Cluster: org.neo4j.kernel.impl.transaction.log.NoSuchTransactionException: Unable to find transaction 1 in any of my logical logs: Couldn’t find any log containing 1

When operating a causal cluster, if “the store” (data/databases/graph.db) is removed from a server that was previously a member of the cluster we will get the following exception when that server is started: java.lang.RuntimeException: Error starting org.neo4j.kernel.impl.factory.GraphDatabaseFacadeFactory, /path/to/neo4j/data/databases/graph.db at org.neo4j.kernel.impl.factory.GraphDatabaseFacadeFactory.initFacade(GraphDatabaseFacadeFactory.java:209)… Read more →

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Causal Cluster FAQ for heavy workloads

Lagging of follower instances and what causes it? The main reason for followers to fall behind is highly concurrent and continuous read/write workloads. This can cause the instances get overwhelmed which causes some extra latency in propagating the data to… Read more →

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A light weight approach to validating network port connectivity

If it becomes necessary to validate, particularly in a clustered environment whether Causal Cluster or High Availability, whether or not 1 instance can talk to another instance on a given port one can use linux command netcat. To Validate connectivity… Read more →

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Are my cluster transactions/messages encrypted.

For all versions prior to 3.3, there is no encryption done specifically on the contents being transferred. Furthermore, since it doesn’t use REST or Bolt, there is no SSL/https configuration either. Transactions are propagated via transaction logs, which are a… Read more →

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A demonstration of IntraCluster SSL Encryption

This document provides a step-by-step demonstration of the process to deploy a Self-Signed SSL Certificate, to member instances of a Causal Cluster, aimed at achieving intra-cluster encryption. The steps can be outlined as: Generate and install cryptographic objects Create an SSL… Read more →

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An example of neo4j-import steps in a Causal Cluster environment

The following steps are provided to describe how to use neo4j-import in a Causal Cluster environment and was run from an environment of a single linux host with 3 copies for Neo4j 3.1.2 installed in the following paths ~/HA/ha1/neo4j-enterprise-3.1.2 ~/HA/ha2/neo4j-enterprise-3.1.2… Read more →

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Run multiple Causal Clusters locally using Docker

It’s rather easy to run multiple causal clusters on the same server or machine. You need to ensure: Each cluster needs to run on its own Docker network Overlapping port mappings must be prevented causal_clustering.initial_discovery_members needs to contain the list… Read more →

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A Demonstration of Cluster Size at Formation and Runtime

Causal Clustering Minimum Core Size At Formation causal_clustering.minimum_core_cluster_size_at_formation is defined as the minimum number of Core machines initially required to form a cluster. The cluster will form when at least this many Core members have discovered each other. The following… Read more →

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A demonstration of causal cluster routing

The following will demonstrate how to use cypher-shell to get a better understanding of a Neo4j Causal Cluster instance and its implementation of routing. The initial scenario is described with local cluster setup with 3 core instances, 1 LEADER and… Read more →

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Setup Routing Policies for Different User Types To Direct them to Different Servers

Problem statement There is a Causal Cluster Setup with 3 Cores and 1 Read Replica. There are 2 user groups – OLTP users and OLAP users. OLTP user queries should only go to the 2 Followers and not to the… Read more →

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A method to replicate a Causal Cluster to new hardware with minimum downtime

If the opportunity arises such that you are in need of replicating your existing Causal Cluster cluster to a new hardware setup, the following can be used to allow for minimal downtime. Let us first start with an existing 3… Read more →

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How to monitor if a follower is in sync with Leader (Causal Cluster)

To monitor if a Follower is in sync with its Leader, or know how much it is lagging behind, it is possible to check the Last Commited Transaction Id from Leader and Follower. Last Commited Transaction Id can be assessed… Read more →

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Upgrading your Causal Cluster from 3.1.x to 3.2.x

This article outlines possible steps to upgrade your Neo4j 3.1.2+ Causal Cluster to 3.2.2. For this upgrade path, Neo4j does not support rolling upgrades, so downtime is required to complete the process. However, the following procedure tries to minimize the… Read more →

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How do I display a hostname rather than IP address in the Causal Clustering Members section of sysinfo

Via the browser one can enter :sysinfo to display data about the Neo4j system. When Neo4j is configured as a causal cluster, the bottom-right corner of the `:sysinfo’ output will display the members in the cluster as depicted below: Each… Read more →

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