Merge pull request #1245 from tpmccallum/observability

Add observability (OTEL)

content/spin/v2/dynamic-configuration.md

@@ -5,6 +5,7 @@ date = "2023-11-04T00:00:01Z"
 url = "https://github.com/fermyon/developer/blob/main/content/spin/v2/dynamic-configuration.md"
 
 ---
+
 - [Application Variables Runtime Configuration](#application-variables-runtime-configuration)
   - [Environment Variable Provider](#environment-variable-provider)
   - [Vault Application Variable Provider](#vault-application-variable-provider)
@@ -15,7 +16,7 @@ url = "https://github.com/fermyon/developer/blob/main/content/spin/v2/dynamic-co
 - [SQLite Storage Runtime Configuration](#sqlite-storage-runtime-configuration)
   - [LibSQL Storage Provider](#libsql-storage-provider)
 - [LLM Runtime Configuration](#llm-runtime-configuration)
-- [Remote Compute Provider](#remote-compute-provider)
+  - [Remote Compute Provider](#remote-compute-provider)
 
 Configuration for Spin application features such as [application variables](./variables),
 [key value storage](./kv-store-api-guide), [SQL storage](./sqlite-api-guide)
@@ -25,13 +26,6 @@ requiring no changes to the application code itself.
 This runtime configuration data is stored in the `runtime-config.toml` file and passed in via the `--runtime-config-file` flag
 when invoking the `spin up` command.
 
-The list of Spin features supporting runtime configuration includes:
-
-- [Application Variables](#variables-runtime-configuration)
-- [Key Value Storage](#key-value-store-runtime-configuration)
-- [SQL storage](#sqlite-storage-runtime-configuration)
-- [Serverless AI Compute](#llm-runtime-configuration)
-
 Let's look at each configuration category in-depth below.
 
 ## Application Variables Runtime Configuration

content/spin/v2/observing-apps.md

@@ -0,0 +1,39 @@
+title = "Observing Applications"
+template = "spin_main"
+date = "2023-11-04T00:00:01Z"
+enable_shortcodes = true
+[extra]
+url = "https://github.com/fermyon/developer/blob/main/content/spin/v2/observing-apps.md"
+
+---
+
+- [Logs](#logs)
+- [OpenTelemetry (OTEL)](#opentelemetry-otel)
+
+## Logs
+
+Spin handles application logs by default, storing output and error messages from file system-run applications in the `.spin/logs` directory alongside the manifest file's location. Users have the option to direct logs to a specific folder using the `--log-dir` flag of the `spin up` command. Additionally, if users wish to prevent `stdout` and `stderr` from being written to disk, they can specify an empty string for the `--log-dir` flag, i.e. `spin up --log-dir ""` - effectively disabling log storage. See the [persistent logs](./running-apps#persistent-logs) section for more details.
+
+## OpenTelemetry (OTEL)
+
+Spin now has experimental support for the [OpenTelemetry (OTEL)](https://opentelemetry.io/) observability standard. When configured, Spin will now emit traces of your Spin App as an OTEL [signal](https://opentelemetry.io/docs/concepts/signals/). Here is a brief overview of how to configure it.
+
+First, run an OTEL compliant [collector](https://opentelemetry.io/docs/collector/) to collect the traces. [Jaeger](https://www.jaegertracing.io/) is an open source distributed tracing platform that can act as an OTEL collector and enables viewing taces. You can run Jaeger using Docker:
+
+```bash
+docker run -d -p16686:16686 -p4317:4317 -p4318:4318 -e COLLECTOR_OTLP_ENABLED=true jaegertracing/all-in-one:latest
+```
+
+Now, you can start your Spin app, setting the endpoint of the OTEL collector in the **`OTEL_EXPORTER_OTLP_ENDPOINT`** environment variable:
+
+```bash
+OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4318 spin up
+```
+
+After sending some requests to your Spin app, navigate to Jaeger `http://localhost:16686` to view the traces.
+
+![Traces from app](/static/image/jaeger-traces.png)
+
+Spin supports both inbound and outbound [trace context propagation](https://opentelemetry.io/docs/concepts/context-propagation/). This allows you to include Spin in your distributed traces that span all your services.
+
+This observability support in Spin is still experimental. Only the HTTP trigger, the LLM host component, and outbound HTTP requests are implemented at this time. Going forward, we will be adding tracing to the remainder of Spin triggers and host components. We also hope to add support for the OTEL metrics signal in the future. Try it out, let us know what you think and help us improve the observability experience in Spin!

templates/spin_sidebar_v2.hbs

@@ -47,6 +47,11 @@
                                         href="{{site.info.base_url}}/spin/v2/distributing-apps">Publishing and
                                         Distribution</a>
                         </li>
+                        <li><a {{#if (active_project request.spin-full-url "/spin/v2/observing-apps" )}}
+                                        class="active" {{/if}}
+                                        href="{{site.info.base_url}}/spin/v2/observing-apps">Observing
+                                        Applications</a>
+                        </li>
                         <li><a {{#if (active_project request.spin-full-url "/spin/v2/troubleshooting-application-dev"
                                         )}} class="active" {{/if}}
                                         href="{{site.info.base_url}}/spin/v2/troubleshooting-application-dev">Troubleshooting