无法创建超过 500 兆字节的上限集合 [英] Cannot create a capped collection larger than 500 Megabytes

问题描述

我在 32 位系统上使用 Mongo db，我需要创建一个最大大小为 1GB 的大型上限集合.在 64 位系统上一切正常，但在 32 位系统上出现错误:

I'm using a Mongo db on 32bit system and I need to create a large capped collection with a max size of 1GB. Everything works fine on 64bit system, but on 32bit I'm getting the error:

com.mongodb.CommandResult$CommandFailure: command failed [command failed [create] { 
"serverUsed" : "localhost:27017" , 
"errmsg" : "exception: assertion db\\pdfile.cpp:437" , 
"code" : 0 , 
"ok" : 0.0}

在 32 位系统上，服务器的总存储大小为 2GB，但即使有这个大小，我也无法创建大于 500MB 的集合.这个神奇的数字是什么意思?

The total storage size for the server is 2GB on 32bit system, but even with this size I can't create a collection larger than 500MB. What does this magic number mean?

Mongo db 服务器版本为 2.0.6

Mongo db server version is 2.0.6

附加信息:

我有几个数据库文件，总大小为 34MB.在运行 mongo db 之前，我将这些文件复制到data"目录中，启动 Mongo db，然后在 shell 中我看到总大小相同的数字 - 35651584 (34MB)(命令使用的是从下面的评论中获取的).如果我尝试创建一个大小为 500MB 的集合，我会看到添加了一个新文件 (512MB).但是，例如，如果我尝试创建一个大小为 600MB 的集合，则会出现上面描述的错误(但仍添加了 512MB 的文件).

I have a couple of database files, the total size of which is 34MB. Before running a mongo db, I'm copying those files into the 'data' directory, starting Mongo db and then in shell I see the same number for the totat size - 35651584 (34MB) (the command used is taken from the comments below). If I try to create a collection of size 500MB I see a new file added (512MB). But if for example I will try to create a collection of size 600MB, I have an error discribed above (but the 512MB file still added).

Mongo db 服务器日志

Mongo db 使用命令行选项启动:

The Mongo db is started with the command line options:

> db.adminCommand("getCmdLineOpts")
{
        "argv" : [
                "mongod.exe",
                "--dbpath",
                "..\\data",
                "-vvvvvv",
                "--logpath",
                "..\\log\\server.log"
        ],
        "parsed" : {
                "dbpath" : "..\\data",
                "logpath" : "..\\log\\server.log",
                "vvvvvv" : true
        },
        "ok" : 1
}
>

推荐答案

MongoDB 运行在 64 位系统上好多了，你能改成 x64 吗?正如 Stennie 所说，由于数据库中的其他数据，您很可能会达到 mmap 限制.

MongoDB runs much better on a 64-bit system, can you change to x64? As Stennie said you're must likely hitting a mmap limit due to other data in your database.

您能否通过连接 mongo shell 并尝试通过运行一个比 512 MB 大 1 个字节的新集合来创建一个新集合来测试这个假设 -

Can you test this hypothesis by connecting with the mongo shell and trying to create a new by running a new collection that is 1 byte larger than 512 MB -

db.createCollection("mycoll6", {capped:true, size:536870913})

您应该会收到以下错误消息 -

You should hopefully get the following error message -

"errmsg" : "exception: can't map file memory - mongo requires 64 bit build for larger datasets",

在 Mongo shell 中，连接到 admin 数据库，查看你的数据库大小，看看你有多少数据 -

In the Mongo shell, connect to the admin database and view the size of your database to see how much data you have -

use admin
show dbs

更新:基于一些额外的测试(我使用的是 Ubuntu 12.04 32 位)，这似乎是一个错误.

Update: based on some additional testing (I used Ubuntu 12.04 32-bit), this seems like it could be a bug.

Ubuntu 测试

db.createCollection("my13", {ipped:true, size:536608768}){"errmsg" : "异常:断言 db/pdfile.cpp:437",代码":0，好的":0}db.createCollection("my13", {capped:true, size:536608767}){ "ok" : 1 }`

db.createCollection("my13", {capped:true, size:536608768}) { "errmsg" : "exception: assertion db/pdfile.cpp:437", "code" : 0, "ok" : 0 } db.createCollection("my13", {capped:true, size:536608767}) { "ok" : 1 }`

536608767 字节略低于 512 MB，为文件中的某种标题留出空间.

536608767 bytes is a little under 512 MB, leaving room for some sort of header in the file.

我认为这可能与 [smallfiles][2] 相关，因为所有 32 位安装都使用该选项运行，但是，带有 smallfiles 的 x64 构建确实如此没有表现出相同的症状.

I thought it was maybe related to [smallfiles][2] as all 32-bit installs run with that option, however, an x64 build with the smallfiles does not display the same symptoms.

我已针对此问题记录了 SERVER-6722.

I have logged SERVER-6722 for this issue.

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