Make cluster_id optional

Just provide the default value — "demo".

changed milestone to %Release 0.1 - Demo

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assigned to @rosik

mentioned in commit b06ea92c

mentioned in merge request !136 (merged)

mentioned in commit 36281ce4

как насчёт генерировать uuid? здесь так советуют делать: https://www.openlife.cc/sites/default/files/4-modifications-for-Raft-consensus.pdf

Как мне кажется, там немного другие цели преследуются. Самое интересное на мой взгляд:

However, it is also allowed to call InitializeCluster on a server that is already part of an initialized
cluster (that has one or more members). This could be necessary for a number of reasons. In
the Raft algorithm itself, it is for example possible to get into a state where a majority of servers
have been lost permanently. The cluster is now without a leader and will not be able to accept
new events from clients, and also will not be able to elect a new leader. Without a leader it is
also impossible to correct the situation, since AddServer and RemoveServer should be called
on the leader.

In such cases the solution is to call InitializeCluster again, essentially starting a new cluster from
the remains of the one that was just lost. As the databaseId is now re­generated, this also helps
prevent split brain. Or, in the case that the admin would call InitializeCluster on multiple parts of
the lost cluster, they would still split into separately identifiable parts, each with their own distinct
databaseId.

А пока в имплементации raft-rs нет databaseId, нам остается только прикручивать эту проверку сбоку — в тарантульных хранимках. Но потом, не сейчас (c).

Но cluster_id закладывался с другой целью. К его появлению нас привели примерно следующие рассуждения:

1. Что делать пикодате, если пользователь по невнимательности добавит инстанс не в тот кластер, в который хотел?
2. Давайте заставим пользователя на каждом инстансе прописывать один и тот же cluster_id, так он точно не ошибется.

Последнее утверждение мне кажется наивным и ложным. Поэтому пусть cluster_id хотя бы не мешается в первом релизе.

mentioned in commit d3f3ce05

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mentioned in commit 2ea3b697

closed with merge request !136 (merged)

closed with commit 2ea3b697