报错
mongod -dbpath=/Users/zhangxi/Documents/study/mall/server/db
2018-12-03T21:59:21.622+0800 I CONTROL [main] Automatically disabling TLS 1.0, to force-enable TLS 1.0 specify --sslDisabledProtocols 'none'
2018-12-03T21:59:21.644+0800 I CONTROL [initandlisten] MongoDB starting : pid=3659 port=27017 dbpath=/Users/zhangxi/Documents/study/mall/server/db 64-bit host=zhangxideMacBook-Air.local
2018-12-03T21:59:21.644+0800 I CONTROL [initandlisten] db version v4.0.3
2018-12-03T21:59:21.645+0800 I CONTROL [initandlisten] git version: 7ea530946fa7880364d88c8d8b6026bbc9ffa48c
2018-12-03T21:59:21.645+0800 I CONTROL [initandlisten] allocator: system
2018-12-03T21:59:21.645+0800 I CONTROL [initandlisten] modules: none
2018-12-03T21:59:21.645+0800 I CONTROL [initandlisten] build environment:
2018-12-03T21:59:21.645+0800 I CONTROL [initandlisten] distarch: x86_64
2018-12-03T21:59:21.645+0800 I CONTROL [initandlisten] target_arch: x86_64
2018-12-03T21:59:21.645+0800 I CONTROL [initandlisten] options: { storage: { dbPath: "/Users/zhangxi/Documents/study/mall/server/db" } }
2018-12-03T21:59:21.649+0800 I STORAGE [initandlisten] Detected data files in /Users/zhangxi/Documents/study/mall/server/db created by the 'wiredTiger' storage engine, so setting the active storage engine to 'wiredTiger'.
2018-12-03T21:59:21.649+0800 I STORAGE [initandlisten] wiredtiger_open config: create,cache_size=3584M,session_max=20000,eviction=(threads_min=4,threads_max=4),config_base=false,statistics=(fast),log=(enabled=true,archive=true,path=journal,compressor=snappy),file_manager=(close_idle_time=100000),statistics_log=(wait=0),verbose=(recovery_progress),
2018-12-03T21:59:22.258+0800 E STORAGE [initandlisten] WiredTiger error (-31802) [1543845562:258346][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 588: unable to read root page from file:WiredTiger.wt: WT_ERROR: non-specific WiredTiger error Raw: [1543845562:258346][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 588: unable to read root page from file:WiredTiger.wt: WT_ERROR: non-specific WiredTiger error
2018-12-03T21:59:22.258+0800 E STORAGE [initandlisten] WiredTiger error (0) [1543845562:258404][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 595: WiredTiger has failed to open its metadata Raw: [1543845562:258404][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 595: WiredTiger has failed to open its metadata
2018-12-03T21:59:22.258+0800 E STORAGE [initandlisten] WiredTiger error (0) [1543845562:258419][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 598: This may be due to the database files being encrypted, being from an older version or due to corruption on disk Raw: [1543845562:258419][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 598: This may be due to the database files being encrypted, being from an older version or due to corruption on disk
2018-12-03T21:59:22.258+0800 E STORAGE [initandlisten] WiredTiger error (0) [1543845562:258502][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 601: You should confirm that you have opened the database with the correct options including all encryption and compression options Raw: [1543845562:258502][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 601: You should confirm that you have opened the database with the correct options including all encryption and compression options
2018-12-03T21:59:22.285+0800 E STORAGE [initandlisten] WiredTiger error (-31802) [1543845562:285957][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 588: unable to read root page from file:WiredTiger.wt: WT_ERROR: non-specific WiredTiger error Raw: [1543845562:285957][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 588: unable to read root page from file:WiredTiger.wt: WT_ERROR: non-specific WiredTiger error
2018-12-03T21:59:22.286+0800 E STORAGE [initandlisten] WiredTiger error (0) [1543845562:286013][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 595: WiredTiger has failed to open its metadata Raw: [1543845562:286013][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 595: WiredTiger has failed to open its metadata
2018-12-03T21:59:22.286+0800 E STORAGE [initandlisten] WiredTiger error (0) [1543845562:286052][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 598: This may be due to the database files being encrypted, being from an older version or due to corruption on disk Raw: [1543845562:286052][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 598: This may be due to the database files being encrypted, being from an older version or due to corruption on disk
2018-12-03T21:59:22.286+0800 E STORAGE [initandlisten] WiredTiger error (0) [1543845562:286172][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 601: You should confirm that you have opened the database with the correct options including all encryption and compression options Raw: [1543845562:286172][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 601: You should confirm that you have opened the database with the correct options including all encryption and compression options
2018-12-03T21:59:22.294+0800 E STORAGE [initandlisten] WiredTiger error (-31802) [1543845562:294147][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 588: unable to read root page from file:WiredTiger.wt: WT_ERROR: non-specific WiredTiger error Raw: [1543845562:294147][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 588: unable to read root page from file:WiredTiger.wt: WT_ERROR: non-specific WiredTiger error
2018-12-03T21:59:22.294+0800 E STORAGE [initandlisten] WiredTiger error (0) [1543845562:294213][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 595: WiredTiger has failed to open its metadata Raw: [1543845562:294213][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 595: WiredTiger has failed to open its metadata
2018-12-03T21:59:22.294+0800 E STORAGE [initandlisten] WiredTiger error (0) [1543845562:294240][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 598: This may be due to the database files being encrypted, being from an older version or due to corruption on disk Raw: [1543845562:294240][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 598: This may be due to the database files being encrypted, being from an older version or due to corruption on disk
2018-12-03T21:59:22.294+0800 E STORAGE [initandlisten] WiredTiger error (0) [1543845562:294298][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 601: You should confirm that you have opened the database with the correct options including all encryption and compression options Raw: [1543845562:294298][3659:0x11fee35c0], file:WiredTiger.wt, connection: __wt_btree_tree_open, 601: You should confirm that you have opened the database with the correct options including all encryption and compression options
2018-12-03T21:59:22.300+0800 W STORAGE [initandlisten] Failed to start up WiredTiger under any compatibility version.
2018-12-03T21:59:22.300+0800 W STORAGE [initandlisten] WiredTiger metadata corruption detected
2018-12-03T21:59:22.316+0800 F STORAGE [initandlisten] Please read the documentation for starting MongoDB with --repair here: http://dochub.mongodb.org/core/repair
2018-12-03T21:59:22.316+0800 F - [initandlisten] Fatal Assertion 50944 at src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp 628
2018-12-03T21:59:22.317+0800 F - [initandlisten]
***aborting after fassert() failure
原因：
关机时，mongodb忘记关闭，导致mongodb无法重新启动，查看log文件，发现了如下error log
也就是意外推出时数据被锁定了，登陆mongo给的推荐链接找到了解决办法：
1.删除锁文件，这个锁文件位于你存储data数据的目录
rm /db/mongod.lock
2.修复数据文件
mongod --dbpath /db --repair
3.重启mongo
mongod --dbpath /db