[Python] How to enable the round-robin load balancing policy?

[pj2]

Hi

I've looked around the GitHub project and I notice that round-robin is supported as a load balancing policy in gRPC core. Is there an option to set the policy in Python? Is there any documentation / parts of the code I can refer to?

Thanks

[pj2]

After digging around in core, I've found that this is the solution:

chan = grpc.insecure_channel("other-server.example.com", ("grpc.lb_policy_name", "round_robin"))

As a side note: it would be nice if ChannelArgKey contained lb_policy_name as a constant.

Thanks

[pj2]

Slight error: the last argument should be a list of tuples.

[Amit Saha]

On Wednesday, September 20, 2017 at 8:52:00 PM UTC+10, pj2 wrote:

Slight error: the last argument should be a list of tuples.

I have been trying to get my head around this (not yet looked deep enough). However, perhaps you would know - given that we have a single server address, how is the load balancing happening (and between what)? 

Thank you in advance.

[pj2]

Hello,

In my previous example, other-server.example.com is a DNS record which resolves to multiple IPs (each one running a gRPC server). Thus, the client will distribute requests over this channel evenly among these IPs.

Thanks

[Amit Saha]

On Sat, 7 Oct 2017 at 10:03 pm, 'pj2' via grpc.io <grp...@googlegroups.com> wrote:

Hello,

In my previous example, other-server.example.com is a DNS record which resolves to multiple IPs (each one running a gRPC server). Thus, the client will distribute requests over this channel evenly among these IPs.

I see, thank you. Do you by any chance have any reference to the code in gRPC core? Does it implement a higher level logic over the default getaddrinfo() [1] or similar on other systems?

[1] https://linux.die.net/man/3/getaddrinfo

Thanks

On Saturday, October 7, 2017 at 9:17:00 AM UTC+1, Amit Saha wrote:

On Wednesday, September 20, 2017 at 8:52:00 PM UTC+10, pj2 wrote:

Slight error: the last argument should be a list of tuples.

I have been trying to get my head around this (not yet looked deep enough). However, perhaps you would know - given that we have a single server address, how is the load balancing happening (and between what)? 

Thank you in advance.

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[pj2]

getaddrinfo is used in src/core/lib/iomgr/resolve_address_posix.cc.

The results of getaddrinfo is used by the DNS resolver (component which takes your target string and converts it into a list of addresses) at src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc.

Some relevant documentation may be found here:

• https://github.com/grpc/grpc/blob/master/doc/naming.md#detailed-design
  
• https://github.com/grpc/grpc/blob/master/doc/load-balancing.md#workflow
  

[Amit Saha]

Great, thank you.

 

• 
  

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[stefan lei]

What's "other-server.example.com " ?  some grpc server ?