RFC: add opentelemetry support

text/0000-opentelemetry-metrics.md

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+# Meta
+[meta]: #meta
+- Name: Enable OpenTelemetry Metrics
+- Start Date: 2023-10-09
+- Author(s): qiaoleiatms
+- Status: Draft <!-- Acceptable values: Draft, Approved, On Hold, Superseded -->
+- RFC Pull Request: 
+- CNB Pull Request: 
+- CNB Issue: 
+- Supersedes: N/A
+
+# Summary
+[summary]: #summary
+
+The lifecycle should support to collect metrics about phases and buildpacks.
+
+# Motivation
+[motivation]: #motivation
+
+As a service provider who provides the build functionalities to the end users by leveraging CNB buildpacks, it's not easy to know the service running state in real-time.
+
+To support send metrics will give us a chance to understand how the service is running and how to improve the availability.
+
+# What it is
+[what-it-is]: #what-it-is
+
+
+This RFC proposes to collect metrics over OpenTelemetry (Also known as [OTel](https://opentelemetry.io/docs/what-is-opentelemetry/), an `Observebility` framework for metrics, tracing and logging.)
+  - Metrics of phases
+  - Metrics of buildpacks
+
+And then, send the metrics to the supported [exporters](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/exporter)
+
+
+# How it Works
+[how-it-works]: #how-it-works
+
+- Metrics of phases - For each phase, should define at least below metrics
+  - Count of phase been executed
+  - Success count of phase been executed
+  - Time duration of phase been executed
+- Metrics of buildpacks - For each buildpack participates in build phase, should define at least below metrics
+  - Count of buildpack been executed
+  - Success count of buildpack been executed
+  - Time duration of buildpack been executed
+- By default, the metrics collection could be disabled, unless a flag `CNB_METRICS_ENABLED=true` is given.
+- If metrics collection is enabled, by default, the metrics should send to the console, unless a flag `CNB_METRICS_EXPORTER=xxx` is configured to send metrics to a supported [exporters](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/exporter), and should support the most popular ones in priority:
+  - prometheusexporter
+  - influxdbexporter
+  - kafkaexporter
+  - zipkinexporter
+  - fileexporter
+  - azuredataexplorerexporter
+  - azuremonitorexporter
+  - dynatraceexporter
+  - opencensusexporter
+  - splunkhecexporter
+  - datadogexporter
+- Configuration of different exporters should be able to be defined in file ([example](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/exporter/fileexporter/README.md#example)) and pass to lifecycle during `pack build`
+
+    `pack build --builder {builder_name} -p {path_to_source} --exporter-conf {path_to_conf}`
+
+# Migration
+[migration]: #migration
+
+N/A
+
+# Drawbacks
+[drawbacks]: #drawbacks
+
+If we don't, there's no way for service owner/provider to know the overall status of build.
+
+# Alternatives
+[alternatives]: #alternatives
+
+
+Instead, lifecycle should generate the parsable report of phases and buildpacks, for example:
+
+```json
+{
+    "phases": [
+        {"phase": "analyze", "executed": "true", "succeeded": true, "durationInMs": "3456"},
+        {"phase": "detect", "executed": "true", "succeeded": true, "durationInMs": "3456"},
+        {"phase": "restore", "executed": "true", "succeeded": true, "durationInMs": "3456"},
+        {"phase": "build", "executed": "true", "succeeded": false, "durationInMs": "3456", error: "...error message.."}
+        {"phase": "export", "executed": "false", "succeeded": false, "durationInMs": "0"}
+        ...
+    ],
+    "buildpacks": [
+        {"id": "paketo-buildpacks/maven", "executed": "true", "succeeded": true, "durationInMs": "3456"},
+        {"id": "paketo-buildpacks/openjdk", "executed": "true", "succeeded": true, "durationInMs": "3456"},
+        {"id": "paketo-buildpacks/executable-jar", "executed": "true", "succeeded": false, "durationInMs": "3456", error: "...error message..."},
+        {"id": "paketo-buildpacks/syft", "executed": "false", "succeeded": false, "durationInMs": "0"}
+        ...
+    ]
+}
+```
+
+Meanwhile, a `collect` phase should be supported by buildpack extension to collect the report file.
+
+# Prior Art
+[prior-art]: #prior-art
+
+N/A
+
+# Unresolved Questions
+[unresolved-questions]: #unresolved-questions
+
+N/A
+
+
+# History
+[history]: #history
+
+N/A