Migrate a cluster (Docker)

This example shows how to migrate a v4.4 cluster to v5.x.
Migration to Neo4j 5 is supported only from version v4.4.

It is recommended to read the following pages before continuing:

The following example steps are based on the following pre-upgrade state:

The environment has three Primary members located on three different servers a, b, c.
Neo4j DBMS v4.4 is running in a Docker container on each server with /data directory in the container mapped to /opt/data on the host machine and the container is named neo4j-dbms. You can achieve this, for instance, by running the following command on each server:
```
docker run -d \
    --name=neo4j-dbms \
    --volume=/opt/data:/data \
    neo4j:4.4-enterprise
```

Prepare your indexes and index-backed constraints for migration

Prepare the v4.4 cluster for migration by recreating the indexes and the index-backed constraints to match the new index types, and by backing up each of your databases.

In v5.0, the BTREE index type is no longer available. Therefore, it is recommended to recreate all your BTREE indexes and index-backed constraints with index providers native-btree-1.0 or lucene+native-3.0 before switching to v5.x. During the migration, v5.x checks whether each BTREE index and index-backed constraint has an equivalent type of index and provider, and drops them.

What type of index to use instead of BTREE?

In most cases, RANGE indexes can replace BTREE. However, there might be occasions when a different index type is more suitable, such as:

Use POINT indexes if the property value type is point and distance or bounding box queries are used for the property.
Use TEXT indexes if the property value type is text and the values can be larger than 8Kb.
Use TEXT indexes if the property value type is text and CONTAINS and ENDS WITH are used in queries for the property.

If more than one of the conditions is true, it is possible to have multiple indexes of different index types on the same schema. For more information on each index type, see Operations Manual v5.0 → Index configuration.

Steps

Recreate each of your BTREE indexes on the same schema but using the new type (RANGE, POINT, or TEXT) as per your use case. The following example creates a range index on a single property for all nodes with a particular label:
```
CREATE RANGE INDEX range_index_name FOR (n:Label) ON (n.prop1)
```
Recreate each of your index-backed constraints with index providers native-btree-1.0 or lucene+native-3.0 on the same schema but with the new provider. The following example creates a unique node property constraint on a single property for all nodes with a particular label. The backing index is of type range with range-1.0 index provider.
```
CREATE CONSTRAINT constraint_with_provider FOR (n:Label) REQUIRE (n.prop1) IS UNIQUE OPTIONS {indexProvider: 'range-1.0'}
```
Run SHOW INDEXES to verify that the indexes have been populated and constraints have been created with the correct index provider.

For more information about creating indexes, see Cypher Manual → Creating indexes.

Migration steps

On server a

Run SHOW DATABASES YIELD * to ensure that all databases are up-to-date with the last committed transactions. Databases can be put into read-only mode if needed using the Cypher command ALTER DATABASE database-name SET ACCESS READ ONLY.
Create a directory to store backups. This tutorial uses /opt/migration-backups.
Set the neo4j user as the owner of /opt/migration-backups to allow write access from the Neo4j docker container:
```
sudo chown neo4j:neo4j /opt/migration-backups
```
Processes in the Neo4j docker container run under the neo4j user by default.
Run the neo4j-admin backup command to back up each of your databases.
All databases that you want to back up must be online.

Use the option --include-metadata=all to include all roles and users associated with each of your databases.
```
docker run -i -t --rm -v /opt/data:/data neo4j:4.x-enterprise neo4j-admin backup --database *  --backup-dir /opt/migration-backups --include-metadata all
```
The result is a folder for each database, called <databasename> and located in the /opt/migration-backups folder, and a metadata script for each database, located in the backup directory data/scripts/databasename/restore_metadata.cypher. For more information about the neo4j-admin backup command, see Operations Manual → Back up an online database.

On each server

Stop Neo4j v4.4:
```
docker stop neo4j-dbms
```

Start Neo4j v5.x:

docker run -d --name neo4j-dbms -v /opt/data:data neo4j:5.x-enterprise

v5.x.y is expected to have no stores installed.

On server a

Run DROP DATABASE neo4j (assuming that neo4j is the default database).

Use the neo4j-admin restore command to restore the neo4j database:

docker run -i -t --rm -v /opt/data:/data neo4j:5.x-enterprise neo4j-admin database restore --from /opt/migration-backups/neo4j --database neo4j --move

Migrate the neo4j database:

docker run -i -t --rm -v /opt/data:/data neo4j:5.x-enterprise neo4j-admin database migrate --database neo4j

Repeat steps 2 and 3 for every backup in /opt/migration-backups directory except for the system database.
Run SHOW SERVERS to retrieve the server ID for server a.

Run the following command for each of your migrated databases to activate them:

CREATE DATABASE neo4j OPTIONS {existingData: 'use', existingDataSeedInstance: '[ServerId for a]'}

(Optional) Restore the roles and privileges associated with each of your databases by running the respective metadata script data/scripts/databasename/restore_metadata.cypher, which the neo4j-admin restore command output, using Cypher Shell:

Using cat (UNIX)

cat data/scripts/databasename/restore_metadata.cypher | bin/cypher-shell -u user -p password -a ip_address:port -d system --param "database => 'databasename'"

Using type (Windows)*

type data\scripts\databasename\restore_metadata.cypher | bin\cypher-shell.bat -u user -p password -a ip_address:port -d system --param "database => 'databasename'"

Run REALLOCATE DATABASES to evenly distribute your databases among the servers.

Monitor the logs

The neo4j.log file contains information on how many steps the upgrade will involve and how far it has progressed.

Neo4j logging output is written to files in the /logs directory. This directory is mounted as a /logs volume.

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