Xoken Nexa Prerequisites

Nexa Prerequisites
Setting Up Cassandra
Prerequisites

Install Oracle Java Standard Edition 8 and Python 2.7 from your distro's package manager.

Installation 

We are going to install all the necessary software under /opt directory which has sufficient disk space (ideally 1 TB) and is mounted on an SSD.

Download Apache Cassandra 3.11.6 from this official download link and unarchive directly under /opt.

Configuration

Edit the config file (/opt/apache-cassandra-3.11.6/conf/cassandra.yaml)

Update the listen address appropriately,

listen_address: localhost

Also tweak the below settings appropriately per the instructions provided in the config file. The below sample values are good for a 12 core machine

concurrent_reads: 32 
concurrent_writes: 96 
concurrent_counter_writes: 32

Also explicitly set the max threads configuration as below,

native_transport_max_threads: 256

To facilitate the highly concurrent application, make the following system configurations, it primarily is meant to help Cassandra operate optimally.

/etc/security/limits.conf
* - memlock unlimited
* - nofile 100000
* - nproc 32768
* - as unlimited

/etc/sysctl.conf
vm.max_map_count = 1048575

Set the PATH environment variable as follows in your .bashrc file:

export PATH=$PATH:/opt/apache-cassandra-3.11.6/bin

Cassandra can be started using the following command

$cassandra

To stop Cassandra, we can simply get the processID and kill it.

$ps -ef |grep cassandra
$kill -9 <pid>

Database schema setup

Login to CQL shell (cqlsh) and execute the contents of the schema.cql file that was included in the release.

Setting Up Neo4j
Installation

Download the official (3.5.20) release of Neo4j from here and unarchive the same under /opt.

Note: Only Neo4j version "3.5.x" is officially supported. The packaged Neo4j driver does NOT support versions 4.x.x.

Configuration

Edit the config file at /opt/neo4j-community-3.5.20/conf/neo4j.conf and add the following at the bottom of the file

dbms.connector.bolt.thread_pool_min_size=20
dbms.connector.bolt.thread_pool_max_size=2048
dbms.connector.bolt.thread_pool_keep_alive=5m

Also uncomment and update the following entry appropriately,

dbms.connector.default_listen_address=0.0.0.0

Login to the Neo4j web console (http://localhost:7474/) and execute the following: 

CREATE CONSTRAINT ON (n:mnode) ASSERT n.v IS UNIQUE;

You can verify if the constraints have been applied correctly by querying 

$ :schema

And you should see the following output, 

Indexes
ON :mnode(v) ONLINE  (for uniqueness constraint)

Constraints
   ON ( mnode:mnode ) ASSERT mnode.v IS UNIQUE

Set the PATH environment variable as follows in your .bashrc file:

export PATH=$PATH:/opt/apache-cassandra-3.11.6/bin:/opt/neo4j-community-3.5.20/bin

neo4j can be started and stopped using the following command/s

$neo4j [start/stop/restart]
Other packages

Using the appropriate package manager for your Linux distribution install the below packages. For example on Arch variants run,

sudo pacman -S libsecp256k1
sudo pacman -S leveldb


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