/plugin-pg-pool
 ```
 
 ## Usage
 
+To load all of the [default supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use the below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
+
 ```js
-const opentelemetry = require('@opentelemetry/plugin-pg-pool');
+const { NodeTracerRegistry } = require('@opentelemetry/node');
 
-// TODO: DEMONSTRATE API
+const registry = new NodeTracerRegistry(); // All default plugins will be used
 ```
 
+If instead you would just want to load a specific plugin (**pg** and **pg-pool** in this case), specify it in the `NodeTracer` configuration. You'll need to install both plugins for full functionality.
+
+```js
+const { NodeTracerRegistry } = require('@opentelemetry/node');
+
+const registry = new NodeTracerRegistry({
+  plugins: {
+    pg: {
+      enabled: true,
+      // You may use a package name or absolute path to the module
+      path: '@opentelemetry/plugin-pg',
+    },
+    'pg-pool': {
+      enabled: true,
+      // You may use a package name or absolute path to the module
+      path: '@opentelemetry/plugin-pg-pool',
+    }
+  }
+});
+```
+
+See [examples/postgres](https://github.com/open-telemetry/opentelemetry-js/tree/master/examples/postgres) for a short example.
+
 ## Supported Versions
 
-- [pg](https://npmjs.com/package/pg-pool): `2.x`
+- [pg](https://npmjs.com/package/pg): `7.x`
+- [pg-pool](https://npmjs.com/package/pg-pool): `2.x` 
 
 ## Useful links
 - For more information on OpenTelemetry, visit: <https://opentelemetry.io/>

packages/opentelemetry-plugin-postgres/opentelemetry-plugin-pg/README.md

@@ -18,20 +18,20 @@ npm install --save @opentelemetry/plugin-pg-pool
 
 ## Usage
 
-To load all of the [default supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use the below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no  computational overhead for listing plugsin for unused modules.
+To load all of the [default supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use the below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
 
 ```js
-const { NodeTracer } = require('@opentelemetry/node');
+const { NodeTracerRegistry } = require('@opentelemetry/node');
 
-const tracer = new NodeTracer(); // All default plugins will be used
+const registry = new NodeTracerRegistry(); // All default plugins will be used
 ```
 
-If instead you would just load a specific plugin (**pg** in this case), specify it in the `NodeTracer` configuration.
+If instead you would just want to load a specific plugin (**pg** in this case), specify it in the `NodeTracer` configuration.
 
 ```js
-const { NodeTracer } = require('@opentelemetry/node');
+const { NodeTracerRegistry } = require('@opentelemetry/node');
 
-const tracer = new NodeTracer({
+const registry = new NodeTracerRegistry({
   plugins: {
     pg: {
       enabled: true,
@@ -45,9 +45,9 @@ const tracer = new NodeTracer({
 If you are using any of the [`pg.Pool`](https://node-postgres.com/api/pool) APIs, you will also need to include the [`pg-pool` plugin](../opentelemetry-plugin-pg-pool).
 
 ```js
-const { NodeTracer } = require('@opentelemetry/node');
+const { NodeTracerRegistry } = require('@opentelemetry/node');
 
-const tracer = new NodeTracer({
+const registry = new NodeTracerRegistry({
   plugins: {
     pg: {
       enabled: true,

packages/opentelemetry-plugin-redis/README.md

@@ -37,7 +37,7 @@ const registry = new NodeTracerRegistry({
 });
 ```
 
-To load all the [supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
+To load all of the [supported plugins](https://github.com/open-telemetry/opentelemetry-js#plugins), use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
 ```javascript
 const { NodeTracerRegistry } = require('@opentelemetry/node');