From 47c57220609a4695c1cd813f574a30f83cd92240 Mon Sep 17 00:00:00 2001
From: Dragory <2606411+Dragory@users.noreply.github.com>
Date: Fri, 22 May 2020 20:35:15 +0300
Subject: [PATCH] Add a shared lock for Persist and ReactionRoles plugins to
 prevent race conditions

---
 backend/src/plugins/Persist.ts       | 9 ++++++++-
 backend/src/plugins/ReactionRoles.ts | 8 ++++++--
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/backend/src/plugins/Persist.ts b/backend/src/plugins/Persist.ts
index 0232601e..ba9250eb 100644
--- a/backend/src/plugins/Persist.ts
+++ b/backend/src/plugins/Persist.ts
@@ -71,8 +71,13 @@ export class PersistPlugin extends ZeppelinPlugin<TConfigSchema> {
 
   @d.event("guildMemberAdd")
   async onGuildMemberAdd(_, member: Member) {
+    const memberRolesLock = await this.locks.acquire(`member-roles-${member.id}`);
+
     const persistedData = await this.persistedData.find(member.id);
-    if (!persistedData) return;
+    if (!persistedData) {
+      memberRolesLock.unlock();
+      return;
+    }
 
     const toRestore: MemberOptions = {};
     const config = this.getConfig();
@@ -101,5 +106,7 @@ export class PersistPlugin extends ZeppelinPlugin<TConfigSchema> {
         restoredData: restoredData.join(", "),
       });
     }
+
+    memberRolesLock.unlock();
   }
 }
diff --git a/backend/src/plugins/ReactionRoles.ts b/backend/src/plugins/ReactionRoles.ts
index 4f48ca9a..67baeae3 100644
--- a/backend/src/plugins/ReactionRoles.ts
+++ b/backend/src/plugins/ReactionRoles.ts
@@ -189,6 +189,10 @@ export class ReactionRolesPlugin extends ZeppelinPlugin<TConfigSchema> {
         timeout: null,
         changes: [],
         applyFn: async () => {
+          this.pendingRoleChanges.delete(memberId);
+
+          const lock = await this.locks.acquire(`member-roles-${memberId}`);
+
           const member = await this.getMember(memberId);
           if (member) {
             const newRoleIds = new Set(member.roles);
@@ -206,9 +210,9 @@ export class ReactionRolesPlugin extends ZeppelinPlugin<TConfigSchema> {
                 `Failed to apply role changes to ${member.username}#${member.discriminator} (${member.id}): ${e.message}`,
               );
             }
-
-            this.pendingRoleChanges.delete(memberId);
           }
+
+          lock.unlock();
         },
       };