FDB needs a way exclude certain role

apple / foundationdb

FoundationDB - the open source, distributed, transactional key-value store

https://apple.github.io/foundationdb/

Apache License 2.0

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FDB needs a way exclude certain role #1501

Open kaomakino opened 5 years ago

kaomakino commented 5 years ago

Today, fdbserver can be either 1. any role or 2. one specific role. When we want to run the entire cluster on a single machine (e.g. developer's laptop), it is very hard to create many processes of one specific role, because each process requires a good amount of memory. However, if we run the multiple roles in one process, it is extremely hard to properly profile for a certain role. We need a way to exclude a certain role here. For example:

[fdbserver.4500]
class = everything but not storage
[fdbserver.4501]
class = storage

This way, we can easily profile only the storage server. This is not only useful for profiling, but also debugging sometime.

alexmiller-apple commented 5 years ago

Recruitment will stop after the first process class that can hold a role. So if you have 5 processes with stateless, 1 process with proxy, and you ask for 3 proxies, you'll get 1 proxy. This solves the problem for everything that's not storage, as storage is recruited differently.

The "everything but not storage" role you're looking for is called transaction, as in, "anything in the transaction subsystem". Running one transaction process and one storage process will leave you with one storage server and one everything-else server.

kaomakino commented 5 years ago

That's super! Many thanks for the tip, Alex! So, this will solve the problem with storage. But what if I want to profile a TLog? I think we still want to have some flexibility here.

alexmiller-apple commented 5 years ago