Cassandra数据库淹没了？ [英] Cassandra Database overwhelmed?
问题描述
我使用以下查询在cassandra数据库中创建了一个表：
I created a table in a cassandra database with the following query:
CREATE TABLE table(
num int,
part_key int,
val1 int,
val2 float,
val3 text,
...,
PRIMARY KEY((part_key),num)
);
表存储来自技术设备的数据。分区键part_key对于每个记录为1，因为我想只在一个服务器上执行范围查询。我知道这是Cassandra的一个坏的用例，但我需要做这个比较。
The table stores data from a technical device. The partitioning key part_key is 1 for the every record, because I want to execute range queries on only one server. I know this is a bad use case for Cassandra, but I need to do this for a comparison.
主键num是记录的编号（从1到
The primary key num is the number of the record (from 1 to 8.000.000).
每个记录有四百个其他值，分别是float，int和text类型。 I在此表中插入8.000.000条记录（43 GB），并想要运行我的查询：
There are like 400 other values per record that are float, int and text type. I Inserted 8.000.000 records to this table (43 GB) and wanted to run my queries like:
SELECT num, val1, val45, val90
FROM ks.table
WHERE part_key=1 AND num>9999 AND num<20001;
我在cql-shell中执行查询并得到操作超时。因此，我将cassandra.yaml文件中的read_request_timeout_in_ms和range_request_timeout_in_ms更改为60000（2分钟）。
I executed the query in the cql-shell and got "operation timed out". So I changed read_request_timeout_in_ms and range_request_timeout_in_ms in the cassandra.yaml file to 60000 (2 minutes).
再次执行查询时出现错误10054：由remotehost5分钟后。 Datastax Cassandra社区服务器2.0.11服务在服务器上不再运行。
When executing the query again I got "Error 10054: the existing connection was closed by the remotehost" after 5 minutes. The Datastax Cassandra Community Server 2.0.11 Service was not running anymore on the server.
我重新启动了服务，再次尝试，服务再次崩溃。我甚至不能重新启动服务，我不得不重新启动服务器。
我也尝试过使用Cassandra cpp驱动程序，也无法执行此查询。
I restarted the service, tried it again and the service crashed again. I could not even restart the service and I had to restart the server. I also tried this using the Cassandra cpp-driver and also could not execute this query.
小查询，例如
... AND num<1000;
。
是：我做错了什么吗？我知道Cassandra是更好的与更多的节点，但我认为Cassandra只需要一些更多的时间。是否可能，Cassandra无法执行这样的查询？
My question is: did I do something wrong? I know Cassandra is better with more nodes but I thought that Cassandra would only need some more time. Is it possible, that Cassandra is unable to execute a query like that?
谢谢！
服务器：
Intel（R）Xeon（R）CPU E5504 @ 2.00GHz 2.00GHz（2颗处理器）/ 16GB RAM
Intel(R) Xeon(R) CPU E5504 @ 2.00GHz 2.00GHz (2 processors) / 16GB RAM
CPU利用率：50％ - 60％，15秒后约30％/ RAM：2.9 GB整个时间
CPU utilization: 50% - 60% and after 15 seconds around 30% / RAM: 2,9 GB the whole time
编辑：
我的Cassandra键空间现在是60GB和小型查询
My Cassandra keyspace is now 60GB and small queries like
... AND num<10;
，甚至插入返回超时。有时服务崩溃...
请有人知道一个想法解释了吗？一个回答说，43GB的节点在具有更多节点的集群中与在仅具有一个节点的集群中不同。有人可以解释这个吗？
and even the Inserts return time out. Sometimes the service crashes... Please can someone who got an idea explain that? One answer said that a node with 43GB is not the same in a cluster with more nodes as in my cluster with only one node. Can somebody explain this?
谢谢！
推荐答案
这里的关键问题是cqlsh与您正在运行的C *版本不通过结果页面。这意味着整个结果集必须在查询时序列化，给定您的数据模型将非常大（如kha指出）。我将尝试使用启用分页的驱动程序执行类似的查询，当然确保您有足够的网络带宽用于返回数据。
One of the key issues here is that cqlsh with the version of C* that you are running does not page through results. This means the entire result-set has to be serialized at the time of the query which given your data model will be quite large(as pointed out by kha). I would try performing similar queries using a paging enabled driver and of course make sure that you have sufficient network bandwith for returning the data.
43GB应该可以通过单个C *节点轻松处理，虽然只使用单个节点运行C *集群几乎牺牲了C *提供的所有优点。
43GB Should be easily handled by a single C* node, although operating a C* cluster with only a single node sacrifices almost all of the benefits that C* offers.
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