nixpkgs/nixos/modules/services/databases/neo4j.nix

{ config, lib, pkgs, ... }:

with lib;

let
  cfg = config.services.neo4j;

  serverConfig = pkgs.writeText "neo4j.conf" ''
    dbms.directories.data=${cfg.dataDir}/data
    dbms.directories.certificates=${cfg.certDir}
    dbms.directories.logs=${cfg.dataDir}/logs
    dbms.directories.plugins=${cfg.dataDir}/plugins
    dbms.connector.http.type=HTTP
    dbms.connector.http.enabled=true
    dbms.connector.http.address=${cfg.listenAddress}:${toString cfg.port}
    ${optionalString cfg.enableBolt ''
      dbms.connector.bolt.type=BOLT
      dbms.connector.bolt.enabled=true
      dbms.connector.bolt.tls_level=OPTIONAL
      dbms.connector.bolt.address=${cfg.listenAddress}:${toString cfg.boltPort}
    ''}
    ${optionalString cfg.enableHttps ''
      dbms.connector.https.type=HTTP
      dbms.connector.https.enabled=true
      dbms.connector.https.encryption=TLS
      dbms.connector.https.address=${cfg.listenAddress}:${toString cfg.httpsPort}
    ''}
    dbms.shell.enabled=true
    ${cfg.extraServerConfig}

    # Default JVM parameters from neo4j.conf
    dbms.jvm.additional=-XX:+UseG1GC
    dbms.jvm.additional=-XX:-OmitStackTraceInFastThrow
    dbms.jvm.additional=-XX:+AlwaysPreTouch
    dbms.jvm.additional=-XX:+UnlockExperimentalVMOptions
    dbms.jvm.additional=-XX:+TrustFinalNonStaticFields
    dbms.jvm.additional=-XX:+DisableExplicitGC
    dbms.jvm.additional=-Djdk.tls.ephemeralDHKeySize=2048

    dbms.jvm.additional=-Dunsupported.dbms.udc.source=tarball
  '';

in {

  ###### interface

  options.services.neo4j = {
    enable = mkOption {
      description = "Whether to enable neo4j.";
      default = false;
      type = types.bool;
    };

    package = mkOption {
      description = "Neo4j package to use.";
      default = pkgs.neo4j;
      defaultText = "pkgs.neo4j";
      type = types.package;
    };

    listenAddress = mkOption {
      description = "Neo4j listen address.";
      default = "127.0.0.1";
      type = types.str;
    };

    port = mkOption {
      description = "Neo4j port to listen for HTTP traffic.";
      default = 7474;
      type = types.int;
    };

    enableBolt = mkOption {
      description = "Enable bolt for Neo4j.";
      default = true;
      type = types.bool;
    };

    boltPort = mkOption {
      description = "Neo4j port to listen for BOLT traffic.";
      default = 7687;
      type = types.int;
    };

    enableHttps = mkOption {
      description = "Enable https for Neo4j.";
      default = false;
      type = types.bool;
    };

    httpsPort = mkOption {
      description = "Neo4j port to listen for HTTPS traffic.";
      default = 7473;
      type = types.int;
    };

    certDir = mkOption {
      description = "Neo4j TLS certificates directory.";
      default = "${cfg.dataDir}/certificates";
      type = types.path;
    };

    dataDir = mkOption {
      description = "Neo4j data directory.";
      default = "/var/lib/neo4j";
      type = types.path;
    };

    extraServerConfig = mkOption {
      description = "Extra configuration for neo4j server.";
      default = "";
      type = types.lines;
    };
  };

  ###### implementation

  config = mkIf cfg.enable {
    systemd.services.neo4j = {
      description = "Neo4j Daemon";
      wantedBy = [ "multi-user.target" ];
      after = [ "network.target" ];
      environment = {
        NEO4J_HOME = "${cfg.package}/share/neo4j";
        NEO4J_CONF = "${cfg.dataDir}/conf";
      };
      serviceConfig = {
        ExecStart = "${cfg.package}/bin/neo4j console";
        User = "neo4j";
        PermissionsStartOnly = true;
        LimitNOFILE = 40000;
      };
      preStart = ''
        mkdir -m 0700 -p ${cfg.dataDir}/{data/graph.db,conf,logs}
        ln -fs ${serverConfig} ${cfg.dataDir}/conf/neo4j.conf
        if [ "$(id -u)" = 0 ]; then chown -R neo4j ${cfg.dataDir}; fi
      '';
    };

    environment.systemPackages = [ cfg.package ];

    users.extraUsers = singleton {
      name = "neo4j";
      uid = config.ids.uids.neo4j;
      description = "Neo4j daemon user";
      home = cfg.dataDir;
    };
  };
}