Address review feedback

object_store/src/aws/client.rs

@@ -641,7 +641,7 @@ impl S3Client {
             PutPartPayload::Part(payload) => request.with_payload(payload),
             PutPartPayload::Copy(path) => request.header(
                 "x-amz-copy-source",
-                &format!("{}/{}", self.config.bucket, path),
+                &format!("{}/{}", self.config.bucket, encode_path(path)),
             ),
         };
 
@@ -671,6 +671,16 @@ impl S3Client {
         Ok(PartId { content_id })
     }
 
+    pub(crate) async fn abort_multipart(&self, location: &Path, upload_id: &str) -> Result<()> {
+        self.request(Method::DELETE, location)
+            .query(&[("uploadId", upload_id)])
+            .with_encryption_headers()
+            .send()
+            .await?;
+
+        Ok(())
+    }
+
     pub(crate) async fn complete_multipart(
         &self,
         location: &Path,

object_store/src/aws/mod.rs

@@ -302,27 +302,40 @@ impl ObjectStore for AmazonS3 {
                     .client
                     .create_multipart(to, PutMultipartOpts::default())
                     .await?;
-                let part_id = self
-                    .client
-                    .put_part(to, &upload_id, 0, PutPartPayload::Copy(from))
-                    .await?;
-                let res = match self
-                    .client
-                    .complete_multipart(
-                        to,
-                        &upload_id,
-                        vec![part_id],
-                        CompleteMultipartMode::Create,
-                    )
-                    .await
-                {
-                    Err(e @ Error::Precondition { .. }) => Err(Error::AlreadyExists {
-                        path: to.to_string(),
-                        source: Box::new(e),
-                    }),
-                    Ok(_) => Ok(()),
-                    Err(e) => Err(e.into()),
-                };
+
+                let res = async {
+                    let part_id = self
+                        .client
+                        .put_part(to, &upload_id, 0, PutPartPayload::Copy(from))
+                        .await?;
+                    match self
+                        .client
+                        .complete_multipart(
+                            to,
+                            &upload_id,
+                            vec![part_id],
+                            CompleteMultipartMode::Create,
+                        )
+                        .await
+                    {
+                        Err(e @ Error::Precondition { .. }) => Err(Error::AlreadyExists {
+                            path: to.to_string(),
+                            source: Box::new(e),
+                        }),
+                        Ok(_) => Ok(()),
+                        Err(e) => Err(e.into()),
+                    }
+                }
+                .await;
+
+                // If the multipart upload failed, make a best effort attempt to
+                // clean it up. It's the caller's responsibility to add a
+                // lifecycle rule if guaranteed cleanup is required, as we
+                // cannot protect against an ill-timed process crash.
+                if res.is_err() {
+                    let _ = self.client.abort_multipart(to, &upload_id).await;
+                }
+
                 return res;
             }
             Some(S3CopyIfNotExists::Dynamo(lock)) => {

object_store/src/aws/precondition.rs

@@ -47,11 +47,17 @@ pub enum S3CopyIfNotExists {
     /// Encoded as `header-with-status:<HEADER_NAME>:<HEADER_VALUE>:<STATUS>` ignoring whitespace
     HeaderWithStatus(String, String, reqwest::StatusCode),
     /// Native Amazon S3 supports copy if not exists through a multipart upload
-    /// where the upload copies an existing object and is completed only if
-    /// the new object does not already exist.
+    /// where the upload copies an existing object and is completed only if the
+    /// new object does not already exist.
     ///
-    /// WARNING: When using this mode, `copy_if_not_exists` does not copy
-    /// tags or attributes from the source object.
+    /// WARNING: When using this mode, `copy_if_not_exists` does not copy tags
+    /// or attributes from the source object.
+    ///
+    /// WARNING: When using this mode, `copy_if_not_exists` makes only a best
+    /// effort attempt to clean up the multipart upload if the copy operation
+    /// fails. Consider using a lifecycle rule to automatically clean up
+    /// abandoned multipart uploads. See [the module
+    /// docs](super#multipart-uploads) for details.
     ///
     /// Encoded as `multipart` ignoring whitespace.
     Multipart,