Support QosException with cause (#591)

* Support QosException with cause

* Add generated changelog entries

Author: pkoenig10

changelog/@unreleased/pr-591.v2.yml

@@ -0,0 +1,5 @@
+type: feature
+feature:
+  description: '`QosException` can now be created with a cause.'
+  links:
+  - https://github.com/palantir/conjure-java-runtime-api/pull/591

errors/src/main/java/com/palantir/conjure/java/api/errors/QosException.java

@@ -38,6 +38,10 @@ private QosException(String message) {
         super(message);
     }
 
+    private QosException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
     public abstract <T> T accept(Visitor<T> visitor);
 
     public interface Visitor<T> {
@@ -56,6 +60,13 @@ public static Throttle throttle() {
         return new Throttle(Optional.empty());
     }
 
+    /**
+     * Like {@link #throttle()}, but includes a cause.
+     */
+    public static Throttle throttle(Throwable cause) {
+        return new Throttle(Optional.empty(), cause);
+    }
+
     /**
      * Like {@link #throttle()}, but additionally requests that the client wait for at least the given duration before
      * retrying the request.
@@ -64,6 +75,13 @@ public static Throttle throttle(Duration duration) {
         return new Throttle(Optional.of(duration));
     }
 
+    /**
+     * Like {@link #throttle(Duration)}, but includes a cause.
+     */
+    public static Throttle throttle(Duration duration, Throwable cause) {
+        return new Throttle(Optional.of(duration), cause);
+    }
+
     /**
      * Returns a {@link RetryOther} exception indicating that the calling client should retry against the given node of
      * this service.
@@ -72,6 +90,13 @@ public static RetryOther retryOther(URL redirectTo) {
         return new RetryOther(redirectTo);
     }
 
+    /**
+     * Like {@link #retryOther(URL)}, but includes a cause.
+     */
+    public static RetryOther retryOther(URL redirectTo, Throwable cause) {
+        return new RetryOther(redirectTo, cause);
+    }
+
     /**
      * An exception indicating that (this node of) this service is currently unavailable and the client may try again at
      * a later time, possibly against a different node of this service.
@@ -80,6 +105,13 @@ public static Unavailable unavailable() {
         return new Unavailable();
     }
 
+    /**
+     * Like {@link #unavailable()}, but includes a cause.
+     */
+    public static Unavailable unavailable(Throwable cause) {
+        return new Unavailable(cause);
+    }
+
     /** See {@link #throttle}. */
     public static final class Throttle extends QosException {
         private final Optional<Duration> retryAfter;
@@ -89,6 +121,11 @@ private Throttle(Optional<Duration> retryAfter) {
             this.retryAfter = retryAfter;
         }
 
+        private Throttle(Optional<Duration> retryAfter, Throwable cause) {
+            super("Suggesting request throttling with optional retryAfter duration: " + retryAfter, cause);
+            this.retryAfter = retryAfter;
+        }
+
         public Optional<Duration> getRetryAfter() {
             return retryAfter;
         }
@@ -108,6 +145,11 @@ private RetryOther(URL redirectTo) {
             this.redirectTo = redirectTo;
         }
 
+        private RetryOther(URL redirectTo, Throwable cause) {
+            super("Suggesting request retry against: " + redirectTo.toString(), cause);
+            this.redirectTo = redirectTo;
+        }
+
         /** Indicates an alternative URL of this service against which the request may be retried. */
         public URL getRedirectTo() {
             return redirectTo;
@@ -137,6 +179,10 @@ private Unavailable() {
             super("Server unavailable");
         }
 
+        private Unavailable(Throwable cause) {
+            super("Server unavailable", cause);
+        }
+
         @Override
         public <T> T accept(Visitor<T> visitor) {
             return visitor.visit(this);