Re: Question about communication between mysqld and ndbd

[Lukas Pecha]

Well, those machines are not at one location, they are separated by a
few kilometers. There is only 100Mbps connection between them, gigabit
is not possible. They are also on different subnets. But I need to have
two applications to share the same database data and to have
simultanneous read/write access, so I thought, that since the database
shouldn't grow bigger than a few megabytes (about twenty megs, I think,
and most of the tables have only tens of rows, few hundreds max) in the
future, that this connection will suffice. Link is stable and round trip
time is about 7 ms. MySQL cluster also helps me to achieve the high
availability goal - database will still be up even if one location
completely burns out.

Here are my configuration files for cluster and mysqld: (Maybe I should
lower the numbers of allocated memory, I just picked them randomly)
And, I have to add - I have also two management nodes, running on the
same two nodes as ndbd and mysqld. Everything seems to run smoothly, it
even passed some "tearing off the cable/power supply" tests. It just has
such a long query responses.

Thanks again in advance for any advice

Lukas Pecha

-----------------config.ini------------
[ndbd default]
NoOfReplicas=2
DataMemory=512M
IndexMemory=192M

[tcp default]
portnumber=2202 
[ndb_mgmd]
Id=1
ArbitrationRank=0
hostname=192.168.1.10
datadir=/mysql-mgm
[ndb_mgmd]
Id=2
ArbitrationRank=0
hostname=192.168.1.140
datadir=/mysql-mgm
# SQL node options:
[ndbd]
Id=3
DataDir=/mysql-data
HostName=192.168.1.10
BackupDataDir=/mysql-backup
HeartbeatIntervalDbDb=8000
HeartbeatIntervalDbApi=8000
[ndbd]
Id=4
DataDir=/mysql-data
HostName=192.168.1.140
BackupDataDir=/mysql-backup
HeartbeatIntervalDbDb=8000
HeartbeatIntervalDbApi=8000
[mysqld]
Id=5
ArbitrationRank=0
HostName=192.168.1.10
[mysqld]
Id=6
ArbitrationRank=0
HostName=192.168.1.140

----------------my.cnf-------------
[mysqld]
ndbcluster
ndb-connectstring="192.168.1.10;192.168.1.140"
default-table-type=NDBCLUSTER
[mysql_cluster]
ndb-connectstring="192.168.1.10;192.168.1.140"

Jeff Sturm napsal(a):
> Lukas,
>
> 15 seconds is a substantial performance hit.  I don't have a direct
> answer to your question, but I wonder how these two machines are
> networked--do they share a subnet?  Are you using a 1Gbps Ethernet?
>
> With only two machines, I would also experiment with a crossover cable.
>
>   
>> -----Original Message-----
>> From: Lukas Pecha [mailto:pecha@stripped]
>> Sent: Friday, June 26, 2009 7:35 AM
>> To: cluster@stripped
>> Subject: Question about communication between mysqld and ndbd
>>
>> Hi,
>> I set up a small mysql-cluster configuration with two ndbd/API
>>     
> machines
>   
>> - so there is ndbd and mysqld running on both of them. But I am not
>>     
> able to find a
>   
>> way how to change a way the mysqld process communicates with ndbd - it
>>     
> seems,
>   
>> that the machines are sending request to remote ndbd (not local), so
>>     
> even not much
>   
>> complex queries take a long time (one simple query with "order by"
>>     
> statement takes
>   
>> about 15 second and the table has only about twenty thousand rows).
>>     
> When I kill one
>   
>> of the ndbd processes, the query takes only 0,2 sec on the machine
>>     
> with both ndbd
>   
>> and mysqld running and still 15 seconds on the other machine. When I
>>     
> start it up again,
>   
>> both machines have again the response time about 15 seconds.
>>
>> So my question is - is there a way, how to tell mysqld, that it should
>>     
> use only local ndb
>   
>> daemon for querying? Or will this issue be resolved, if I start using
>>     
> indexing
>   
>> everywhere I could?
>>
>> Thanks in advance
>> Lukas Pecha
>>     
>
>
>
>