Re: [dpdk-stable] [PATCH v4 1/1] fbarray: get fbarrays from containerized secondary

[Yasufumi Ogawa <yasufum.o@gmail.com>]

Hi David,

Thank you for your comments.

On 2019/10/26 0:36, David Marchand wrote:
> On Fri, Oct 11, 2019 at 11:36 AM David Marchand
> <david.marchand@redhat.com> wrote:
>>
>> Some comments.
> 
> ping.
> 
> 
>>
>> The title does not reflect the observed issue.
I would like to consider to revise it.

>> I understand that secondary processeses can't be started from a docker
>> container.
I've confirmed that secondary process can be started as a container app 
with SPP, and DPDK v18.08 and v19.08. SPP is a multi-process app 
supporting container usecases.
http://git.dpdk.org/apps/spp/

>> The patch title should reflect this.
>>
>> On Wed, Jul 24, 2019 at 10:20 AM <yasufum.o@gmail.com> wrote:
>>>
>>> From: Yasufumi Ogawa <ogawa.yasufumi@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 because hostname is assigned as a short form of 64
>>> digits full container ID in docker.
>>>
>>> Cc: stable@dpdk.org
>>
>> I don't think we want to backport this behavior change.
This issue was included from DPDK v18.08, and some users of SPP are 
still using stable 18.11. So, I would appreciate if you agree to backport.

>>
>>>
>>> Signed-off-by: Yasufumi Ogawa <ogawa.yasufumi@lab.ntt.co.jp>
>>> ---
>>>   lib/librte_eal/linux/eal/eal_memalloc.c | 28 +++++++++++++++++++++++--
>>>   1 file changed, 26 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/lib/librte_eal/linux/eal/eal_memalloc.c b/lib/librte_eal/linux/eal/eal_memalloc.c
>>> index 1f6a7c18f..356b304a8 100644
>>> --- a/lib/librte_eal/linux/eal/eal_memalloc.c
>>> +++ b/lib/librte_eal/linux/eal/eal_memalloc.c
>>> @@ -1366,6 +1366,7 @@ secondary_msl_create_walk(const struct rte_memseg_list *msl,
>>>          struct rte_memseg_list *primary_msl, *local_msl;
>>>          char name[PATH_MAX];
>>>          int msl_idx, ret;
>>> +       char proc_id[33] = { 0 };  /* 32bytes is enough if using hostname */
>>
>> This variable only makes sense in the if (getpid() == 1) branch,
>> please move it there, and see below comment about using gethostname().
Sure. It works correctly in secondary app container and I should replace it.

>>
>>>
>>>          if (msl->external)
>>>                  return 0;
>>> @@ -1375,8 +1376,31 @@ secondary_msl_create_walk(const struct rte_memseg_list *msl,
>>>          local_msl = &local_memsegs[msl_idx];
>>>
>>>          /* create distinct fbarrays for each secondary */
>>> -       snprintf(name, RTE_FBARRAY_NAME_LEN, "%s_%i",
>>> -               primary_msl->memseg_arr.name, getpid());
>>> +       /* If run secondary in a container, the name of fbarray file should
>>> +        * not be decided with pid because getpid() always returns 1.
>>> +        * In docker, hostname is assigned as a short form of full container
>>> +        * ID. So use hostname as unique ID among containers instead.
>>
>> I understand this is how it works for docker.
>> Is this the same in other container environments?
Umm... I've tested on other than docker because I don't have test 
environment. I am not sure which of container runtimes should be 
supported actually. I think it is enough as the first step to fix this 
issue of docker. Moreover, the essential problem is that getpid() 
returns 1 in docker or not.

I am also not sure which of environments other than docker should be 
supported if necessary. What do you think?

>>
>>
>>> +        */
>>> +       if (getpid() == 1) {
>>> +               FILE *hn_fp;
>>> +               hn_fp = fopen("/etc/hostname", "r");
>>
>> Why not use gethostname() ?
>> Plus, this api defines the maximum size of the hostname as HOST_NAME_MAX bytes.
Yes. I should use gethostname() and replace hardcoded size with 
HOST_NAME_MAX.

Thanks,
Yasufumi

>>
>>> +               if (hn_fp == NULL) {
>>> +                       RTE_LOG(ERR, EAL,
>>> +                               "Cannot open '/etc/hostname' for secondary\n");
>>> +                       return -1;
>>> +               }
>>> +
>>> +               /* with docker, /etc/hostname just has one entry of hostname */
>>> +               if (fscanf(hn_fp, "%32s", proc_id) == EOF) {
>>> +                       fclose(hn_fp);
>>> +                       return -1;
>>> +               }
>>> +               fclose(hn_fp);
>>> +       } else
>>> +               sprintf(proc_id, "%d", (int)getpid());
>>> +
>>> +       snprintf(name, RTE_FBARRAY_NAME_LEN, "%s_%s",
>>> +                       primary_msl->memseg_arr.name, proc_id);
>>>
>>>          ret = rte_fbarray_init(&local_msl->memseg_arr, name,
>>>                  primary_msl->memseg_arr.len,
> 
>