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test(metrics): Improve testability of @FlushMetrics annotation (#2112)
* Clarify how to mock the Lambda context in unit tests for Metrics utility. * Revert when() mocking in documentation. * Avoid metrics from raising an exception when using plain mocked Lambda context. * Reset outputstream in unit test docs. * Make stdout stream field static and final. * Fix issue when function name is not set. * Fix hl_lines in docs. * Fix hl_lines in docs. * Remove java8 from sam templates.
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‎docs/core/metrics.md‎

Lines changed: 48 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -140,7 +140,7 @@ For most use-cases, we recommend using Environment variables and only overwrite
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Type: AWS::Serverless::Function
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Properties:
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...
143-
Runtime: java8
143+
Runtime: java11
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Environment:
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Variables:
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POWERTOOLS_SERVICE_NAME: payment
@@ -558,9 +558,24 @@ If you would like to suppress metrics output during your unit tests, you can use
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When unit testing your code, you can run assertions against the output generated by the `Metrics` Singleton. For the `EmfMetricsLogger`, you can assert the generated JSON blob following the [CloudWatch EMF specification](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/CloudWatch_Embedded_Metric_Format.html) against your expected output.
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Make sure to set a test metrics namespace and service name to run assertions against metrics. For example, by setting the following environment variables in your tests:
562+
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```xml
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<plugin>
565+
<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-surefire-plugin</artifactId>
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<configuration>
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<environmentVariables>
569+
<POWERTOOLS_SERVICE_NAME>TestService</POWERTOOLS_SERVICE_NAME>
570+
<POWERTOOLS_METRICS_NAMESPACE>TestNamespace</POWERTOOLS_METRICS_NAMESPACE>
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</environmentVariables>
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</configuration>
573+
</plugin>
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```
575+
561576
Consider the following example where we redirect the standard output to a custom `PrintStream`. We use the Jackson library to parse the EMF output into a `JsonNode` and run assertions against that.
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563-
```java hl_lines="23 28 33 50-55"
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```java hl_lines="35 40 56-72"
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import static org.assertj.core.api.Assertions.assertThat;
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import java.io.ByteArrayOutputStream;
@@ -571,56 +586,73 @@ import java.util.Map;
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import org.junit.jupiter.api.AfterEach;
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import org.junit.jupiter.api.BeforeEach;
573588
import org.junit.jupiter.api.Test;
589+
import org.junit.jupiter.api.extension.ExtendWith;
590+
import org.mockito.Mock;
591+
import org.mockito.junit.jupiter.MockitoExtension;
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575593
import com.amazonaws.services.lambda.runtime.Context;
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import com.amazonaws.services.lambda.runtime.RequestHandler;
577595
import com.fasterxml.jackson.databind.JsonNode;
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import com.fasterxml.jackson.databind.ObjectMapper;
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import software.amazon.lambda.powertools.metrics.model.MetricUnit;
581-
import software.amazon.lambda.powertools.metrics.testutils.TestContext;
582599

600+
@ExtendWith(MockitoExtension.class)
583601
class MetricsTestExample {
584602

603+
@Mock
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Context lambdaContext;
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585606
private final PrintStream standardOut = System.out;
586-
private final ByteArrayOutputStream outputStreamCaptor = new ByteArrayOutputStream();
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private ByteArrayOutputStream outputStreamCaptor;
587608
private final ObjectMapper objectMapper = new ObjectMapper();
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@BeforeEach
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void setUp() {
612+
outputStreamCaptor = new ByteArrayOutputStream();
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System.setOut(new PrintStream(outputStreamCaptor));
592614
}
593615

594616
@AfterEach
595-
void tearDown() {
617+
void tearDown() throws Exception {
596618
System.setOut(standardOut);
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}
598620

599621
@Test
600622
void shouldCaptureMetricsFromAnnotatedHandler() throws Exception {
601623
// Given
602624
RequestHandler<Map<String, Object>, String> handler = new HandlerWithMetricsAnnotation();
603-
Context context = new TestContext();
604625
Map<String, Object> input = new HashMap<>();
605626

606627
// When
607-
handler.handleRequest(input, context);
628+
handler.handleRequest(input, lambdaContext);
608629

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// Then
610631
String emfOutput = outputStreamCaptor.toString().trim();
611-
JsonNode rootNode = objectMapper.readTree(emfOutput);
612-
613-
assertThat(rootNode.has("test-metric")).isTrue();
614-
assertThat(rootNode.get("test-metric").asDouble()).isEqualTo(100.0);
615-
assertThat(rootNode.get("_aws").get("CloudWatchMetrics").get(0).get("Namespace").asText())
616-
.isEqualTo("CustomNamespace");
617-
assertThat(rootNode.has("Service")).isTrue();
618-
assertThat(rootNode.get("Service").asText()).isEqualTo("CustomService");
632+
String[] jsonLines = emfOutput.split("\n");
633+
634+
// First JSON object should be the cold start metric
635+
JsonNode coldStartNode = objectMapper.readTree(jsonLines[0]);
636+
assertThat(coldStartNode.has("ColdStart")).isTrue();
637+
assertThat(coldStartNode.get("ColdStart").asDouble()).isEqualTo(1.0);
638+
assertThat(coldStartNode.get("_aws").get("CloudWatchMetrics").get(0).get("Namespace").asText())
639+
.isEqualTo("TestNamespace");
640+
assertThat(coldStartNode.has("Service")).isTrue();
641+
assertThat(coldStartNode.get("Service").asText()).isEqualTo("TestService");
642+
643+
// Second JSON object should be the regular metric
644+
JsonNode regularNode = objectMapper.readTree(jsonLines[1]);
645+
assertThat(regularNode.has("test-metric")).isTrue();
646+
assertThat(regularNode.get("test-metric").asDouble()).isEqualTo(100.0);
647+
assertThat(regularNode.get("_aws").get("CloudWatchMetrics").get(0).get("Namespace").asText())
648+
.isEqualTo("TestNamespace");
649+
assertThat(regularNode.has("Service")).isTrue();
650+
assertThat(regularNode.get("Service").asText()).isEqualTo("TestService");
619651
}
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621653
static class HandlerWithMetricsAnnotation implements RequestHandler<Map<String, Object>, String> {
622654
@Override
623-
@FlushMetrics(namespace = "CustomNamespace", service = "CustomService")
655+
@FlushMetrics(captureColdStart = true)
624656
public String handleRequest(Map<String, Object> input, Context context) {
625657
Metrics metrics = MetricsFactory.getMetricsInstance();
626658
metrics.addMetric("test-metric", 100, MetricUnit.COUNT);

‎docs/core/tracing.md‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -105,7 +105,7 @@ Before your use this utility, your AWS Lambda function [must have permissions](h
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Type: AWS::Serverless::Function
106106
Properties:
107107
...
108-
Runtime: java8
108+
Runtime: java11
109109

110110
Tracing: Active
111111
Environment:
@@ -191,7 +191,7 @@ different supported `captureMode` to record response, exception or both.
191191
Type: AWS::Serverless::Function
192192
Properties:
193193
...
194-
Runtime: java8
194+
Runtime: java11
195195

196196
Tracing: Active
197197
Environment:

‎powertools-metrics/pom.xml‎

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Original file line numberDiff line numberDiff line change
@@ -105,6 +105,11 @@
105105
<artifactId>assertj-core</artifactId>
106106
<scope>test</scope>
107107
</dependency>
108+
<dependency>
109+
<groupId>org.mockito</groupId>
110+
<artifactId>mockito-junit-jupiter</artifactId>
111+
<scope>test</scope>
112+
</dependency>
108113
<dependency>
109114
<groupId>software.amazon.lambda</groupId>
110115
<artifactId>powertools-common</artifactId>
@@ -135,6 +140,13 @@
135140
</profile>
136141
<profile>
137142
<id>generate-graalvm-files</id>
143+
<dependencies>
144+
<dependency>
145+
<groupId>org.mockito</groupId>
146+
<artifactId>mockito-subclass</artifactId>
147+
<scope>test</scope>
148+
</dependency>
149+
</dependencies>
138150
<build>
139151
<plugins>
140152
<plugin>
@@ -154,6 +166,13 @@
154166
</profile>
155167
<profile>
156168
<id>graalvm-native</id>
169+
<dependencies>
170+
<dependency>
171+
<groupId>org.mockito</groupId>
172+
<artifactId>mockito-subclass</artifactId>
173+
<scope>test</scope>
174+
</dependency>
175+
</dependencies>
157176
<build>
158177
<plugins>
159178
<plugin>

‎powertools-metrics/src/main/java/software/amazon/lambda/powertools/metrics/internal/EmfMetricsLogger.java‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -204,7 +204,7 @@ public void captureColdStartMetric(Context context,
204204
}
205205

206206
// Add request ID from context if available
207-
if (context != null) {
207+
if (context != null && context.getAwsRequestId() != null) {
208208
coldStartLogger.putProperty(REQUEST_ID_PROPERTY, context.getAwsRequestId());
209209
}
210210

‎powertools-metrics/src/main/java/software/amazon/lambda/powertools/metrics/internal/LambdaMetricsAspect.java‎

Lines changed: 7 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -113,7 +113,10 @@ private void captureColdStartMetricIfEnabled(Context extractedContext, FlushMetr
113113
}
114114

115115
Metrics metricsInstance = MetricsFactory.getMetricsInstance();
116-
metricsInstance.addMetadata(REQUEST_ID_PROPERTY, extractedContext.getAwsRequestId());
116+
// This can be null e.g. during unit tests when mocking the Lambda context
117+
if (extractedContext.getAwsRequestId() != null) {
118+
metricsInstance.addMetadata(REQUEST_ID_PROPERTY, extractedContext.getAwsRequestId());
119+
}
117120

118121
// Only capture cold start metrics if enabled on annotation
119122
if (metrics.captureColdStart()) {
@@ -133,8 +136,9 @@ private void captureColdStartMetricIfEnabled(Context extractedContext, FlushMetr
133136
}
134137

135138
// Add function name
136-
coldStartDimensions.addDimension("FunctionName",
137-
funcName != null ? funcName : extractedContext.getFunctionName());
139+
if (funcName != null) {
140+
coldStartDimensions.addDimension("FunctionName", funcName);
141+
}
138142

139143
metricsInstance.captureColdStartMetric(extractedContext, coldStartDimensions);
140144
}

‎powertools-metrics/src/test/java/software/amazon/lambda/powertools/metrics/RequestHandlerTest.java‎

Lines changed: 126 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,126 @@
1+
package software.amazon.lambda.powertools.metrics;
2+
3+
import static org.assertj.core.api.Assertions.assertThat;
4+
5+
import java.io.ByteArrayOutputStream;
6+
import java.io.PrintStream;
7+
import java.lang.reflect.Method;
8+
import java.util.HashMap;
9+
import java.util.Map;
10+
11+
import org.junit.jupiter.api.AfterEach;
12+
import org.junit.jupiter.api.BeforeEach;
13+
import org.junit.jupiter.api.Test;
14+
import org.junit.jupiter.api.extension.ExtendWith;
15+
import org.junitpioneer.jupiter.SetEnvironmentVariable;
16+
import org.mockito.Mock;
17+
import org.mockito.junit.jupiter.MockitoExtension;
18+
19+
import com.amazonaws.services.lambda.runtime.Context;
20+
import com.amazonaws.services.lambda.runtime.RequestHandler;
21+
import com.fasterxml.jackson.databind.JsonNode;
22+
import com.fasterxml.jackson.databind.ObjectMapper;
23+
24+
import software.amazon.lambda.powertools.common.internal.LambdaHandlerProcessor;
25+
import software.amazon.lambda.powertools.metrics.model.MetricUnit;
26+
27+
@ExtendWith(MockitoExtension.class)
28+
class RequestHandlerTest {
29+
30+
// For developer convenience, no exceptions should be thrown when using a plain Lambda Context mock
31+
@Mock
32+
Context lambdaContext;
33+
34+
private static final PrintStream STDOUT = System.out;
35+
private ByteArrayOutputStream outputStreamCaptor;
36+
private final ObjectMapper objectMapper = new ObjectMapper();
37+
38+
@BeforeEach
39+
void setUp() throws Exception {
40+
outputStreamCaptor = new ByteArrayOutputStream();
41+
System.setOut(new PrintStream(outputStreamCaptor));
42+
43+
// Reset LambdaHandlerProcessor's SERVICE_NAME
44+
Method resetServiceName = LambdaHandlerProcessor.class.getDeclaredMethod("resetServiceName");
45+
resetServiceName.setAccessible(true);
46+
resetServiceName.invoke(null);
47+
48+
// Reset IS_COLD_START
49+
java.lang.reflect.Field coldStartField = LambdaHandlerProcessor.class.getDeclaredField("IS_COLD_START");
50+
coldStartField.setAccessible(true);
51+
coldStartField.set(null, null);
52+
}
53+
54+
@AfterEach
55+
void tearDown() throws Exception {
56+
System.setOut(STDOUT);
57+
58+
// Reset the singleton state between tests
59+
java.lang.reflect.Field field = MetricsFactory.class.getDeclaredField("metrics");
60+
field.setAccessible(true);
61+
field.set(null, null);
62+
63+
field = MetricsFactory.class.getDeclaredField("provider");
64+
field.setAccessible(true);
65+
field.set(null, new software.amazon.lambda.powertools.metrics.provider.EmfMetricsProvider());
66+
}
67+
68+
@Test
69+
@SetEnvironmentVariable(key = "POWERTOOLS_METRICS_NAMESPACE", value = "TestNamespace")
70+
@SetEnvironmentVariable(key = "POWERTOOLS_SERVICE_NAME", value = "TestService")
71+
void shouldCaptureMetricsFromAnnotatedHandler() throws Exception {
72+
// Given
73+
RequestHandler<Map<String, Object>, String> handler = new HandlerWithMetricsAnnotation();
74+
Map<String, Object> input = new HashMap<>();
75+
76+
// When
77+
handler.handleRequest(input, lambdaContext);
78+
79+
// Then
80+
String emfOutput = outputStreamCaptor.toString().trim();
81+
String[] jsonLines = emfOutput.split("\n");
82+
83+
// First JSON object should be the cold start metric
84+
JsonNode coldStartNode = objectMapper.readTree(jsonLines[0]);
85+
assertThat(coldStartNode.has("ColdStart")).isTrue();
86+
assertThat(coldStartNode.get("ColdStart").asDouble()).isEqualTo(1.0);
87+
assertThat(coldStartNode.get("_aws").get("CloudWatchMetrics").get(0).get("Namespace").asText())
88+
.isEqualTo("TestNamespace");
89+
assertThat(coldStartNode.has("Service")).isTrue();
90+
assertThat(coldStartNode.get("Service").asText()).isEqualTo("TestService");
91+
92+
// Second JSON object should be the regular metric
93+
JsonNode regularNode = objectMapper.readTree(jsonLines[1]);
94+
assertThat(regularNode.has("test-metric")).isTrue();
95+
assertThat(regularNode.get("test-metric").asDouble()).isEqualTo(100.0);
96+
assertThat(regularNode.get("_aws").get("CloudWatchMetrics").get(0).get("Namespace").asText())
97+
.isEqualTo("TestNamespace");
98+
assertThat(regularNode.has("Service")).isTrue();
99+
assertThat(regularNode.get("Service").asText()).isEqualTo("TestService");
100+
}
101+
102+
@SetEnvironmentVariable(key = "POWERTOOLS_METRICS_DISABLED", value = "true")
103+
@Test
104+
void shouldNotCaptureMetricsWhenDisabled() {
105+
// Given
106+
RequestHandler<Map<String, Object>, String> handler = new HandlerWithMetricsAnnotation();
107+
Map<String, Object> input = new HashMap<>();
108+
109+
// When
110+
handler.handleRequest(input, lambdaContext);
111+
112+
// Then
113+
String emfOutput = outputStreamCaptor.toString().trim();
114+
assertThat(emfOutput).isEmpty();
115+
}
116+
117+
static class HandlerWithMetricsAnnotation implements RequestHandler<Map<String, Object>, String> {
118+
@Override
119+
@FlushMetrics(captureColdStart = true)
120+
public String handleRequest(Map<String, Object> input, Context context) {
121+
Metrics metrics = MetricsFactory.getMetricsInstance();
122+
metrics.addMetric("test-metric", 100, MetricUnit.COUNT);
123+
return "OK";
124+
}
125+
}
126+
}

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