Reduce long-running federation transactions

Stop wrapping remote federation post persistence in explicit
transactions in inbox handlers and remote actor post imports.
This avoids holding database transactions open while fetching
remote ActivityPub objects, preview cards, and media
attachments, which should reduce PostgreSQL INSERT waiting
pile-ups when remote servers are slow or unresponsive.

Document the change in the 0.7.9 changelog.

Refs #411

Author: dahlia

CHANGES.md

@@ -6,6 +6,16 @@ Version 0.7.9
 
 To be released.
 
+ -  Reduced the risk of long-running PostgreSQL transactions during federation
+    processing.  Federation inbox handlers and remote actor post imports no
+    longer wrap remote post/account persistence in explicit transactions, which
+    could otherwise stay open while fetching remote ActivityPub objects,
+    preview cards, and media attachments.  This should reduce `INSERT waiting`
+    pile-ups and improve resilience when remote servers are slow or
+    unresponsive.  [[#411]]
+
+[#411]: https://github.com/fedify-dev/hollo/issues/411
+
 
 Version 0.7.8
 -------------

src/federation/account.ts

@@ -246,16 +246,14 @@ export async function persistAccountPosts(
       } else if (activity instanceof Announce) {
         const item = await activity.getObject(options);
         if (!isPost(item)) continue;
-        await db.transaction(async (tx) => {
-          const post = await persistSharingPost(tx, activity, item, baseUrl, {
-            ...options,
-            account,
-          });
-          if (post?.sharingId != null) {
-            await updatePostStats(tx, { id: post.sharingId });
-          }
-          if (post != null) i++;
+        const post = await persistSharingPost(db, activity, item, baseUrl, {
+          ...options,
+          account,
         });
+        if (post?.sharingId != null) {
+          await updatePostStats(db, { id: post.sharingId });
+        }
+        if (post != null) i++;
       }
       if (i >= fetchPosts) break;
     }

src/federation/inbox.ts

@@ -424,13 +424,12 @@ export async function onPostCreated(
 ): Promise<void> {
   const object = await create.getObject();
   if (!isPost(object)) return;
-  const post = await db.transaction(async (tx) => {
-    const post = await persistPost(tx, object, ctx.origin, ctx);
-    if (post?.replyTargetId != null) {
-      await updatePostStats(tx, { id: post.replyTargetId });
-    }
-    return post;
-  });
+  // Avoid wrapping persistPost() in an explicit transaction.
+  // It may fetch remote ActivityPub objects, preview cards, and media files.
+  const post = await persistPost(db, object, ctx.origin, ctx);
+  if (post?.replyTargetId != null) {
+    await updatePostStats(db, { id: post.replyTargetId });
+  }
 
   // Create status notification for reply target author (if this is a reply)
   // and mention notifications for other mentioned local users
@@ -586,19 +585,10 @@ export async function onPostShared(
 ): Promise<void> {
   const object = await announce.getObject();
   if (!isPost(object)) return;
-  const post = await db.transaction(async (tx) => {
-    const post = await persistSharingPost(
-      tx,
-      announce,
-      object,
-      ctx.origin,
-      ctx,
-    );
-    if (post?.sharingId != null) {
-      await updatePostStats(tx, { id: post.sharingId });
-    }
-    return post;
-  });
+  const post = await persistSharingPost(db, announce, object, ctx.origin, ctx);
+  if (post?.sharingId != null) {
+    await updatePostStats(db, { id: post.sharingId });
+  }
   if (post?.sharing?.account?.owner != null) {
     await ctx.forwardActivity(
       { username: post.sharing.account.owner.handle },
@@ -669,16 +659,14 @@ export async function onPostPinned(
   const accountList = await db.query.accounts.findMany({
     where: eq(accounts.featuredUrl, add.targetId.href),
   });
-  await db.transaction(async (tx) => {
-    const post = await persistPost(tx, object, ctx.origin, ctx);
-    if (post == null) return;
-    for (const account of accountList) {
-      await tx.insert(pinnedPosts).values({
-        postId: post.id,
-        accountId: account.id,
-      } satisfies NewPinnedPost);
-    }
-  });
+  const post = await persistPost(db, object, ctx.origin, ctx);
+  if (post == null) return;
+  for (const account of accountList) {
+    await db.insert(pinnedPosts).values({
+      postId: post.id,
+      accountId: account.id,
+    } satisfies NewPinnedPost);
+  }
 }
 
 export async function onPostUnpinned(
@@ -691,20 +679,18 @@ export async function onPostUnpinned(
   const accountList = await db.query.accounts.findMany({
     where: eq(accounts.featuredUrl, remove.targetId.href),
   });
-  await db.transaction(async (tx) => {
-    const post = await persistPost(tx, object, ctx.origin, ctx);
-    if (post == null) return;
-    for (const account of accountList) {
-      await tx
-        .delete(pinnedPosts)
-        .where(
-          and(
-            eq(pinnedPosts.postId, post.id),
-            eq(pinnedPosts.accountId, account.id),
-          ),
-        );
-    }
-  });
+  const post = await persistPost(db, object, ctx.origin, ctx);
+  if (post == null) return;
+  for (const account of accountList) {
+    await db
+      .delete(pinnedPosts)
+      .where(
+        and(
+          eq(pinnedPosts.postId, post.id),
+          eq(pinnedPosts.accountId, account.id),
+        ),
+      );
+  }
 }
 
 export async function onLiked(