1 files changed, 183 insertions, 0 deletions
diff --git a/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/package-info.java b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/package-info.java
index cbb6e16..110ab73 100644
--- a/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/package-info.java
+++ b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/package-info.java
@@ -1,5 +1,188 @@
 /**
  * Provides structured logging to standard output according to the Google Cloud Logging
  * specification.
+ *
+ * <ul>
+ *   <li><a href="#sect-summary">Summary</a>
+ *   <li><a href="#sect-activation">Activation</a>
+ *   <li><a href="#sect-usage">Usage</a>
+ * </ul>
+ *
+ * <h2 id="sect-summary">Summary</h2>
+ *
+ * <p>This package contains a log formatter for JBoss Logging in the form of a Quarkus plugin that
+ * implements the <a href="https://cloud.google.com/logging/docs/structured-logging">Google Cloud
+ * Logging JSON format</a> on standard output.
+ *
+ * <p>It is possible to log unstructured text, structured data, or a mixture of both depending on
+ * the situation.
+ *
+ * <h2 id="sect-activation">Activation</h2>
+ *
+ * <ul>
+ *   <li><a href="#sect-activation-maven">Activation with Maven</a>
+ *   <li><a href="#sect-activation-gradle">Activation with Gradle</a>
+ * </ul>
+ *
+ * <p>Add the runtime POM to your dependency list. As long as the JAR is on the classpath at both
+ * build time and runtime, the log formatter automatically registers itself on startup.
+ *
+ * <h3 id="sect-activation-maven">Activation with Maven</h3>
+ *
+ * <pre>{@code
+ * <project>
+ *   ...
+ *
+ *   <dependencies>
+ *     ...
+ *
+ *     <dependency>
+ *       <groupId>eu.mulk.quarkus-googlecloud-jsonlogging</groupId>
+ *       <artifactId>quarkus-googlecloud-jsonlogging</artifactId>
+ *       <version>3.1.0</version>
+ *     </dependency>
+ *
+ *     ...
+ *   </dependencies>
+ *
+ *   ...
+ * </project>
+ * }</pre>
+ *
+ * <h3 id="sect-activation-gradle">Activation with Gradle</h3>
+ *
+ * <pre>{@code
+ * dependencies {
+ *   ...
+ *
+ *   implementation("eu.mulk.quarkus-googlecloud-jsonlogging:quarkus-googlecloud-jsonlogging:3.1.0")
+ *
+ *   ...
+ * }
+ * }</pre>
+ *
+ * <h2 id="sect-usage">Usage</h2>
+ *
+ * <ul>
+ *   <li><a href="#sect-usage-parameter">Using Label and StructuredParameter</a>
+ *   <li><a href="#sect-usage-provider">Using LabelProvider and StructuredParameterProvider</a>
+ *   <li><a href="#sect-usage-mdc">Using the Mapped Diagnostic Context</a>
+ * </ul>
+ *
+ * <p>Logging unstructured data requires no code changes. All logs are automatically converted to
+ * Google-Cloud-Logging-compatible JSON.
+ *
+ * <p>Structured data can be logged in one of 3 different ways: by passing {@link
+ * eu.mulk.quarkus.googlecloud.jsonlogging.Label}s and {@link
+ * eu.mulk.quarkus.googlecloud.jsonlogging.StructuredParameter}s as parameters to individual log
+ * entries, by supplying {@link eu.mulk.quarkus.googlecloud.jsonlogging.LabelProvider}s and {@link
+ * eu.mulk.quarkus.googlecloud.jsonlogging.StructuredParameterProvider}s, or by using the Mapped
+ * Diagnostic Context.
+ *
+ * <h3 id="sect-usage-parameter">Using Label and StructuredParameter</h3>
+ *
+ * <p>Instances of {@link eu.mulk.quarkus.googlecloud.jsonlogging.Label} and {@link
+ * eu.mulk.quarkus.googlecloud.jsonlogging.StructuredParameter} can be passed as log parameters to
+ * the {@code *f} family of logging functions on JBoss Logging's {@link org.jboss.logging.Logger}.
+ *
+ * <p>Simple key–value pairs are represented by {@link
+ * eu.mulk.quarkus.googlecloud.jsonlogging.KeyValueParameter}.
+ *
+ * <p><strong>Example:</strong>
+ *
+ * <pre>{@code
+ * logger.logf(
+ *   "Request rejected: unauthorized.",
+ *   Label.of("requestId", "123"),
+ *   KeyValueParameter.of("resource", "/users/mulk"),
+ *   KeyValueParameter.of("method", "PATCH"),
+ *   KeyValueParameter.of("reason", "invalid token"));
+ * }</pre>
+ *
+ * Result:
+ *
+ * <pre>{@code
+ * {
+ *   "jsonPayload": {
+ *     "message": "Request rejected: unauthorized.",
+ *     "resource": "/users/mulk",
+ *     "method": "PATCH",
+ *     "reason": "invalid token"
+ *   },
+ *   "labels": {
+ *     "requestId": "123"
+ *   }
+ * }
+ * }</pre>
+ *
+ * <h3 id="sect-usage-provider">Using LabelProvider and StructuredParameterProvider</h3>
+ *
+ * <p>Any CDI beans that implement {@link eu.mulk.quarkus.googlecloud.jsonlogging.LabelProvider}s
+ * and {@link eu.mulk.quarkus.googlecloud.jsonlogging.StructuredParameterProvider}s are discovered
+ * at build time and consulted to provide labels and parameters for each message that is logged.
+ * This can be used to provide contextual information such as tracing and request IDs stored in
+ * thread-local storage.
+ *
+ * <p><strong>Example:</strong>
+ *
+ * <pre>{@code
+ * @Singleton
+ * @Unremovable
+ * public final class TraceLogParameterProvider implements StructuredParameterProvider, LabelProvider {
+ *
+ *   @Override
+ *   public StructuredParameter getParameter() {
+ *     var b = Json.createObjectBuilder();
+ *     b.add("traceId", Span.current().getSpanContext().getTraceId());
+ *     b.add("spanId", Span.current().getSpanContext().getSpanId());
+ *     return () -> b;
+ *   }
+ *
+ *   @Override
+ *   public Collection<Label> getLabels() {
+ *     return List.of(Label.of("requestId", "123"));
+ *   }
+ * }
+ * }</pre>
+ *
+ * Result:
+ *
+ * <pre>{@code
+ * {
+ *   "jsonPayload": {
+ *     "message": "Request rejected: unauthorized.",
+ *     "traceId": "39f9a49a9567a8bd7087b708f8932550",
+ *     "spanId": "c7431b14630b633d"
+ *   },
+ *   "labels": {
+ *     "requestId": "123"
+ *   }
+ * }
+ * }</pre>
+ *
+ * <h3 id="sect-usage-mdc">Using the Mapped Diagnostic Context</h3>
+ *
+ * <p>Any key–value pairs in JBoss Logging's thread-local {@link org.jboss.logging.MDC} are added to
+ * the resulting JSON.
+ *
+ * <p><strong>Example:</strong>
+ *
+ * <pre>{@code
+ * MDC.put("resource", "/users/mulk");
+ * MDC.put("method", "PATCH");
+ * logger.logf("Request rejected: unauthorized.");
+ * }</pre>
+ *
+ * Result:
+ *
+ * <pre>{@code
+ * {
+ *   "jsonPayload": {
+ *     "message": "Request rejected: unauthorized.",
+ *     "resource": "/users/mulk",
+ *     "method": "PATCH"
+ *   }
+ * }
+ * }</pre>
  */
 package eu.mulk.quarkus.googlecloud.jsonlogging;