As far as I understand - embedded zookeeper is for intended
single-node SolrClouds.
I run a containerized solrcloud and use `docker run --network host`
for zookeeper and solr startup on three dedicated hosts.
On Mon, Jul 21, 2025 at 10:08 AM Uwe Reh <r...@rz.uni-frankfurt.de> wrote:
>
> Dear experts,
>
> I hope you could help.
>
> *My question in brief*
> Is it possible to disable the usage of ZooKeeper's dynamic
> reconfiguration? Or is there another way to solve the problem described
> below?
>
> *Situation*
> We are using SOLR in single-server mode for years. However, the time has
> finally come to migrate to SolrCloud.
> Our constraints are:
> - Kubernetes(SolrOperator) is not an option.
> - All ZooKeeper and Solr nodes must run as containers.
>
> After digging through documentation and doing some research, I was able
> to configure a fully containerized solution that is up and running.
> (Solr 9.8.1, ZK 3.9.3)
> However, there is still an annoying flaw.
>
> *Components of the flaw*
> * Running a containerized SolrCloud with embedded ZooKeepers seems to be
> impossible.
> * An external ZooKeeper ensemble requires an initial list of nodes
> ("host_1:ports, host_2:ports, host_3:ports"). To run a node as container
> it's crucial to configure 0.0.0.0 instead of the host's IP address. For
> example, a ZooKeeper container running on host_2 needs the list
> "host_1:ports, 0.0.0.0:ports, host_3:ports".
> * It appears that Solr utilizes 'zkHosts' only at startup. In order to
> take advantage of ZooKeeper's dynamic reconfiguration Solr seems to
> prefer the list fetched from the ZooKeeper ensemble.
>
>
> *Annoying result*
> Even though It is possible to run a fully containerized SolrCloud. The
> GUI '/solr/#/~cloud?view=zkstatus' reports: "Failed talking to
> Zookeeper 0.0.0.0:2181"
> The 0.0.0.0 in a ZooKeeper container isn't visible for a Solr container.
> For this, each Solr node can only see n-1 ZooKeeper nodes.
>
> This issue is known for years:
> https://stackoverflow.com/questions/64351894/solr-cloud-cannot-connect-to-random-zookeeper-node-full-docker-set-up
> I can't believe that no one has found a workaround or solution yet.
> - Perhaps there is a hidden flag for Solr to preserve the given
> 'zkHosts'. (Ignore Zookeeper's dynamic reconfiguration)?
> - Or maybe there's a hidden flag for ZooKeeper to start up with 0.0.0.0
> even if there is a different IP is configured for this node (myid)?
> * ???
>
> Any help is appreciated
> Uwe
