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Ubuntu 运行 mongodb 的正确姿势

曾经在多个项目中使用 mongodb,但是最近从头开始安装并启动居然遇到了不少问题。在此记录一下:

环境:Ubuntu 12.04 64bit
版本:mongodb 3.0.2

首先,按照官方教程安装 mongodb。在这个教程中,注意到有一句话

The MongoDB instance stores its data files in /var/lib/mongodb and its log files in /var/log/mongodb by default, and runs using the mongodb user account. You can specify alternate log and data file directories in /etc/mongod.conf.

恩,看来意思是我们可以通过改 /etc/mongod.conf 这个配置文件来设置 data 存放路径。 打开这个文件看看,的确是有这些配置。

# Note: if you run mongodb as a non-root user (recommended) you may
# need to create and set permissions for this directory manually,
# e.g., if the parent directory isn't mutable by the mongodb user.
dbpath=/var/lib/mongodb

#where to log
logpath=/var/log/mongodb/mongod.log

这里假设要用以下命令(称为命令1)启动 mongodb ,指定 wiredTiger 作为存储引擎并标示副本集:

mongod --storageEngine wiredTiger --replSet fbt   # 称为命令1

首先我们非常天真地直接执行上面那行命令:

2015-04-23T14:55:16.152+0800 I STORAGE  [initandlisten] exception in initAndListen: 29 Data directory /data/db not found., terminating
2015-04-23T14:55:16.152+0800 I CONTROL  [initandlisten] dbexit:  rc: 100

Oops,似乎不行,说 /data/db 不存在。这里就是很坑爹的地方了:虽然 mongod.conf 指定了 dbpath,但是实际上这个配置文件没有起作用!而 mongodb 本身认为 /data/db 才是默认路径。毫无疑问,文档在这方面没有写清楚,因此也有别人被坑过。(后来发现,通过 sudo service mongod start 方式启动会默认使用该配置文件)要想让配置生效,必须手动指定配置文件路径,即:

mongod --storageEngine wiredTiger --replSet fbt -f /etc/mongod.conf

不过这里不打算用这种方式。既然没有 /data/db 这个路径,创建一个不就好了?

sudo mkdir -p /data/db

继续执行命令1,继续报错

2015-04-23T15:17:49.274+0800 E NETWORK  [initandlisten] Failed to unlink socket file /tmp/mongodb-27017.sock errno:1 Operation not permitted
2015-04-23T15:17:49.274+0800 I -        [initandlisten] Fatal Assertion 28578
2015-04-23T15:17:49.274+0800 I -        [initandlisten]

***aborting after fassert() failure

既然它删不掉 /tmp/mongodb-27017.sock,那我手动删。删完之后再次执行命令1:

2015-04-23T15:19:44.972+0800 I STORAGE  [initandlisten] exception in initAndListen: 98 Unable to create/open lock file: /data/db/mongod.lock errno:13 Permission denied Is a mongod instance already running?, terminating
2015-04-23T15:19:44.972+0800 I CONTROL  [initandlisten] dbexit:  rc: 100

这个是可以预期的权限问题,因为我们是拿 sudo 创建的 /data/db 文件夹,而执行的时候没有用 sudo。万能的 stackoverflow 告诉我们要这样做:

sudo chown -R `id -u` /data/db

执行之后当前用户就可以在 /data/db 创建文件了。再次执行命令1

fbt@ebs-39239:~/mongodb$ mongod --storageEngine wiredTiger --replSet fbt
2015-04-23T15:29:38.158+0800 I STORAGE  [initandlisten] wiredtiger_open config: create,cache_size=1G,session_max=20000,eviction=(threads_max=4),statistics=(fast),log=(enabled=true,archive=true,path=journal,compressor=snappy),checkpoint=(wait=60,log_size=2GB),statistics_log=(wait=0),
2015-04-23T15:29:38.264+0800 I CONTROL  [initandlisten] MongoDB starting : pid=30024 port=27017 dbpath=/data/db 64-bit host=ebs-39239
2015-04-23T15:29:38.265+0800 I CONTROL  [initandlisten]
2015-04-23T15:29:38.265+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2015-04-23T15:29:38.265+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2015-04-23T15:29:38.265+0800 I CONTROL  [initandlisten]
2015-04-23T15:29:38.265+0800 I CONTROL  [initandlisten] db version v3.0.2
2015-04-23T15:29:38.265+0800 I CONTROL  [initandlisten] git version: 6201872043ecbbc0a4cc169b5482dcf385fc464f
2015-04-23T15:29:38.265+0800 I CONTROL  [initandlisten] OpenSSL version: OpenSSL 1.0.1 14 Mar 2012
2015-04-23T15:29:38.265+0800 I CONTROL  [initandlisten] build info: Linux ip-10-111-179-219 3.2.0-36-virtual #57-Ubuntu SMP Tue Jan 8 22:04:49 UTC 2013 x86_64 BOOST_LIB_VERSION=1_49
2015-04-23T15:29:38.265+0800 I CONTROL  [initandlisten] allocator: tcmalloc
2015-04-23T15:29:38.265+0800 I CONTROL  [initandlisten] options: { replication: { replSet: "fbt" }, storage: { engine: "wiredTiger" } }
2015-04-23T15:29:38.334+0800 I REPL     [initandlisten] Did not find local replica set configuration document at startup;  NoMatchingDocument Did not find replica set configuration document in local.system.replset
2015-04-23T15:29:38.351+0800 I NETWORK  [initandlisten] waiting for connections on port 27017

这次终于 OK 了。

如果直接执行,最好是单独开一个 screen。如果不想开 screen,则应当加上 --fork 参数把 mongod放到后台去。我采取开 screen 的方式。退出 screen,执行 ps aux | grep mongo 观察 mongod 是否成功启动:

fbt      29783  0.0  0.0  29476  1676 ?        Ss   14:47   0:00 SCREEN -S mongodb
fbt      30042  3.7  1.7 209004 35496 pts/1    Sl+  15:31   0:00 mongod --storageEngine wiredTiger --replSet fbt
fbt      30059  0.0  0.0  11700   944 pts/0    S+   15:31   0:00 grep --color=auto mongo

可以看到,mongod 已经按照之前给的参数在运行了。

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