Re: [grpc-io] gRPC client fallback from load-balancer to round robin DNS endpoint on LB outage

[Krishna Sai Veera Reddy]

Will take a look. Thank you Larry and Terry! Much appreciated!

On Monday, November 6, 2023 at 4:10:09 PM UTC-8 Terry Wilson wrote:

> Krishna,
>
> I'll mention that we also have a short guide on custom LBs 
>  that can help you 
> with the fundamentals.
>
> On Monday, November 6, 2023 at 3:53:01 PM UTC-8 Larry Safran wrote:
>
>> Yes, you will need a custom NameResolver.  
>> You could have your NameResolver do one of the following
>> 1)  Extend DnsNameResolver (as is done by the internal GrpcNameResolver) 
>> and override the doResolve method
>> 2)  Directly extend NameResolver and have a field with a DnsNameResolver 
>> created through the DnsNameResolverProvider (which should be gotten from 
>> the registry).  
>>
>> There is already a load balancer that is switching between 2 child load 
>> balancers.  It is experimental and can be specified as 
>> "priority_experimental".  What it does is to use a specific attribute that 
>> must be set by the NameResolver.  Even if you go with your own load 
>> balancer, that would be the best way to differentiate which addresses 
>> should be used for which child.  If you want to use it as an example, it is 
>> https://github.com/grpc/grpc-java/blob/master/xds/src/main/java/io/grpc/xds/PriorityLoadBalancer.java
>>
>>
>>
>> On Mon, Nov 6, 2023 at 1:53 PM Krishna Sai Veera Reddy <
>> krishnasaiv...@gmail.com> wrote:
>>
>>> Hey Larry,
>>>
>>> Thank you for your response! Are there any examples out in the wild on 
>>> how to do this? Also the part that is confusing me is the name resolution. 
>>> Do we have to add a custom name resolution policy as well so that we get 
>>> both the LB and round robin IP addresses in `acceptResolvedAddresses 
>>> `
>>>  
>>> method in the LB policy?
>>>
>>> On Friday, November 3, 2023 at 12:50:20 PM UTC-7 Larry Safran wrote:
>>>
 This is a perfect scenario for a custom LB policy.  Since LB policies 
 form a tree, you could easily have your policy delegate to either a 
 PickFirst or RoundRobin policy depending on whether or not the LB is up.  
 Just have your policy define a ForwardingLoadbalanceHelper whose 
 updateBalancingState passes the picker from the oppropriate downstream 
 policy.

 On Fri, Nov 3, 2023 at 12:29 PM Krishna Sai Veera Reddy <
 krishnasaiv...@gmail.com> wrote:

> Hello All,
>
> I am working on a gRPC client that connects to a gRPC service fronted 
> by an LB but would like the client to automatically fallback to using 
> round-robin DNS to directly connect to the backend servers when the LB 
> goes 
> down. How do I go about this? Would I need to implement my own custom LB 
> policy? Any help is appreciated and thanks in advance!
>
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>  
> 
> .
>
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>>>  
>>> 
>>> .
>>>
>>

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Re: [grpc-io] gRPC client fallback from load-balancer to round robin DNS endpoint on LB outage

['Terry Wilson' via grpc.io]

Krishna,

I'll mention that we also have a short guide on custom LBs 
 that can help you with 
the fundamentals.

On Monday, November 6, 2023 at 3:53:01 PM UTC-8 Larry Safran wrote:

> Yes, you will need a custom NameResolver.  
> You could have your NameResolver do one of the following
> 1)  Extend DnsNameResolver (as is done by the internal GrpcNameResolver) 
> and override the doResolve method
> 2)  Directly extend NameResolver and have a field with a DnsNameResolver 
> created through the DnsNameResolverProvider (which should be gotten from 
> the registry).  
>
> There is already a load balancer that is switching between 2 child load 
> balancers.  It is experimental and can be specified as 
> "priority_experimental".  What it does is to use a specific attribute that 
> must be set by the NameResolver.  Even if you go with your own load 
> balancer, that would be the best way to differentiate which addresses 
> should be used for which child.  If you want to use it as an example, it is 
> https://github.com/grpc/grpc-java/blob/master/xds/src/main/java/io/grpc/xds/PriorityLoadBalancer.java
>
>
>
> On Mon, Nov 6, 2023 at 1:53 PM Krishna Sai Veera Reddy <
> krishnasaiv...@gmail.com> wrote:
>
>> Hey Larry,
>>
>> Thank you for your response! Are there any examples out in the wild on 
>> how to do this? Also the part that is confusing me is the name resolution. 
>> Do we have to add a custom name resolution policy as well so that we get 
>> both the LB and round robin IP addresses in `acceptResolvedAddresses 
>> `
>>  
>> method in the LB policy?
>>
>> On Friday, November 3, 2023 at 12:50:20 PM UTC-7 Larry Safran wrote:
>>
>>> This is a perfect scenario for a custom LB policy.  Since LB policies 
>>> form a tree, you could easily have your policy delegate to either a 
>>> PickFirst or RoundRobin policy depending on whether or not the LB is up.  
>>> Just have your policy define a ForwardingLoadbalanceHelper whose 
>>> updateBalancingState passes the picker from the oppropriate downstream 
>>> policy.
>>>
>>> On Fri, Nov 3, 2023 at 12:29 PM Krishna Sai Veera Reddy <
>>> krishnasaiv...@gmail.com> wrote:
>>>
 Hello All,

 I am working on a gRPC client that connects to a gRPC service fronted 
 by an LB but would like the client to automatically fallback to using 
 round-robin DNS to directly connect to the backend servers when the LB 
 goes 
 down. How do I go about this? Would I need to implement my own custom LB 
 policy? Any help is appreciated and thanks in advance!

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 https://groups.google.com/d/msgid/grpc-io/df8f4a85-5020-4c68-bb94-cbea67d7c75an%40googlegroups.com
  
 
 .

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> To view this discussion on the web visit 
>> https://groups.google.com/d/msgid/grpc-io/2e7b95aa-cd66-40f5-bf41-0484fa12892cn%40googlegroups.com
>>  
>> 
>> .
>>
>

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Re: [grpc-io] gRPC client fallback from load-balancer to round robin DNS endpoint on LB outage

['Larry Safran' via grpc.io]

Yes, you will need a custom NameResolver.
You could have your NameResolver do one of the following
1)  Extend DnsNameResolver (as is done by the internal GrpcNameResolver)
and override the doResolve method
2)  Directly extend NameResolver and have a field with a DnsNameResolver
created through the DnsNameResolverProvider (which should be gotten from
the registry).

There is already a load balancer that is switching between 2 child load
balancers.  It is experimental and can be specified as
"priority_experimental".  What it does is to use a specific attribute that
must be set by the NameResolver.  Even if you go with your own load
balancer, that would be the best way to differentiate which addresses
should be used for which child.  If you want to use it as an example, it is
https://github.com/grpc/grpc-java/blob/master/xds/src/main/java/io/grpc/xds/PriorityLoadBalancer.java



On Mon, Nov 6, 2023 at 1:53 PM Krishna Sai Veera Reddy <
krishnasaiveerareddy...@gmail.com> wrote:

> Hey Larry,
>
> Thank you for your response! Are there any examples out in the wild on how
> to do this? Also the part that is confusing me is the name resolution. Do
> we have to add a custom name resolution policy as well so that we get both
> the LB and round robin IP addresses in `acceptResolvedAddresses
> `
> method in the LB policy?
>
> On Friday, November 3, 2023 at 12:50:20 PM UTC-7 Larry Safran wrote:
>
>> This is a perfect scenario for a custom LB policy.  Since LB policies
>> form a tree, you could easily have your policy delegate to either a
>> PickFirst or RoundRobin policy depending on whether or not the LB is up.
>> Just have your policy define a ForwardingLoadbalanceHelper whose
>> updateBalancingState passes the picker from the oppropriate downstream
>> policy.
>>
>> On Fri, Nov 3, 2023 at 12:29 PM Krishna Sai Veera Reddy <
>> krishnasaiv...@gmail.com> wrote:
>>
>>> Hello All,
>>>
>>> I am working on a gRPC client that connects to a gRPC service fronted by
>>> an LB but would like the client to automatically fallback to using
>>> round-robin DNS to directly connect to the backend servers when the LB goes
>>> down. How do I go about this? Would I need to implement my own custom LB
>>> policy? Any help is appreciated and thanks in advance!
>>>
>>> --
>>> You received this message because you are subscribed to the Google
>>> Groups "grpc.io" group.
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>>> an email to grpc-io+u...@googlegroups.com.
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>>> https://groups.google.com/d/msgid/grpc-io/df8f4a85-5020-4c68-bb94-cbea67d7c75an%40googlegroups.com
>>> 
>>> .
>>>
>> --
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> 
> .
>

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Re: [grpc-io] gRPC client fallback from load-balancer to round robin DNS endpoint on LB outage

[Krishna Sai Veera Reddy]

Hey Larry,

Thank you for your response! Are there any examples out in the wild on how 
to do this? Also the part that is confusing me is the name resolution. Do 
we have to add a custom name resolution policy as well so that we get both 
the LB and round robin IP addresses in `acceptResolvedAddresses 
`
 
method in the LB policy?

On Friday, November 3, 2023 at 12:50:20 PM UTC-7 Larry Safran wrote:

> This is a perfect scenario for a custom LB policy.  Since LB policies form 
> a tree, you could easily have your policy delegate to either a PickFirst or 
> RoundRobin policy depending on whether or not the LB is up.  Just have your 
> policy define a ForwardingLoadbalanceHelper whose updateBalancingState 
> passes the picker from the oppropriate downstream policy.
>
> On Fri, Nov 3, 2023 at 12:29 PM Krishna Sai Veera Reddy <
> krishnasaiv...@gmail.com> wrote:
>
>> Hello All,
>>
>> I am working on a gRPC client that connects to a gRPC service fronted by 
>> an LB but would like the client to automatically fallback to using 
>> round-robin DNS to directly connect to the backend servers when the LB goes 
>> down. How do I go about this? Would I need to implement my own custom LB 
>> policy? Any help is appreciated and thanks in advance!
>>
>> -- 
>> You received this message because you are subscribed to the Google Groups 
>> "grpc.io" group.
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>> email to grpc-io+u...@googlegroups.com.
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>> https://groups.google.com/d/msgid/grpc-io/df8f4a85-5020-4c68-bb94-cbea67d7c75an%40googlegroups.com
>>  
>> 
>> .
>>
>

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Re: [grpc-io] gRPC client fallback from load-balancer to round robin DNS endpoint on LB outage

['Larry Safran' via grpc.io]

This is a perfect scenario for a custom LB policy.  Since LB policies form
a tree, you could easily have your policy delegate to either a PickFirst or
RoundRobin policy depending on whether or not the LB is up.  Just have your
policy define a ForwardingLoadbalanceHelper whose updateBalancingState
passes the picker from the oppropriate downstream policy.

On Fri, Nov 3, 2023 at 12:29 PM Krishna Sai Veera Reddy <
krishnasaiveerareddy...@gmail.com> wrote:

> Hello All,
>
> I am working on a gRPC client that connects to a gRPC service fronted by
> an LB but would like the client to automatically fallback to using
> round-robin DNS to directly connect to the backend servers when the LB goes
> down. How do I go about this? Would I need to implement my own custom LB
> policy? Any help is appreciated and thanks in advance!
>
> --
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> grpc.io" group.
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> 
> .
>

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[grpc-io] gRPC client fallback from load-balancer to round robin DNS endpoint on LB outage

[Krishna Sai Veera Reddy]

Hello All,

I am working on a gRPC client that connects to a gRPC service fronted by an 
LB but would like the client to automatically fallback to using round-robin 
DNS to directly connect to the backend servers when the LB goes down. How 
do I go about this? Would I need to implement my own custom LB policy? Any 
help is appreciated and thanks in advance!

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