ipc size between kdb+ servers

[bigdata-dan]

Hi,

How large is the messaging overheard in kdb+?
Is there a specification of messaging format?
Can I tell what size sending a table requires?

Thanks.

[Ryan Hamilton]

The messaging overhead in kdb+ is minimal. Few bytes for a header describing type/format is usually all and messages can be compressed.

The protocol is specified here:
http://code.kx.com/wiki/Reference/ipcprotocol

Serialization examples

serializing an integer of value 1

`
q)-8!1
0x010000000d000000fa01000000
`
We can break this down as

0x01 – architecture used for encoding the message, big endian (0) or little endian (1)
00 – message type (0 – async, 1 – sync, 2 – response)
0000
0d000000 – msg length (13)
fa – type of element following (-6, meaning a 4 byte integer follows)
01000000 – the 4 byte int value (1)

IPC of int vector

`q)-8!enlist 1
0x010000001200000006000100000001000000
`
0x01 – little endian
000000
12000000 – message length
06 – type (int vector)
00 – attributes (00 – none, 01 – s, 02 – u, 03 – p, 04 – g)
01000000 – vector length (1)
01000000 – the element, a 4 byte integer (1)

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