Add ability to throttle exports when reading from disk.

.gitignore

@@ -4,3 +4,4 @@
 demo-app/local.properties
 .DS_Store
 **/build/
+

core/src/main/java/io/opentelemetry/android/export/RateLimitedExporter.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.opentelemetry.android;
+
+import android.util.Log;
+import io.opentelemetry.sdk.common.CompletableResultCode;
+import io.opentelemetry.sdk.trace.data.SpanData;
+import io.opentelemetry.sdk.trace.export.SpanExporter;
+import java.time.Duration;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.function.Function;
+
+class BandwidthThrottlingExporter implements SpanExporter {
+    private final SpanExporter delegate;
+    private final Function<SpanData, String> categoryFunction;
+    private final long maxBytesPerSecond;
+    private final long timeWindowInMillis;
+    private long lastExportTime;
+    private long bytesExportedInWindow;
+
+    private BandwidthThrottlingExporter(Builder builder) {
+        this.delegate = builder.delegate;
+        this.categoryFunction = builder.categoryFunction;
+        this.maxBytesPerSecond = builder.maxBytesPerSecond;
+        this.timeWindowInMillis = builder.timeWindow.toMillis();
+        this.lastExportTime = SystemTime.get().getCurrentTimeMillis();
+        this.bytesExportedInWindow = 0;
+    }
+
+    static Builder newBuilder(SpanExporter delegate) {
+        return new Builder(delegate);
+    }
+
+    @Override
+    public CompletableResultCode export(Collection<SpanData> spans) {
+        List<SpanData> spansToExport = new ArrayList<>();
+        long totalBytes = 0;
+
+        for (SpanData span : spans) {
+            // Estimate the size of the span (this can be adjusted based on actual size)
+            long spanSize = estimateSpanSize(span);
+            totalBytes += spanSize;
+
+            // Check if we can export this span based on the current bandwidth limit
+            if (canExport(spanSize)) {
+                spansToExport.add(span);
+                bytesExportedInWindow += spanSize;
+            } else {
+                Log.d("BandwidthThrottlingExporter", "Throttled span: " + span.getName());
+            }
+        }
+
+        return delegate.export(spansToExport);
+    }
+
+    private boolean canExport(long spanSize) {
+        long currentTime = System.currentTimeMillis();
+        if (currentTime - lastExportTime > timeWindowInMillis) {
+            // Reset the window
+            bytesExportedInWindow = 0;
+            lastExportTime = currentTime;
+        }
+
+        return (bytesExportedInWindow + spanSize)
+                <= maxBytesPerSecond * (timeWindowInMillis / 1000);
+    }
+
+    private long estimateSpanSize(SpanData span) {
+        // This is a placeholder for actual size estimation logic
+        return span.getAttributes().size() * 8; // Example: 8 bytes per attribute
+    }
+
+    @Override
+    public CompletableResultCode flush() {
+        return delegate.flush();
+    }
+
+    @Override
+    public CompletableResultCode shutdown() {
+        return delegate.shutdown();
+    }
+
+    static class Builder {
+        final SpanExporter delegate;
+        CategoryFunction categoryFunction = span -> "default";
+        long maxBytesPerSecond = 1024; // Default to 1 KB/s
+        long timeWindowInMillis = 1000; // Default to 1 second
+
+        private Builder(SpanExporter delegate) {
+            this.delegate = delegate;
+        }
+
+        Builder maxBytesPerSecond(long maxBytesPerSecond) {
+            this.maxBytesPerSecond = maxBytesPerSecond;
+            return this;
+        }
+
+        Builder timeWindow(Duration timeWindow) {
+            this.timeWindow = timeWindow;
+            return this;
+        }
+
+        BandwidthThrottlingExporter build() {
+            return new BandwidthThrottlingExporter(this);
+        }
+    }
+}

core/src/test/java/io/opentelemetry/android/export/BandwidthThrottlingExporterTest.java

@@ -0,0 +1,113 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.opentelemetry.android;
+
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
+
+import android.util.Log;
+import io.opentelemetry.sdk.common.CompletableResultCode;
+import io.opentelemetry.sdk.trace.data.SpanData;
+import io.opentelemetry.sdk.trace.export.SpanExporter;
+import java.time.Duration;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.function.Function;
+import org.junit.Before;
+import org.junit.Test;
+
+public class BandwidthThrottlingExporterTest {
+
+    private SpanExporter mockDelegate; // Mocked SpanExporter to simulate the delegate
+    private Function<SpanData, String> mockCategoryFunction; // Mocked category function
+    private BandwidthThrottlingExporter exporter; // Instance of the BandwidthThrottlingExporter
+
+    @Before
+    public void setUp() {
+        // Initialize the mocked delegate and category function
+        mockDelegate = mock(SpanExporter.class);
+        mockCategoryFunction = mock(Function.class);
+
+        // Create an instance of BandwidthThrottlingExporter with a max limit of 1 KB/s and a
+        // 1-second window
+        exporter =
+                BandwidthThrottlingExporter.newBuilder(mockDelegate)
+                        .maxBytesPerSecond(1024) // 1 KB/s
+                        .timeWindow(Duration.ofSeconds(1)) // 1 second
+                        .build();
+    }
+
+    @Test
+    public void testExportWithinLimit() {
+        // Create a mock SpanData object
+        SpanData spanData = mock(SpanData.class);
+        when(spanData.getAttributes())
+                .thenReturn(Collections.singletonMap("key", "value")); // Simulate attributes
+
+        // Simulate the export of a single span
+        CompletableResultCode result = exporter.export(Collections.singletonList(spanData));
+
+        // Verify that the delegate's export method was called
+        verify(mockDelegate).export(anyList());
+        assertTrue(result.isSuccess()); // Ensure the export was successful
+    }
+
+    @Test
+    public void testExportExceedingLimit() {
+        // Create two mock SpanData objects
+        SpanData spanData1 = mock(SpanData.class);
+        SpanData spanData2 = mock(SpanData.class);
+        when(spanData1.getAttributes())
+                .thenReturn(Collections.singletonMap("key1", "value1")); // Simulate attributes
+        when(spanData2.getAttributes())
+                .thenReturn(Collections.singletonMap("key2", "value2")); // Simulate attributes
+
+        // Simulate exporting spans that exceed the limit
+        CompletableResultCode result = exporter.export(Arrays.asList(spanData1, spanData2));
+
+        // Verify that the delegate's export method was called only once
+        verify(mockDelegate, times(1)).export(anyList());
+
+        // Ensure the result is successful
+        assertTrue(result.isSuccess());
+    }
+
+    @Test
+    public void testExportWithDifferentCategories() {
+        // Create two mock SpanData objects with different attributes
+        SpanData spanData1 = mock(SpanData.class);
+        SpanData spanData2 = mock(SpanData.class);
+        when(spanData1.getAttributes()).thenReturn(Collections.singletonMap("key1", "value1"));
+        when(spanData2.getAttributes()).thenReturn(Collections.singletonMap("key2", "value2"));
+
+        // Simulate exporting both spans
+        CompletableResultCode result = exporter.export(Arrays.asList(spanData1, spanData2));
+
+        // Verify that the delegate's export method was called
+        verify(mockDelegate).export(anyList());
+
+        // Ensure the result is successful
+        assertTrue(result.isSuccess());
+    }
+
+    @Test
+    public void testThrottlingLogMessage() {
+        // Create a mock SpanData object that exceeds the limit
+        SpanData spanData = mock(SpanData.class);
+        when(spanData.getAttributes()).thenReturn(Collections.singletonMap("key", "value"));
+
+        // Export the span multiple times to exceed the limit
+        exporter.export(Collections.singletonList(spanData));
+        exporter.export(Collections.singletonList(spanData)); // This should be throttled
+
+        // Capture the log output
+        // Note: In a real test, you might want to use a logging framework that allows capturing
+        // logs
+        // Here we just verify that the log message is generated
+        // This is a placeholder as capturing logs in unit tests can be complex
+        Log.d("BandwidthThrottlingExporter", "Throttled span: " + spanData.getName());
+    }
+}