Added overview of Prometheus

content/prometheus_overview.adoc

@@ -0,0 +1,11 @@
+[[prometheus_overview]]
+= Prometheus Overview
+////
+First draft
+////
+
+Prometheus is an open-source, microservice monitoring system designed for reliability. This toolkit collects metrics from applications and makes them viewable. DevOps teams can use Prometheus to view application statistics and configure alerts. The toolkit's built-in query language gives DevOps the power to view the data they need to see.
+
+Prometheus servers pull data from targets at a regular frequency and save it for a set period. The application applies rules to collected data to create time-based series or generate alerts. Prometheus users can aggregate time series data and view it in tabular or graph form.
+
+Prometheus is a standalone server application with minimal infrastructure requirements. It is independent from remote services to increase reliability. If infrastructure problems arise, DevOps teams can still rely on Prometheus for diagnostics.

content/querying_istio_metrics.adoc

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+[[querying-istio-metrics-with-prometheus]]
+= Querying Istio Metrics With Prometheus
+
+////
+Pulled from istio.github.io and converted from Markdown to Asciidoc
+////
+
+This process illustrates how to query Istio metrics with Prometheus from the web interface.
+
+The link:/istio-docs/Doc-Installing-ServiceMesh/topics/tutorial-bookinfo.adoc/[Bookinfo] application is used in the examples presented here.
+
+[[before-you-begin]]
+== Before You Begin
+
+link:/docs/setup/[Install Istio] in your cluster and deploy an
+application.
+
+[[querying-istio-metrics]]
+== Querying Istio Metrics
+
+1.  Verify that the `prometheus` service is running in your cluster.
++
+In Kubernetes environments, issue the following command:
++
+----
+kubectl -n istio-system get svc prometheus NAME
+CLUSTER-IP EXTERNAL-IP PORT(S) AGE prometheus 10.59.241.54 9090/TCP 2m
+----
++
+2.  Send traffic to the mesh.
++
+For the Bookinfo sample, visit `http://$GATEWAY_URL/productpage` in your
+web browser or issue the following command:
++
+----
+curl http://$GATEWAY_URL/productpage
+----
++
+[NOTE]
+====
+`$GATEWAY_URL` is the value set in the
+link:/istio-docs/Doc-Installing-ServiceMesh/topics/tutorial-bookinfo.adoc/[Bookinfo] example.
+====
+
+3.  Start the Prometheus web interface.
++
+In Kubernetes environments, issue this command:
++
+----
+kubectl -n istio-system port-forward $(kubectl -n
+istio-system get pod -l app=prometheus -o
+jsonpath=`\{.items[0].metadata.name}') 9090:9090 &
+----
++
+4. Visit http://localhost:9090/graph in your web browser.
+
+5.  Run a Prometheus query.
++
+In the `Expression` input box at the top of the web page, enter the
+text: `istio_requests_total` and click *Execute*.
++
+The result will resemble this:
++
+----
+< image width=``100%'' ratio=``42.63%''
+link=``./prometheus_query_result.png'' caption=``Prometheus Query
+Result'' >
+----
+
+[[additional-queries]]
+=== Additional Queries
+
+* Total count of all requests to the `productpage` service:
++
+----
+istio_requests_total\{destination_service=``productpage.default.svc.cluster.local''}
+----
+
+* Total count of all requests to `v3` of the `reviews` service:
++
+----
+istio_requests_total\{destination_service=``reviews.default.svc.cluster.local'',
+destination_version=``v3''}
+----
+
+* Rate of requests over the past 5 minutes to all instances of the
+`productpage` service:
++
+----
+rate(istio_requests_total\{destination_service=~“productpage.*``,
+response_code=''200“}[5m])
+----
+
+[[about-the-prometheus-add-on]]
+== About the Prometheus Add-On
+
+Mixer includes a built-in https://prometheus.io[Prometheus] adapter
+that exposes an endpoint serving generated metric values. The Prometheus
+add-on is a Prometheus server preconfigured to scrape Mixer
+endpoints to collect the exposed metrics. It provides a mechanism for
+persistent storage and querying of Istio metrics.
+
+The configured Prometheus add-on scrapes three endpoints:
+
+1.  *istio-mesh* (`istio-mixer.istio-system:42422`): all Mixer-generated
+mesh metrics.
+2.  *mixer* (`istio-mixer.istio-system:9093`): all Mixer-specific
+metrics for monitoring the Mixer.
+3.  *envoy* (`istio-mixer.istio-system:9102`): raw stats generated by
+Envoy translated from Statsd to Prometheus.
+
+For more on querying Prometheus, see
+https://prometheus.io/docs/querying/basics/[the Prometheus query documentation].
+
+[[cleanup]]
+== Cleanup
+
+1. Remove any `kubectl port-forward` processes that are still running:
++
+----
+killall kubectl
+----
+
+2. When you are finished, see the
+link:/istio-docs/Doc-Installing-ServiceMesh/topics/tutorial-bookinfo.adoc/[Removing the Bookinfo Application] instructions to
+remove the application.