Fix periodic reader to trigger first exporter at the interval (#1766)

opentelemetry-otlp/examples/basic-otlp-http/README.md

@@ -32,12 +32,24 @@ docker-compose down
 If you don't want to use `docker-compose`, you can manually run the `otel/opentelemetry-collector` container
 and inspect the logs to see traces being transferred.
 
+On Unix based systems use:
+
 ```shell
 # From the current directory, run `opentelemetry-collector`
-$ docker run --rm -it -p 4318:4318 -v $(pwd):/cfg otel/opentelemetry-collector:latest --config=/cfg/otel-collector-config.yaml
+docker run --rm -it -p 4318:4318 -v $(pwd):/cfg otel/opentelemetry-collector:latest --config=/cfg/otel-collector-config.yaml
+```
+
+On Windows use:
 
-# Run the app which exports logs, metrics and traces via OTLP to the collector.
-$ cargo run
+```shell
+# From the current directory, run `opentelemetry-collector`
+docker run --rm -it -p 4318:4318 -v "%cd%":/cfg otel/opentelemetry-collector:latest --config=/cfg/otel-collector-config.yaml
+```
+
+Run the app which exports logs, metrics and traces via OTLP to the collector
+
+```shell
+cargo run
 ```
 
 ## View results

opentelemetry-otlp/examples/basic-otlp/README.md

@@ -32,12 +32,24 @@ docker-compose down
 If you don't want to use `docker-compose`, you can manually run the `otel/opentelemetry-collector` container
 and inspect the logs to see traces being transferred.
 
+On Unix based systems use:
+
 ```shell
 # From the current directory, run `opentelemetry-collector`
-$ docker run --rm -it -p 4317:4317 -v $(pwd):/cfg otel/opentelemetry-collector:latest --config=/cfg/otel-collector-config.yaml
+docker run --rm -it -p 4317:4317 -v $(pwd):/cfg otel/opentelemetry-collector:latest --config=/cfg/otel-collector-config.yaml
+```
+
+On Windows use:
 
-# Run the app which exports logs, metrics and traces via OTLP to the collector.
-$ cargo run
+```shell
+# From the current directory, run `opentelemetry-collector`
+docker run --rm -it -p 4317:4317 -v "%cd%":/cfg otel/opentelemetry-collector:latest --config=/cfg/otel-collector-config.yaml
+```
+
+Run the app which exports logs, metrics and traces via OTLP to the collector
+
+```shell
+cargo run
 ```
 
 ## View results

opentelemetry-otlp/examples/basic-otlp/src/main.rs

@@ -114,7 +114,6 @@ async fn main() -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
     for _ in 0..10 {
         counter.add(1, &[KeyValue::new("test_key", "test_value")]);
     }
-    counter.add(1, &[KeyValue::new("test_key", "test_value")]);
 
     tracer.in_span("Main operation", |cx| {
         let span = cx.span();

opentelemetry-sdk/CHANGELOG.md

@@ -7,6 +7,9 @@
   [1612](https://github.com/open-telemetry/opentelemetry-rust/pull/1612/files)
 - [#1422](https://github.com/open-telemetry/opentelemetry-rust/pull/1422)
   Fix metrics aggregation bug when using Views to drop attributes.
+- [#1766](https://github.com/open-telemetry/opentelemetry-rust/pull/1766)
+  Fix Metrics PeriodicReader to trigger first collect/export at the first interval
+  instead of doing it right away.
 - [#1623](https://github.com/open-telemetry/opentelemetry-rust/pull/1623) Add Drop implementation for SdkMeterProvider,
   which shuts down metricreaders, thereby allowing metrics still in memory to be flushed out.
 - **Breaking** [#1624](https://github.com/open-telemetry/opentelemetry-rust/pull/1624) Remove `OsResourceDetector` and

opentelemetry-sdk/src/metrics/periodic_reader.rs

@@ -132,6 +132,7 @@ where
             let ticker = self
                 .runtime
                 .interval(self.interval)
+                .skip(1) // The ticker is fired immediately, so we should skip the first one to align with the interval.
                 .map(|_| Message::Export);
 
             let messages = Box::pin(stream::select(message_receiver, ticker));