Configure HAProxy to Send Write Requests to Leader Node Only
There are a few options regarding implementation of a proxy server to direct writes to a Master node and reads to the Slave nodes in a Neo4j cluster. Commonly, it is recommended to handle this logic in the application code. However, there is another way.
By using the following configuration for HAProxy, you can direct
GET requests (reads) to the Slave nodes, while directing everything else (
DELETE, POST, PUT) to the Master.
global daemon maxconn 256 defaults mode http timeout connect 5000ms timeout client 50000ms timeout server 50000ms frontend http-in bind *:80 acl write_methods method POST DELETE PUT #Only POST and DELETE methods are used according to the documentation use_backend neo4j-write if write_methods default_backend neo4j-read-only backend neo4j-read-only balance roundrobin option httpchk GET /db/manage/server/causalclustering/read-only server s1 10.0.1.10:7474 maxconn 32 check server s2 10.0.1.11:7474 maxconn 32 check server s3 10.0.1.12:7474 maxconn 32 check backend neo4j-write balance roundrobin option httpchk GET /db/manage/server/causalclustering/writable server s1 10.0.1.10:7474 maxconn 32 check server s2 10.0.1.11:7474 maxconn 32 check server s3 10.0.1.12:7474 maxconn 32 check
The logic here says that by default a request is routed to a follower and if it is a write request (POST, DELETE, PUT), route it to a Master instead.
See the product documentation for more info on this topic: https://neo4j.com/docs/operations-manual/3.5/ha-cluster/haproxy/
The first step in configuring Basic Authentication in HAProxy is to get the base64 representation of username:password.
To do this at the command line, for username neo4j and password neo4j:
$ echo -n "neo4j:neo4j" | base64 bmVvNGo6bmVvYWRtaW4=
Please note that this username-password combination is not valid and only used for demonstration purposes.
HTTP/1.0\r\nAuthorization:\ Basic\ base64_username_password as following:
option httpchk GET /db/manage/server/causalclustering/writable HTTP/1.0\r\nAuthorization:\ Basic\ bmVvNGo6bmVvYWRtaW4=
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