## Background ### etcd grpc
In previous versions, apisix used HTTP to connect with etcd's grpc-gateway. But it had the following disadvantages: 1. Each admin resource per worker process, e.g. routes, needs to use a dedicated TCP connection, i.e. each worker process will have more than 10 TCP connections, which increases the load on the etcd server. 2. Some extra features only exist in etcd server, not in grpc-gateway. 3. etcd official may remove grpc-gateway at some date. So we introduce grpc here to replace http. However this module has too many bugs, meanwhile, we will introduce a new conf server (maybe it's etcd-adapter) later, which will act as a real etcd server but supports different db backends, e..g postgresql. So we plan to remove etcd grpc in apisix. On the other hand, HTTP optimizations have been merged into the apisix master branch: 1. fix(etcd): reuse cli and enable keepalive https://github.com/apache/apisix/pull/9420 2. feat(config_etcd): use a single long http connection to watch all resources https://github.com/apache/apisix/pull/9456 After optimization, the HTTP way is as good as the grpc way. ### current conf server This is an internal feature added earlier and is intended to be database backend agnostic. However, the current implementation is a simple pure proxy between DP/CP and etcd. Also, this makes debugging via gdb difficult, since all handlers downstream and upstream will always be triggered. It also obscures configuration. It's worth noting that the decoupled mode doesn't work currently. Since we'll be using the new unified external config server later, we'd rather remove the currently useless dumb version. And after refactoring, all deploy modes will work fine. ### github bug issues https://github.com/apache/apisix/issues/9381 https://github.com/apache/apisix/issues/9347 https://github.com/apache/apisix/issues/8067 https://github.com/apache/apisix/issues/9212 https://github.com/apache/apisix/issues/9007 https://github.com/apache/apisix/issues/9336 https://github.com/apache/apisix/issues/9049 https://github.com/apache/apisix/issues/9582 https://github.com/apache/apisix/issues/9578 https://github.com/apache/apisix/issues/9528 ## Conculsion All in all, we wish to revert the apisix etcd access to 2.x behavior, i.e. connect etcd directly via HTTP, but that doesn't mean we lose grpc and config db variants, instead we will implement a separate conf server to provide these features.
