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From Noble Paul <>
Subject Re: SolrCloud is sick.
Date Sat, 02 Nov 2019 23:31:54 GMT

I believe there is a consensus on what is wrong with the way we have built
the cluster state and overseer. We need to focus a bit more on the design
aspect. Design, according to me, has the following elements:

* How does it work?

* What are the performance characteristics? Can it be done more efficiently?

* What are the public touch points?

** Which are the files we store in ZK? Are they expected to be watched

** Or are they read on demand?

** The public APIs. Does it make sense to the user? Can it be further
simplified? How does it compare to the other APIs in the system?

We, as a community, do a bad job in dealing with these. While we focus on
internal things, these are not discussed before it is too late. We usually
do coding, tests, code review (sometimes) and commit. This leads to huge
technical debt.

This is not to put blame on one person or a group of people. (I
occasionally see people discussing design issues upfront, I just hope that
is the norm.)

Now, why am I discussing this in this thread?

While we agree there are problems, we are trying to solve the problem using
the same process we used to create these problems. Again, I'm not
questioning the intent or competence of anyone. Unless we set the process
right, we are doomed to make the same mistakes again.

I whole heartedly endorse any effort to improve SolrCloud/overseer. At the
same time I fail to see us leveraging the collective experience of our
community through meaningful discussion.

I hope we don't resort to personal attacks and use this as an opportunity
to improve our processes.

On Sun, Nov 3, 2019, 9:52 AM Scott Blum <> wrote:

> Very much agreed.  I've been trying to figure out for a long time what is
> the point in having a replica DOWN state that has to be toggled (DOWN and
> then UP!) every time a node restarts.  Considering that we could just
> combine ACTIVE and `live_nodes` to understand whether a replica is
> available.  It's not even foolproof since kill -9 on a solr node won't mark
> all the replicas DOWN-- that doesn't happen until the node comes back up
> (perversely).
> What would it take to get to a state where restarting a node would require
> a minimal amount of ZK work in most cases?
> On Sat, Nov 2, 2019 at 5:44 PM Mark Miller <> wrote:
>> Give me a short bit to follow up and I will lay out my case and proposal.
>> Everyone is then free to decide that we need to do something drastic or
>> that I'm wrong and we should just continue down the same road. If that's
>> the case, a lot of your work will get a lot easier and less impeded by me
>> and we will still all be happier. Win win.
>> If we can just not make drastic changes for a just a brief week or so
>> window, I'll say what I have to say, you guys can judge and do whatever
>> you'd please.
>> - mark
>> On Fri, Nov 1, 2019 at 7:46 PM Mark Miller <> wrote:
>>> Hey All Solr Dev's,
>>> SolrCloud is sick right now. The way low level Zookeeper is handeled,
>>> the Overseer, is mix and mess of proper exception handling and super slow
>>> startup and shutdown, adding new things all the time with no concern for
>>> performance or proper ordering (which is harder to tell than you think).
>>> Our class dependency graph doesn't even work - we just force it. Sort
>>> of. If the whole system  doesn't block and choke it's way to a start slow
>>> enough, lots of things fail.
>>> This thing coughs up, you toss stuff into the storm, a good chunk of
>>> time, what you want eventually come back without causing too much damage.
>>> There are so many things are are off or just plain wrong and the list is
>>> growing and growing. No one is following this or if you are, please back me
>>> up. This thing will collapse under it's own wait.
>>> So if you want to add yet another state format cluster state or some
>>> other optimization on this junk heap, you can expect me to push back.
>>> We should all be embarrassed by the state of things.
>>> I've got some ideas for addressing them that I'll share soon, but god,
>>> don't keep optimizing a turd in non backcompat Overseer loving ways. That
>>> Overseer is an atrocity.
>>> --
>>> - Mark
>> --
>> - Mark

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