add quoteservice docs (#392)

Author: Juliano Costa

docs/service_table.md

@@ -14,6 +14,6 @@ View [Service Graph](../README.md#architecture) to visualize request flows.
 | [loadgenerator](../src/loadgenerator/README.md)                 | Python/Locust   | Continuously sends requests imitating realistic user shopping flows to the frontend.                                                         |
 | [paymentservice](../src/paymentservice/README.md)               | JavaScript      | Charges the given credit card info (mock) with the given amount and returns a transaction ID.                                                |
 | [productcatalogservice](../src/productcatalogservice/README.md) | Go              | Provides the list of products from a JSON file and ability to search products and get individual products.                                   |
-| [quoteservice](../src/quoteservice/README.md)                   | PHP             | Calculates the shipping costs, based on the number of items to be shipped.                                                                   |
+| [quoteservice](services/quoteservice.md)                   | PHP             | Calculates the shipping costs, based on the number of items to be shipped.                                                                   |
 | [recommendationservice](../src/recommendationservice/README.md) | Python          | Recommends other products based on what's given in the cart.                                                                                 |
 | [shippingservice](../src/shippingservice/README.md)             | Rust            | Gives shipping cost estimates based on the shopping cart. Ships items to the given address (mock).                                           |

docs/services/quoteservice.md

@@ -0,0 +1,112 @@
+# quote service
+
+This service is responsible for calculating shipping costs, based on
+the number of items to be shipped. The quote service is called from
+Shipping Service via HTTP.
+
+The Quote Service is implemented using the Slim framework and
+php-di for managing the Dependency Injection.
+
+The PHP instrumentation may vary when using a different framework.
+
+[Quote service source](../../src/quoteservice/)
+
+## Traces
+
+### Initialize tracer provider
+
+The OpenTelemetry SDK is initialized from `index`.
+
+```php
+    $tracerProvider = (new TracerProviderFactory('quoteservice'))->create();
+    ShutdownHandler::register([$tracerProvider, 'shutdown']);
+    $tracer = $tracerProvider->getTracer('io.opentelemetry.contrib.php');
+
+    $containerBuilder->addDefinitions([
+        Tracer::class => $tracer
+    ]);
+```
+
+You should call `$tracerProvider->shutdown()` when your service is shutdown to
+ensure all spans are exported.
+
+### Adding HTTP instrumentation
+
+This service receives HTTP requests, which are instrumented in the middleware.
+
+The middleware starts root span based on route pattern, sets span status
+from http code.
+
+```php
+    $app->add(function (Request $request, RequestHandler $handler) use ($tracer) {
+        $parent = TraceContextPropagator::getInstance()->extract($request->getHeaders());
+        $routeContext = RouteContext::fromRequest($request);
+        $route = $routeContext->getRoute();
+        $root = $tracer->spanBuilder($route->getPattern())
+            ->setStartTimestamp((int) ($request->getServerParams()['REQUEST_TIME_FLOAT'] * 1e9))
+            ->setParent($parent)
+            ->setSpanKind(SpanKind::KIND_SERVER)
+            ->startSpan();
+        $scope = $root->activate();
+
+        try {
+            $response = $handler->handle($request);
+            $root->setStatus($response->getStatusCode() < 500 ? StatusCode::STATUS_OK : StatusCode::STATUS_ERROR);
+        } finally {
+            $root->end();
+            $scope->detach();
+        }
+
+        return $response;
+    });
+```
+
+This is enough to get a new span every time a new request is received by the service.
+
+Note that the `root` span is created with `setParent($parent)` which is coming from
+the request headers. This is required to ensure Context Propagation.
+
+### Add span attributes
+
+Within the definition of routes, you can get current span using
+`OpenTelemetry\API\Trace\AbstractSpan`.
+
+```php
+    $span = AbstractSpan::getCurrent();
+```
+
+Adding attributes to a span is accomplished using `setAttribute` on the span
+object. In the `calculateQuote` function 2 attributes are added to the `childSpan`.
+
+```php
+    $childSpan->setAttribute('app.quote.items.count', $numberOfItems);
+    $childSpan->setAttribute('app.quote.cost.total', $quote);
+```
+
+### Add span events
+
+Adding span events is accomplished using `addEvent` on the span object. In the
+`getquote` route span events are added. Some events have
+additional attributes, others do not.
+
+Adding a span event without attributes:
+
+```php
+    $span->addEvent('Received get quote request, processing it');
+```
+
+Adding a span event with additional attributes:
+
+```php
+    $span->addEvent('Quote processed, response sent back', [
+        'app.quote.cost.total' => $payload
+    ]);
+```
+
+## Metrics
+
+TBD
+
+## Logs
+
+TBD

src/quoteservice/app/routes.php

@@ -46,7 +46,9 @@ function calculateQuote($jsonObject, Tracer $tracer): float
         $payload = json_encode($data);
         $response->getBody()->write($payload);
 
-        $span->addEvent('Quote processed, response sent back');
+        $span->addEvent('Quote processed, response sent back', [
+            'app.quote.cost.total' => $data
+        ]);
 
         return $response
             ->withHeader('Content-Type', 'application/json');