refactor: reduce the number of failures due to conflict post update (#5604)

#### What type of PR is this?
/kind improvement
/area core
/milestone 2.14.x

#### What this PR does / why we need it:
减少文章更新因版本号冲突而失败的次数

#### Which issue(s) this PR fixes:
Fixes #5579

#### Does this PR introduce a user-facing change?
```release-note
None
```

application/src/main/java/run/halo/app/content/AbstractContentService.java

@@ -1,16 +1,19 @@
 package run.halo.app.content;
 
 import java.security.Principal;
+import java.time.Duration;
 import java.time.Instant;
 import java.util.UUID;
 import lombok.AllArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.commons.lang3.StringUtils;
+import org.springframework.dao.OptimisticLockingFailureException;
 import org.springframework.lang.Nullable;
 import org.springframework.security.core.context.ReactiveSecurityContextHolder;
 import org.springframework.security.core.context.SecurityContext;
 import org.springframework.util.Assert;
 import reactor.core.publisher.Mono;
+import reactor.util.retry.Retry;
 import run.halo.app.core.extension.content.Snapshot;
 import run.halo.app.extension.MetadataUtil;
 import run.halo.app.extension.ReactiveExtensionClient;
@@ -94,7 +97,7 @@ public abstract class AbstractContentService {
         Assert.notNull(contentRequest, "The contentRequest must not be null");
         Assert.notNull(baseSnapshotName, "The baseSnapshotName must not be null");
         Assert.notNull(contentRequest.headSnapshotName(), "The headSnapshotName must not be null");
-        return client.fetch(Snapshot.class, contentRequest.headSnapshotName())
+        return Mono.defer(() -> client.fetch(Snapshot.class, contentRequest.headSnapshotName())
                 .flatMap(headSnapshot -> client.fetch(Snapshot.class, baseSnapshotName)
                     .map(baseSnapshot -> determineRawAndContentPatch(headSnapshot, baseSnapshot,
                         contentRequest)
@@ -108,6 +111,9 @@ public abstract class AbstractContentService {
                     .defaultIfEmpty(headSnapshot)
                 )
                 .flatMap(client::update)
+            )
+            .retryWhen(Retry.backoff(5, Duration.ofMillis(100))
+                .filter(throwable -> throwable instanceof OptimisticLockingFailureException))
             .flatMap(head -> restoredContent(baseSnapshotName, head));
     }
 

application/src/main/java/run/halo/app/content/impl/PostServiceImpl.java

@@ -225,13 +225,11 @@ public class PostServiceImpl extends AbstractContentService implements PostServi
                     return client.update(post);
                 });
         }
-        return Mono.defer(() -> updateContent(baseSnapshot, postRequest.contentRequest())
+        return updateContent(baseSnapshot, postRequest.contentRequest())
             .flatMap(contentWrapper -> {
                 post.getSpec().setHeadSnapshot(contentWrapper.getSnapshotName());
                 return client.update(post);
-                }))
-            .retryWhen(Retry.backoff(5, Duration.ofMillis(100))
-                .filter(throwable -> throwable instanceof OptimisticLockingFailureException));
+            });
     }
 
     @Override

application/src/main/java/run/halo/app/content/impl/SinglePageServiceImpl.java

@@ -156,13 +156,11 @@ public class SinglePageServiceImpl extends AbstractContentService implements Sin
                     return client.update(page);
                 });
         }
-        return Mono.defer(() -> updateContent(baseSnapshot, pageRequest.contentRequest())
+        return updateContent(baseSnapshot, pageRequest.contentRequest())
             .flatMap(contentWrapper -> {
                 page.getSpec().setHeadSnapshot(contentWrapper.getSnapshotName());
                 return client.update(page);
-                }))
-            .retryWhen(Retry.backoff(5, Duration.ofMillis(100))
-                .filter(throwable -> throwable instanceof OptimisticLockingFailureException));
+            });
     }
 
     private Mono<ListedSinglePage> getListedSinglePage(SinglePage singlePage) {

application/src/main/java/run/halo/app/core/extension/endpoint/PostEndpoint.java

@@ -193,11 +193,13 @@ public class PostEndpoint implements CustomEndpoint {
     Mono<ServerResponse> updateContent(ServerRequest request) {
         String postName = request.pathVariable("name");
         return request.bodyToMono(Content.class)
-            .flatMap(content -> client.fetch(Post.class, postName)
+            .flatMap(content -> Mono.defer(() -> client.fetch(Post.class, postName)
                     .flatMap(post -> {
                         PostRequest postRequest = new PostRequest(post, content);
                         return postService.updatePost(postRequest);
-                })
+                    }))
+                .retryWhen(Retry.backoff(5, Duration.ofMillis(100))
+                    .filter(throwable -> throwable instanceof OptimisticLockingFailureException))
             )
             .flatMap(post -> ServerResponse.ok().bodyValue(post));
     }

application/src/main/java/run/halo/app/core/extension/endpoint/SinglePageEndpoint.java

@@ -171,11 +171,13 @@ public class SinglePageEndpoint implements CustomEndpoint {
     Mono<ServerResponse> updateContent(ServerRequest request) {
         String pageName = request.pathVariable("name");
         return request.bodyToMono(Content.class)
-            .flatMap(content -> client.fetch(SinglePage.class, pageName)
+            .flatMap(content -> Mono.defer(() -> client.fetch(SinglePage.class, pageName)
                     .flatMap(page -> {
                         SinglePageRequest pageRequest = new SinglePageRequest(page, content);
                         return singlePageService.update(pageRequest);
-                })
+                    }))
+                .retryWhen(Retry.backoff(5, Duration.ofMillis(100))
+                    .filter(throwable -> throwable instanceof OptimisticLockingFailureException))
             )
             .flatMap(post -> ServerResponse.ok().bodyValue(post));
     }