How to configure parse server to use an n-node mongo setup - parse-platform

Migrating to mongo is well documented but I could not find a reference/guidelines for configuring the server to work with an n-node mongo cluster.
Mlabs suggest that if using anything other than single node (aka sandbox) users should run tests to cover primary node failure.
Has anyone configured parse server on let's say a 3-node mongo? How?
Alternatively, what volume of users/requests should prompt an n-node mongo cluster set up?

use the uri you're given by the likes of mlab (mongo labs) - parse server will sort it out...

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system_auth replication in Cassandra

I'm trying to configure authentication on Cassandra. It seems like because of replication strategy that is used for system_auth, it can't replicate user credentials to all the nodes in cluster, so I end up getting Incorrect credentials on one node, and getting successful connection on another.
This is related question. The guy there says you have to make sure credentials are always on all nodes.
How to do it? The option that is offered there says you have to alter keyspace to put replication factor equal to amount of nodes in cluster, then run repair on each node. That's whole tons of work to be done if you want your cassandra to be dynamically scalable. If I add 1 node today, 1 node another day, alter keyspace replication and then keep restarting nodes manually that will end up some kind of chaos.
Hour of googling actually leaded to slightly mentioned EverywhereStrategy, but I don't see anywhere in docs it mentioned as available. How do people configure APIs to work with Cassandra authentication then, if you can't be sure that your user actually present on node, that you're specifying as contact point?
Obviously, talking about true scale, when you can change the size of cluster without doing restarts of each node.
When you enable authentication in Cassandra, then Yes you have increase the system_auth keyspace replication_factor to N(total number of nodes) and run a complete repair, but you don't need to restart the nodes after you add a new Node.
If repair is consuming more time then you optimize your repair like repair only the system_auth keyspace
nodetool repair system_auth
(or)
nodetool repair -pr system_auth
As per Cassandra a complete repair should be done regularly. For more details on repair see the below links:
http://www.datastax.com/dev/blog/repair-in-cassandra
https://www.pythian.com/blog/effective-anti-entropy-repair-cassandra/
http://docs.datastax.com/en/archived/cassandra/2.2/cassandra/tools/toolsRepair.html
Answering your questions:
Question: How do people configure APIs to work with Cassandra authentication then, if you can't be sure that your user actually present on node, that you're specifying as contact point?
Answer: I'm using Cassandra 2.2 and Astyanax thrift API from my Spring project, using which I am able to handle the Cassandra authentication effectively. Specify what version of Cassandra you are using and what driver you are using to connect CQL driver or Astyanax thrift API?
Question: Obviously, talking about true scale, when you can change the size of cluster without doing restarts of each node.
Answer: Yes you can scale your Cassandra cluster without restarting nodes, please check the datastax documentation for Cassandra 2.2 version:
http://docs.datastax.com/en/archived/cassandra/2.2/cassandra/operations/opsAddNodeToCluster.html
Check the datastax docs for the version you are using.

Create two nodes on a Elasticsearch run as a service

I'm using one single Linux machine and I'm running Elasticsearch as a service (I run ES with the command service elasticsearch start). My configuration has only one node so I would like to add to my cluster a new node (as a failover) to locate the replicas there.
I'm trying to follow the solution of this question but the solutions are super messy and I can't find any way to archieve my goal.
Can someone explain me (in the most clear way as I'm quite a newbye in Linux) what do I've to do to add a new node to my Elasticsearch?
Thanks in advance.
Just go to terminal and run elastic search instance again.
Your new node will be set up.You can run as many instances as you want.

Does Zookeeper need to have its own server with HAMR?

This is in regard to a big data analytics engine put out by http://hamrtech.com
Does Zookeeper have to be on its own server with HAMR?
No it does not have to be part of the hamr cluster but every node within the cluster must have access to it.

How to integrate Cassandra with Hadoop

I am trying to set up clustered Hadoop and Cassandra. Many sites I've read use a lot of words and concepts I am slowly grasping but I still need some help.
I have 3 nodes. I want to set up Hadoop and Cassandra on all 3. I am familiar with Hadoop and Cassandra individually but how so they work together and how do I configure them to work together? Also, how do I set up one node dedicated to, for example, analytics?
So far I have modified my hadoop-env.sh to point to Cassandra libs. I have put this on all of my nodes. Is that correct? What more do I need to do and how do I run it - start Hadoop cluster or Cassandra first?
Last little question: do I connect directly to Cassandra or to Hadoop from within my Java client?
Rather then connecting them via your java client, you need to install Cassandra On top of Hadoop. Please follow the article for step by step assistance.
BR

elasticsearch equivalent of EmbeddedSolrServer for Solr

Is it possible to update index built using elastic search without the overheads of http and serialization?
I am searching for an elasticsearch equivalent of EmbeddedSolrServer available with solrj.
Sure it is, with elasticsearch you can easily start up a local node and embed it in your application.
With local node I mean with local discovery, local within the jvm.
Have a look at the Java API documentation, where there's an example on how to startup a local node:
Node node = nodeBuilder().local(true).node();
Client client = node.client();
Don't forget to shut it down when you're done:
node.close();
Have a look at this blog I wrote too: elasticsearch beyond big data - running elasticsearch embedded.

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