Add prometheus mode to obsagent-client test module (Azure#5147)

The main change in this PR is the addition of a new Prometheus mode in the obsagent-client module. In this mode, the client hosts a prometheus endpoint from which 3 example metrics (a counter, guage, and histogram) can be pulled periodically.  The endpoint is configurable via the PROMETHEUS_ENDPOINT env variable.

Other changes:
1. Move OTel mode code into otel_client module
2. Move config code into a config module
3. Create new prometheus_server module
4. Add Cargo feature flags for the two modes (prom and otel)
5. Upgrade from opentelemetry-0.13 and optentelemetry-otlp-0.6 to opentelemetry-0.15 and opentelemetry-otlp-0.8

builds/checkin/rust-test-modules.yaml

@@ -56,9 +56,19 @@ jobs:
       - bash: scripts/linux/generic-rust/clippy.sh --project-root "test/modules/generic-mqtt-tester"
         displayName: Clippy (Generic MQTT Tester)
 
-      - bash: scripts/linux/generic-rust/build.sh --project-root "test/modules/obsagent-client" --packages "Cargo.toml" --manifest-path
-        displayName: Build Observability-Agent Client Module           
+      - bash: >
+          scripts/linux/generic-rust/build.sh --project-root "test/modules/obsagent-client" 
+          --packages "Cargo.toml" --manifest-path --no-default-features --features prom
+        displayName: Build ObsAgent Client Module (Prometheus mode)
+      - bash: >
+          scripts/linux/generic-rust/build.sh --project-root "test/modules/obsagent-client" 
+          --packages "Cargo.toml" --manifest-path --no-default-features --features otel
+        displayName: Build ObsAgent Client Module (OpenTelemetry mode)        
+      - bash: >
+          scripts/linux/generic-rust/build.sh --project-root "test/modules/obsagent-client" 
+          --packages "Cargo.toml" --manifest-path --no-default-features --features "prom otel"
+        displayName: Build ObsAgent Client Module (Prom & OTel)
       - bash: scripts/linux/generic-rust/format.sh --project-root "test/modules/obsagent-client"
-        displayName: Format Code (Observability-Agent Client)
+        displayName: Format Code (ObsAgent Client)
       - bash: scripts/linux/generic-rust/clippy.sh --project-root "test/modules/obsagent-client"
-        displayName: Clippy (Observability-Agent Client)
+        displayName: Clippy (ObsAgent Client)

builds/misc/images.yaml

@@ -238,7 +238,7 @@ jobs:
       - template: templates/rust-test-module-images.yaml
         parameters:
           module.path: 'test/modules/obsagent-client'
-          module.name: 'obsagent-client'        
+          module.name: 'obsagent-client'     
 
 ################################################################################
   - job: manifest

builds/misc/templates/rust-test-module-build.yaml

@@ -18,14 +18,20 @@ steps:
     displayName: Build observability-agent client - amd64
     inputs:
       filePath: scripts/linux/cross-platform-rust-build.sh
-      arguments: --os alpine --arch amd64 --build-path test/modules/obsagent-client
+      arguments: >
+        --os alpine --arch amd64 --build-path test/modules/obsagent-client
+        --cargo-flags "--no-default-features --features otel,prom"
   - task: Bash@3
     displayName: Build observability-agent client - arm32
     inputs:
       filePath: scripts/linux/cross-platform-rust-build.sh
-      arguments: --os ubuntu18.04 --arch arm32v7 --build-path test/modules/obsagent-client
+      arguments: >
+        --os ubuntu18.04 --arch arm32v7 --build-path test/modules/obsagent-client
+        --cargo-flags "--no-default-features --features otel,prom"
   - task: Bash@3
     displayName: Build observability-agent client - arm64
     inputs:
       filePath: scripts/linux/cross-platform-rust-build.sh
-      arguments: --os ubuntu18.04 --arch aarch64 --build-path test/modules/obsagent-client
+      arguments: >
+        --os ubuntu18.04 --arch aarch64 --build-path test/modules/obsagent-client
+        --cargo-flags "--no-default-features --features otel,prom"

test/modules/obsagent-client/Cargo.toml

@@ -6,15 +6,24 @@ edition = "2018"
 description = "Test module that connects to the IoT Edge Observability Agent for benchmarking and testing purposes."
 
 [dependencies]
+anyhow = "1.0"
+cfg-if = "1.0"
 clap = "2"
 futures = "0.3"
-lazy_static = "1.4"
-opentelemetry = { version = "0.13", features = ["rt-tokio", "metrics", "serialize"] }
-opentelemetry-otlp = { version = "0.6", features = ["tonic", "metrics"] }
+hyper = { version = "0.14", features = ["http1", "runtime", "server"], optional = true }
+opentelemetry = { version = "0.15", features = ["rt-tokio", "metrics", "serialize"], optional = true }
+opentelemetry-otlp = { version = "0.8", features = ["tonic", "metrics"], optional = true }
+prometheus = { version = "0.12", optional = true }
 rand = "0.8"
 serde_json = "1.0"
 signal-hook = "0.3"
+thiserror = "1.0"
 tokio = { version = "1.0", features = ["rt-multi-thread", "macros"] }
 tracing = "0.1"
 tracing-futures = "0.2"
-tracing-subscriber = "0.2"
+tracing-subscriber = "0.2"
+
+[features]
+default = ["prom"]
+otel = ["opentelemetry", "opentelemetry-otlp"]
+prom = ["hyper", "prometheus"]