add comment cache

2019-06-19 13:07:41 +08:00
parent 4a1527a982
commit e97c939831
3 changed files with 139 additions and 9 deletions
--- a/src/cache.js
+++ b/src/cache.js
@@ -0,0 +1,98 @@
+const CACHE_DB_VER=1;
+const MAINTENANCE_STEP=500;
+const MAINTENANCE_COUNT=5000;
+
+class Cache {
+    constructor() {
+        this.db=null;
+        this.added_items_since_maintenance=0;
+        const open_req=indexedDB.open('hole_cache_db',CACHE_DB_VER);
+        open_req.onerror=console.error.bind(console);
+        open_req.onupgradeneeded=(event)=>{
+            console.log('comment cache db upgrade');
+            const db=event.target.result;
+            const store=db.createObjectStore('comment',{
+                keyPath: 'pid',
+            });
+            store.createIndex('last_access','last_access',{unique: false});
+        };
+        open_req.onsuccess=(event)=>{
+            console.log('comment cache db loaded');
+            this.db=event.target.result;
+            setTimeout(this.maintenance.bind(this),1);
+        };
+    }
+
+    get(pid,target_version) {
+        return new Promise((resolve,reject)=>{
+            if(!this.db)
+                return resolve(null);
+            const tx=this.db.transaction(['comment'],'readwrite');
+            const store=tx.objectStore('comment');
+            const get_req=store.get(pid);
+            get_req.onsuccess=()=>{
+                let res=get_req.result;
+                if(!res)  {
+                    console.log('cache miss');
+                    resolve(null);
+                } else if(target_version===res.version) { // hit
+                    console.log('cache hit');
+                    res.last_access=+new Date();
+                    store.put(res);
+                    resolve(res.data);
+                } else { // expired
+                    console.log('cache expired: ver',res.version,'target',target_version);
+                    store.delete(pid);
+                    resolve(null);
+                }
+            };
+            get_req.onerror=reject;
+        });
+    }
+
+    put(pid,target_version,data) {
+        return new Promise((resolve,reject)=>{
+            if(!this.db)
+                return resolve();
+            const tx=this.db.transaction(['comment'],'readwrite');
+            const store=tx.objectStore('comment');
+            store.put({
+                pid: pid,
+                version: target_version,
+                data: data,
+                last_access: +new Date(),
+            });
+            if(++this.added_items_since_maintenance===MAINTENANCE_STEP)
+                setTimeout(this.maintenance.bind(this),1);
+        });
+    }
+
+    maintenance() {
+        if(!this.db)
+            return;
+        const tx=this.db.transaction(['comment'],'readwrite');
+        const store=tx.objectStore('comment');
+        let count_req=store.count();
+        count_req.onsuccess=()=>{
+            let count=count_req.result;
+            if(count>MAINTENANCE_COUNT) {
+                console.log('comment cache db maintenance',count);
+                store.index('last_access').openKeyCursor().onsuccess=(e)=>{
+                    let cur=e.target.result;
+                    if(cur) {
+                        console.log('maintenance: delete',cur);
+                        store.delete(cur.primaryKey);
+                        if(--count>MAINTENANCE_COUNT)
+                            cur.continue();
+                    }
+                };
+            } else {
+                console.log('comment cache db not full',count);
+            }
+            this.added_items_since_maintenance=0;
+        };
+        count_req.onerror=console.error.bind(console);
+    }
+};
+
+export let cache=new Cache();