Make allSettled usage safer

allSettled does not follow the usuage fullfil pattern: it will never
reject, and always fullfil with an array of the results of each
promises.

This is not an issue in the case of lifecycle, where we actually ignore
all errors; but it makes the code look inconsistent, as it suggests
errors are possible but not handle them.

To avoid future issues, add proper processing of the results of
allSettled to build a single error when appropriate.

Issue: BB-641

Author: francoisferrand

extensions/lifecycle/tasks/LifecycleTask.js

@@ -429,7 +429,7 @@ class LifecycleTask extends BackbeatTask {
 
             // if no versions to process, skip further processing for this batch
             if (allVersionsWithStaleDate.length === 0) {
-                return Promise.allSettled(promises).then(() => done(), done);
+                return Promise.allSettled(promises).then(() => done());
             }
 
             // for each version, get their relative rules, compare with
@@ -457,7 +457,9 @@ class LifecycleTask extends BackbeatTask {
                     return resolve();
                 })));
 
-            return Promise.allSettled(promises).then(() => done(), done);
+            return Promise.allSettled(promises).then(results => done(
+                results.findLast(r => r.status === 'rejected')?.reason
+            ));
         });
     }
 

extensions/lifecycle/tasks/LifecycleTaskV2.js

@@ -114,7 +114,7 @@ class LifecycleTaskV2 extends LifecycleTask {
         return this.backbeatMetadataProxy.listLifecycle(listType, params, log,
         (err, contents, isTruncated, markerInfo) => {
             if (err) {
-                return Promise.allSettled(promises).then(() => done(err), () => done(err));
+                return Promise.allSettled(promises).then(() => done(err));
             }
 
             // re-queue truncated listing only once.
@@ -145,7 +145,9 @@ class LifecycleTaskV2 extends LifecycleTask {
                 bucketData, bucketLCRules, contents, log,
             ));
 
-            return Promise.allSettled(promises).then(() => done(), done);
+            return Promise.allSettled(promises).then(results => done(
+                results.findLast(r => r.status === 'rejected')?.reason
+            ));
         });
     }
 
@@ -195,7 +197,7 @@ class LifecycleTaskV2 extends LifecycleTask {
         return this.backbeatMetadataProxy.listLifecycle(listType, params, log,
         (err, contents, isTruncated, markerInfo) => {
             if (err) {
-                return Promise.allSettled(promises).then(() => done(err), () => done(err));
+                return Promise.allSettled(promises).then(() => done(err));
             }
 
             // create Set of unique keys not matching the next marker to
@@ -255,7 +257,9 @@ class LifecycleTaskV2 extends LifecycleTask {
                     return resolve();
                 })));
 
-            return Promise.allSettled(promises).then(() => done(), done);
+            return Promise.allSettled(promises).then(results => done(
+                results.findLast(r => r.status === 'rejected')?.reason
+            ));
         });
     }