storage analyze

Author: y123456yz

mongo/src/mongo/db/repl/replication_info.cpp

@@ -196,7 +196,7 @@ class OplogInfoServerStatus : public ServerStatusSection {
         }
 
         BSONObjBuilder result;
-        // TODO(siyuan) Output term of OpTime
+        // TODO(siyuan) Output term of OpTime  
         result.append("latestOptime", replCoord->getMyLastAppliedOpTime().getTimestamp());
 
         const std::string& oplogNS =

mongo/src/mongo/db/storage/kv/kv_catalog.cpp

@@ -420,7 +420,7 @@ void KVCatalog::FeatureTracker::putInfo(OperationContext* opCtx, const FeatureBi
 
 ////KVStorageEngine::KVStorageEngine中构造初始化
 KVCatalog::KVCatalog(RecordStore* rs, bool directoryPerDb, bool directoryForIndexes)
-    : _rs(rs), //对应WiredTigerRecordStore
+    : _rs(rs), //对应WiredTigerRecordStore,对应_mdb_catalog.wt元数据文件操作
       _directoryPerDb(directoryPerDb),
       _directoryForIndexes(directoryForIndexes),
       _rand(_newRand()) {}
@@ -444,6 +444,7 @@ bool KVCatalog::_hasEntryCollidingWithRand() const {
 
 //KVCatalog::newCollection   KVCatalog::putMetaData中调用
 //_newUniqueIdent()函数获得collection对应的文件名字（ident），一个集合对应一个wt文件
+//注意，这里是生成一个唯一的ident，这里的算法值得学习
 std::string KVCatalog::_newUniqueIdent(StringData ns, const char* kind) {
     // If this changes to not put _rand at the end, _hasEntryCollidingWithRand will need fixing.
     StringBuilder buf;

mongo/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.h

@@ -54,7 +54,7 @@ class WiredTigerRecordStore;
 class WiredTigerSessionCache;
 class WiredTigerSizeStorer;
 
-//wiredtiger中的wt文件通过以下方式打开wt内容:
+//wiredtiger中的wt文件通过以下方式打开wt内容(注意wt用官方的):
 //  1. wt -C "extensions=[/usr/local/lib/libwiredtiger_snappy.so]" -h . dump table:_mdb_catalog
 //  2. ./wt -v -h /home/yangyazhou/backup2  -C "extensions=[./ext/compressors/snappy/.libs/libwiredtiger_snappy.so]"   dump  file:WiredTigerLAS.wt
 //  3. ./wt -v -h /home/yangyazhou/backup2  -C "extensions=[./ext/compressors/snappy/.libs/libwiredtiger_snappy.so]"   dump  file:WiredTiger.wt

mongo/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp

@@ -765,7 +765,7 @@ int64_t WiredTigerRecordStore::cappedMaxSize() const {
     return _cappedMaxSize;
 }
 
-//获取WiredTigerRecordStore对应表的大小
+//获取WiredTigerRecordStore对应表的磁盘空间占用大小
 int64_t WiredTigerRecordStore::storageSize(OperationContext* opCtx,
                                            BSONObjBuilder* extraInfo,
                                            int infoLevel) const {

mongo/src/mongo/db/ttl.cpp

@@ -134,6 +134,7 @@ class TTLMonitor : public BackgroundJob {
         ttlPasses.increment();
 
         // Get all TTL indexes from every collection.
+        //把拥有TTL的索引找出来
         for (const std::string& collectionNS : ttlCollections) {
             NamespaceString collectionNSS(collectionNS);
             AutoGetCollection autoGetCollection(&opCtx, collectionNSS, MODE_IS);