[dpdk-stable] [dpdk-dev] [PATCH v2 1/1] fbarray: get fbarrays from containerized secondary

[Burakov, Anatoly]

On 09-Jul-19 11:24 AM, Burakov, Anatoly wrote:
> On 09-Jul-19 11:22 AM, Yasufumi Ogawa wrote:
>> Hi Anatoly,
>>
>> On 2019/07/05 17:53, Burakov, Anatoly wrote:
>>> On 16-Apr-19 4:43 AM, ogawa.yasufumi at lab.ntt.co.jp wrote:
>>>> From: Yasufumi Ogawa <ogawa.yasufumi at lab.ntt.co.jp>
>>>>
>>>> In secondary_msl_create_walk(), it creates a file for fbarrays with its
>>>> PID for reserving unique name among secondary processes. However, it
>>>> does not work if secondary is run as app container because each of
>>>> containerized secondary has PID 1. To reserve unique name, use hostname
>>>> instead of PID if the value is 1.
>>>>
>>>> Cc: stable at dpdk.org
>>>>
>>>> Signed-off-by: Yasufumi Ogawa <ogawa.yasufumi at lab.ntt.co.jp>
>>>> ---
>>>
>>> I'm not too well versed in containers - is this hostname 1) always 
>>> set, and 2) always unique?
>> For docker, 1) hostname is always set. 2) The hostname is decided as 
>> short form of container ID, so it might not be unique even though very 
>> low possibility.
>>
>> I found that we can get whole container ID in `/proc/self/cgroup` as 
>> discussed [1]. I think using hostname is reasonable way without 
>> running many secondary processes. However, it might be better to use 
>> 64 digits full container ID instead of 12 digits short ID if ensure 
>> uniqueness strongly. What do yo think?
>>
>> [1] 
>> https://forums.docker.com/t/get-a-containers-full-id-from-inside-of-itself/37237 
>>
> 
> I think it's better to err on the side of caution and guarantee better 
> uniqueness. This code will get into an LTS and will be used for years to 
> come :)
> 

...however, i think a full 64-digit ID won't even fit into the fbarray 
filename, as i believe it's limited to something like 64 chars. Perhaps 
hostname would be enough after all... or we can increase fbarray name 
length - that would require ABI breakage but the ABI is already broken 
in this release, so it's OK i think.

-- 
Thanks,
Anatoly