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I am trying to run some of my micro services within consul service mesh. As per consul documentation, it is clear that consul takes care of routing, load balancing and service discovery. But their documentation also talks about 3rd party load balancers like NGINX, HAProxy and F5.
https://learn.hashicorp.com/collections/consul/load-balancing
If consul takes care of load balancing, then what is the purpose of these load balancers.
My assumptions,
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These load balancers are to replace the built-in load balancing technique of consul, but the LB still uses consul service discovery data. (Why anyone need this !!!)
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Consul only provides load balancing for east-west traffic (within the service mesh). To load balance north-south traffic (internet traffic), we need external load balancers.
Please let me know which of my assumption is correct
2
Answers
I checked with one of my colleagues (full disclosure: I work for F5) and he mentioned that whereas it is not a technical requirement to use external services for load balancing, a lot of organizations already have the infrastructure in place, along with the operational requirements, policies, and procedures that come with it.
For some examples on how Consul might work with edge services like the F5 BIG-IP, here are a couple articles you might find interesting that can provide context for your question.
F5, Terraform, and Consul
Consul service mesh uses Envoy proxy by default for both east-west and north-south load balancing of connections within the mesh. Whereas east-west traffic is routed through a sidecar proxy, north-south connections route through an instance of Envoy which is configured to act as an ingress gateway.
In addition to Consul’s native, Envoy ingress, Consul also supports integrations with other proxies and API gateways. These can be used if you require functionality which is not available in the native ingress offering.
Third party proxies leverage Consul’s service catalog to populate their backend/upstream member pools with endpoint information from Consul. This allows the proxy to always have an up-to-date list of healthy and available services in the data center, and eliminates the need to manually reconfigure the north-south proxy when adding/removing service endpoints.
Some gateways like Ambassador, F5, and (soon) Traefik (see PR https://github.com/traefik/traefik/pull/7407) go a step further by integrating with the service mesh (see Connect custom proxy integration) so that they can utilize mTLS when connecting to backend services.