[dpdk-dev] [PATCH v5 00/13] introduce telemetry library

[Laatz, Kevin]

Hi Mattias,

Thanks for the input and clarification. I will include these changes in 
the v6.

Regards,
Kevin

On 22/10/2018 08:11, Mattias Rönnblom wrote:
> On 2018-10-19 12:16, Laatz, Kevin wrote:
>> On 03/10/2018 20:06, Mattias Rönnblom wrote:
>>> On 2018-10-03 19:36, Kevin Laatz wrote:
>>>> From: Ciara Power <ciara.power at intel.com>
>>>> +
>>>> +    if (!telemetry->request_client) {
>>>> +        TELEMETRY_LOG_ERR("No client has been chosen to write to");
>>>> +        return -1;
>>>> +    } > +
>>>> +    if (!json_string) {
>>>> +        TELEMETRY_LOG_ERR("Invalid JSON string!");
>>>> +        return -1;
>>>> +    }
>>>> +
>>>> +    ret = send(telemetry->request_client->fd,
>>>> +            json_string, strlen(json_string), 0);
>>>
>>> How would this code handle a partial success (as in, for example, 
>>> half of the string fits the socket buffer)? In not, maybe switching 
>>> over to a SOCK_SEQPACKET AF_UNIX socket would be the best way around 
>>> it.
>>>
>> Is the suggestion here simply to use socket(AF_UNIX, SOCK_SEQPACKET) 
>> instead of (AF_UNIX, SOCK_STREAM) ?
>
> That would be the most straight-forward to the problem, I think. 
> Linux' SOCK_SEQPACKET implementation has problems with really large 
> messages (since a per-message linear buffer is allocated), but I'm 
> guessing these messages are not in the hundreds-of-kb range.
>
>>>
>>>> +
>>>> +    buffer_read = read(telemetry->accept_fd, buf, BUF_SIZE-1);
>>>
>>> This and the below code seem to assume that read() returns one and 
>>> only one message, but on a SOCK_STREAM, there is no such thing as a 
>>> message. It's a byte stream, and you need to provide your own 
>>> framing, or have an application protocol which allows only have one 
>>> outstanding request. If you do the latter, you still need to allow 
>>> for "short" (partial) read()s (i.e. re-read() until done).
>>>
>> Will the above solve this part of the problem too?
>>
>
> Yes. The kernel will delivered the application (at most) one message, 
> in its entirety.