Re: [grpc-io] Flush dnsmasq cache on IP address failure

[Frédéric Martinsons]

Yes, as you tell, if an upstream server have the entry in cache, this will
not renew anything until the next ttl expiration.

Le lun. 17 juil. 2023, 19:49, 'apo...@google.com' via grpc.io <
grpc-io@googlegroups.com> a écrit :

> I agree that this seems outside of the scope of the grpc library.
>
> But +1 that you could in theory use a custom name resolver to implement
> some behavior like this.
>
> Also +1 that the --clear-on-reload plus SIGHUP option may be useful here.
>
> I'm curious though: suppose you can flush the local DNS cache, can you
> guarantee that there are no more caches upstream?
> On Wednesday, July 12, 2023 at 10:38:27 AM UTC-7 Richard Belleville wrote:
>
>>
>> Depending on which language you're using, you could use the custom name
>> resolver interface 
>> to implement this behavior yourself.
>> On Wednesday, July 5, 2023 at 12:53:43 PM UTC-7 Gmail wrote:
>>
>>> Thanks Frederic
>>> I understand that. But I only want to do it when grpc has a connection
>>> failure. Is there an already existing mechanism to do that.?
>>>
>>> On Jul 5, 2023, at 12:37 PM, Frédéric Martinsons 
>>> wrote:
>>>
>>> 
>>>
>>> I think this is totally unrelated to grpc but for what it worth, if you
>>> control your dnsmasq, you can use --clear-on-reload option and send a
>>> SIGHUP to dnsmasq process to reload the cache.
>>>
>>> Le mer. 5 juil. 2023, 21:24, Ramanujam Jagannath  a
>>> écrit :
>>>
 Backgrounder - Our device connects to an AWS static IP. We use dnsmasq
 on device to provide lookup services for downstream devices. Currently we
 are planning to use a long. DNS TTL on AWS to avoid too many DNS lookups
 from on field devices. The on-field devices use a grpc  connection to
 maintain long standing tcp connections. We do have multiple availability
 zones and so a DNS resolution does return 4 IP addresses

 Problem - When an IP address fails(on AWS) the grpc client will retry
 and re-resolve. But because we have dnsmasq on device it will send a cached
 address - which is potentially faulty.

 Solution - This can be resolved by flushing the dnsmasq cache on
 device. But is there a way to flush the dnsmasq cache on device on
 connection failure only? grpc under the hood uses c-ares which in our case
 goes to the dnsmasq proxy on device.

 Any solutions/thoughts. Someone must have encountered this problem
 before?

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Re: [grpc-io] Flush dnsmasq cache on IP address failure

['apo...@google.com' via grpc.io]

I agree that this seems outside of the scope of the grpc library.

But +1 that you could in theory use a custom name resolver to implement 
some behavior like this.

Also +1 that the --clear-on-reload plus SIGHUP option may be useful here.

I'm curious though: suppose you can flush the local DNS cache, can you 
guarantee that there are no more caches upstream?
On Wednesday, July 12, 2023 at 10:38:27 AM UTC-7 Richard Belleville wrote:

>
> Depending on which language you're using, you could use the custom name 
> resolver interface  
> to implement this behavior yourself.
> On Wednesday, July 5, 2023 at 12:53:43 PM UTC-7 Gmail wrote:
>
>> Thanks Frederic
>> I understand that. But I only want to do it when grpc has a connection 
>> failure. Is there an already existing mechanism to do that.?
>>
>> On Jul 5, 2023, at 12:37 PM, Frédéric Martinsons  
>> wrote:
>>
>> 
>>
>> I think this is totally unrelated to grpc but for what it worth, if you 
>> control your dnsmasq, you can use --clear-on-reload option and send a 
>> SIGHUP to dnsmasq process to reload the cache. 
>>
>> Le mer. 5 juil. 2023, 21:24, Ramanujam Jagannath  a 
>> écrit :
>>
>>> Backgrounder - Our device connects to an AWS static IP. We use dnsmasq 
>>> on device to provide lookup services for downstream devices. Currently we 
>>> are planning to use a long. DNS TTL on AWS to avoid too many DNS lookups 
>>> from on field devices. The on-field devices use a grpc  connection to 
>>> maintain long standing tcp connections. We do have multiple availability 
>>> zones and so a DNS resolution does return 4 IP addresses
>>>
>>> Problem - When an IP address fails(on AWS) the grpc client will retry 
>>> and re-resolve. But because we have dnsmasq on device it will send a cached 
>>> address - which is potentially faulty. 
>>>
>>> Solution - This can be resolved by flushing the dnsmasq cache on device. 
>>> But is there a way to flush the dnsmasq cache on device on connection 
>>> failure only? grpc under the hood uses c-ares which in our case goes to the 
>>> dnsmasq proxy on device.
>>>
>>> Any solutions/thoughts. Someone must have encountered this problem 
>>> before?
>>>
>>> -- 
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>>> Groups "grpc.io" group.
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>>>  
>>> 
>>> .
>>>
>>

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Re: [grpc-io] Flush dnsmasq cache on IP address failure

['Richard Belleville' via grpc.io]

Depending on which language you're using, you could use the custom name 
resolver interface  to 
implement this behavior yourself.
On Wednesday, July 5, 2023 at 12:53:43 PM UTC-7 Gmail wrote:

> Thanks Frederic
> I understand that. But I only want to do it when grpc has a connection 
> failure. Is there an already existing mechanism to do that.?
>
> On Jul 5, 2023, at 12:37 PM, Frédéric Martinsons  
> wrote:
>
> 
>
> I think this is totally unrelated to grpc but for what it worth, if you 
> control your dnsmasq, you can use --clear-on-reload option and send a 
> SIGHUP to dnsmasq process to reload the cache. 
>
> Le mer. 5 juil. 2023, 21:24, Ramanujam Jagannath  a 
> écrit :
>
>> Backgrounder - Our device connects to an AWS static IP. We use dnsmasq on 
>> device to provide lookup services for downstream devices. Currently we are 
>> planning to use a long. DNS TTL on AWS to avoid too many DNS lookups from 
>> on field devices. The on-field devices use a grpc  connection to maintain 
>> long standing tcp connections. We do have multiple availability zones and 
>> so a DNS resolution does return 4 IP addresses
>>
>> Problem - When an IP address fails(on AWS) the grpc client will retry and 
>> re-resolve. But because we have dnsmasq on device it will send a cached 
>> address - which is potentially faulty. 
>>
>> Solution - This can be resolved by flushing the dnsmasq cache on device. 
>> But is there a way to flush the dnsmasq cache on device on connection 
>> failure only? grpc under the hood uses c-ares which in our case goes to the 
>> dnsmasq proxy on device.
>>
>> Any solutions/thoughts. Someone must have encountered this problem before?
>>
>> -- 
>> You received this message because you are subscribed to the Google Groups 
>> "grpc.io" group.
>> To unsubscribe from this group and stop receiving emails from it, send an 
>> email to grpc-io+u...@googlegroups.com.
>> To view this discussion on the web visit 
>> https://groups.google.com/d/msgid/grpc-io/75d68762-eb58-4400-b8e1-3584f6bd6e51n%40googlegroups.com
>>  
>> 
>> .
>>
>

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Re: [grpc-io] Flush dnsmasq cache on IP address failure

[Gmail]

Thanks FredericI understand that. But I only want to do it when grpc has a connection failure. Is there an already existing mechanism to do that.?On Jul 5, 2023, at 12:37 PM, Frédéric Martinsons  wrote:I think this is totally unrelated to grpc but for what it worth, if you control your dnsmasq, you can use --clear-on-reload option and send a SIGHUP to dnsmasq process to reload the cache. Le mer. 5 juil. 2023, 21:24, Ramanujam Jagannath  a écrit :Backgrounder - Our device connects to an AWS static IP. We use dnsmasq on device to provide lookup services for downstream devices. Currently we are planning to use a long. DNS TTL on AWS to avoid too many DNS lookups from on field devices. The on-field devices use a grpc  connection to maintain long standing tcp connections. We do have multiple availability zones and so a DNS resolution does return 4 IP addressesProblem - When an IP address fails(on AWS) the grpc client will retry and re-resolve. But because we have dnsmasq on device it will send a cached address - which is potentially faulty. Solution - This can be resolved by flushing the dnsmasq cache on device. But is there a way to flush the dnsmasq cache on device on connection failure only? grpc under the hood uses c-ares which in our case goes to the dnsmasq proxy on device.Any solutions/thoughts. Someone must have encountered this problem before?



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Re: [grpc-io] Flush dnsmasq cache on IP address failure

[Frédéric Martinsons]

I think this is totally unrelated to grpc but for what it worth, if you
control your dnsmasq, you can use --clear-on-reload option and send a
SIGHUP to dnsmasq process to reload the cache.

Le mer. 5 juil. 2023, 21:24, Ramanujam Jagannath  a
écrit :

> Backgrounder - Our device connects to an AWS static IP. We use dnsmasq on
> device to provide lookup services for downstream devices. Currently we are
> planning to use a long. DNS TTL on AWS to avoid too many DNS lookups from
> on field devices. The on-field devices use a grpc  connection to maintain
> long standing tcp connections. We do have multiple availability zones and
> so a DNS resolution does return 4 IP addresses
>
> Problem - When an IP address fails(on AWS) the grpc client will retry and
> re-resolve. But because we have dnsmasq on device it will send a cached
> address - which is potentially faulty.
>
> Solution - This can be resolved by flushing the dnsmasq cache on device.
> But is there a way to flush the dnsmasq cache on device on connection
> failure only? grpc under the hood uses c-ares which in our case goes to the
> dnsmasq proxy on device.
>
> Any solutions/thoughts. Someone must have encountered this problem before?
>
> --
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> 
> .
>

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