Would cqlsh describe command send query to cassandra server ?

[陈仕（shichen）-技术产品中心 <sh...@qiyi.com>]

Hello, all.

I try to use `desc keyspaces` or desc table t`, and at the same time capture network packets at Cassandra side with tcpdump.
My tcpdump command is like this: tcpdump -i eth0 ip host 10.110.27.6 -X
But I found no string such as desc or keyspaces or table in the output.

So I wonder whether cqlsh fetch keyspace’s and table’s metadata just from local and not send query to server node ?

Thanks.

答复: [营销类邮件] Re: Would cqlsh describe command send query to cassandra server ?

[陈仕（shichen）-技术产品中心 <sh...@qiyi.com>]

Thanks for replying. That's to say, the drivers fetch metadata from server with heartbeat interval 30s. Right ?

So if I change the value of one property of a table, I can see the change at cqlsh commandline within at most 30s ?


-----邮件原件-----
发件人: Benjamin Lerer [mailto:benjamin.lerer@datastax.com] 
发送时间: 2018年8月7日 19:45
收件人: dev@cassandra.apache.org
主题: [营销类邮件] Re: Would cqlsh describe command send query to cassandra server ?

Hi,

DESCRIBE commands are handled at the driver level not at the server level.
The drivers fetch metadata and keep them up to date.
When a DESCRIBE command is send, the driver build the output from those metadata.

Benjamin

On Tue, Aug 7, 2018 at 1:33 PM, 陈仕（shichen）-技术产品中心 <sh...@qiyi.com> wrote:

>
> Hello, all.
>
> I try to use `desc keyspaces` or desc table t`, and at the same time 
> capture network packets at Cassandra side with tcpdump.
> My tcpdump command is like this: tcpdump -i eth0 ip host 10.110.27.6 
> -X But I found no string such as desc or keyspaces or table in the output.
>
> So I wonder whether cqlsh fetch keyspace’s and table’s metadata just 
> from local and not send query to server node ?
>
> Thanks.
>

Re: Would cqlsh describe command send query to cassandra server ?

[Benjamin Lerer <be...@datastax.com>]

Hi,

DESCRIBE commands are handled at the driver level not at the server level.
The drivers fetch metadata and keep them up to date.
When a DESCRIBE command is send, the driver build the output from those
metadata.

Benjamin

On Tue, Aug 7, 2018 at 1:33 PM, 陈仕（shichen）-技术产品中心 <sh...@qiyi.com> wrote:

>
> Hello, all.
>
> I try to use `desc keyspaces` or desc table t`, and at the same time
> capture network packets at Cassandra side with tcpdump.
> My tcpdump command is like this: tcpdump -i eth0 ip host 10.110.27.6 -X
> But I found no string such as desc or keyspaces or table in the output.
>
> So I wonder whether cqlsh fetch keyspace’s and table’s metadata just from
> local and not send query to server node ?
>
> Thanks.
>