cassandra: init service (#116)

* cassandra: init service

* cassandra: add cassandra/conf files

* cassandra_test: change package to cassandra_4

* update readiness_probe

* update cassandra_test

* cassandra: add doc

* cassandra_4 doesn't require python-2

---------

Co-authored-by: shivaraj-bh <sbh69840@gmail.com>

doc/cassandra.md

@@ -0,0 +1,31 @@
+# Cassandra
+
+[Cassandra] is a free and open-source, distributed, wide-column store, NoSQL database management system designed to handle large amounts of data across many commodity servers, providing high availability with no single point of failure.
+
+[Cassandra]: https://cassandra.apache.org/_/index.html
+
+## Getting Started
+
+```nix
+# In `perSystem.process-compose.<name>`
+{
+  services.cassandra."cass1".enable = true;
+}
+```
+
+{#tips}
+## Tips & Tricks
+
+{#change-port}
+### Change the default port
+
+By default, the Cassandra server is started on port `9042`. To change the port, we can use the following config:
+
+```nix
+{
+  services.cassandra."cass1" = {
+    enable = true;
+    nativeTransportPort = 9043;
+  };
+}
+```

doc/services.md

@@ -19,6 +19,7 @@ short-title: Services
 - [x] [[grafana]]#
 - [X] [[prometheus]]#
 - [X] [[pgadmin]]#
+- [X] [[cassandra]]#
 - [ ] ...
 
 [gh]: https://github.com/juspay/services-flake

nix/cassandra.nix

@@ -0,0 +1,169 @@
+# Based on https://github.com/cachix/devenv/blob/fa9a708e240c6174f9fc4c6eefbc6a89ce01c350/src/modules/services/cassandra.nix
+{ pkgs, lib, name, config, ... }:
+let
+  inherit (lib) types;
+  yamlFormat = pkgs.formats.yaml { };
+in
+{
+  options = {
+    enable = lib.mkEnableOption name;
+
+    package = lib.mkPackageOption pkgs "cassandra" { };
+
+    dataDir = lib.mkOption {
+      type = types.str;
+      default = "./data/${name}";
+      description = "The cassandra data directory";
+    };
+
+    listenAddress = lib.mkOption {
+      type = types.str;
+      description = "Listen address";
+      default = "127.0.0.1";
+      example = "127.0.0.1";
+    };
+
+    nativeTransportPort = lib.mkOption {
+      type = types.port;
+      description = "port for the CQL native transport to listen for clients on";
+      default = 9042;
+    };
+
+    seedAddresses = lib.mkOption {
+      type = types.listOf types.str;
+      default = [ "127.0.0.1" ];
+      description = "The addresses of hosts designated as contact points of the cluster";
+    };
+
+    clusterName = lib.mkOption {
+      type = types.str;
+      default = "Test Cluster";
+      description = "The name of the cluster";
+    };
+
+    allowClients = lib.mkOption {
+      type = types.bool;
+      default = true;
+      description = ''
+        Enables or disables the native transport server (CQL binary protocol)
+      '';
+    };
+
+    extraConfig = lib.mkOption {
+      type = yamlFormat.type;
+      default = { };
+      example =
+        {
+          commitlog_sync_batch_window_in_ms = 3;
+        };
+      description = ''
+        Extra options to be merged into `cassandra.yaml` as nix attribute set.
+      '';
+    };
+
+    jvmOpts = lib.mkOption {
+      type = types.listOf types.str;
+      default = [ ];
+      description = "Options to pass to the JVM through the JVM_OPTS environment variable";
+    };
+
+    defaultExtraConfig = lib.mkOption {
+      type = yamlFormat.type;
+      internal = true;
+      readOnly = true;
+      default = {
+        start_native_transport = config.allowClients;
+        listen_address = config.listenAddress;
+        native_transport_port = config.nativeTransportPort;
+        commitlog_sync = "batch";
+        commitlog_sync_batch_window_in_ms = 2;
+        cluster_name = config.clusterName;
+        partitioner = "org.apache.cassandra.dht.Murmur3Partitioner";
+        endpoint_snitch = "SimpleSnitch";
+        data_file_directories = [ "${config.dataDir}/data" ];
+        commitlog_directory = "${config.dataDir}/commitlog";
+        saved_caches_directory = "${config.dataDir}/saved_caches";
+        hints_directory = "${config.dataDir}/hints";
+        seed_provider = [
+          {
+            class_name = "org.apache.cassandra.locator.SimpleSeedProvider";
+            parameters = [{ seeds = lib.concatStringsSep "," config.seedAddresses; }];
+          }
+        ];
+      };
+    };
+
+    outputs.settings = lib.mkOption {
+      type = types.deferredModule;
+      internal = true;
+      readOnly = true;
+      default = {
+        processes = {
+          "${name}" =
+            let
+              cassandraConfig = pkgs.stdenv.mkDerivation {
+                name = "cassandra-config";
+                cassandraYaml = yamlFormat.generate "cassandra.yaml" (
+                  lib.recursiveUpdate config.defaultExtraConfig config.extraConfig
+                );
+                buildCommand = ''
+                  mkdir -p $out
+                  for d in ${config.package}/conf/*; do ln -s "$d" $out/; done
+                  rm -rf $out/cassandra.y*ml
+                  ln -s "$cassandraYaml" "$out/cassandra.yaml"
+
+                  rm -rf $out/cassandra-env.sh
+                  cat ${config.package}/conf/cassandra-env.sh > $out/cassandra-env.sh
+                  LOCAL_JVM_OPTS="${lib.concatStringsSep " " config.jvmOpts}"
+                  echo "JVM_OPTS=\"\$JVM_OPTS $LOCAL_JVM_OPTS\"" >> $out/cassandra-env.sh
+                '';
+              };
+
+              startScript = pkgs.writeShellScriptBin "start-cassandra" ''
+                set -euo pipefail
+
+                DATA_DIR="$(readlink -m ${config.dataDir})"
+                if [[ ! -d "$DATA_DIR" ]]; then
+                  mkdir -p "$DATA_DIR"
+                fi
+
+                CASSANDRA_CONF="${cassandraConfig}"
+                export CASSANDRA_CONF
+
+                CASSANDRA_LOG_DIR="$DATA_DIR/log/"
+                mkdir -p "$CASSANDRA_LOG_DIR"
+                export CASSANDRA_LOG_DIR
+
+                CASSANDRA_HOME="${config.package}"
+                export CASSANDRA_HOME
+
+                CLASSPATH="${config.package}/lib"
+                export CLASSPATH
+
+                export LOCAL_JMX="yes"
+                exec ${config.package}/bin/cassandra -f
+              '';
+            in
+            {
+              command = startScript;
+
+              readiness_probe = {
+                exec.command = ''
+                  echo 'show version;' | CQLSH_HOST=${config.listenAddress} CQLSH_PORT=${toString config.nativeTransportPort} ${config.package}/bin/cqlsh
+                '';
+                initial_delay_seconds = 2;
+                period_seconds = 10;
+                timeout_seconds = 4;
+                success_threshold = 1;
+                failure_threshold = 5;
+              };
+              namespace = name;
+
+              # https://github.com/F1bonacc1/process-compose#-auto-restart-if-not-healthy
+              availability.restart = "on_failure";
+            };
+        };
+      };
+    };
+  };
+}

nix/cassandra_test.nix

@@ -0,0 +1,27 @@
+{ pkgs, config, ... }: {
+  services.cassandra."cass1" = {
+    enable = true;
+    # support for aarch64-darwin was added in cassandra-4
+    # https://github.com/apache/cassandra/blob/a87055d56a33a9b17606f14535f48eb461965b82/CHANGES.txt#L192
+    package = pkgs.cassandra_4;
+  };
+
+  settings.processes.test =
+    let
+      cfg = config.services.cassandra."cass1";
+    in
+    {
+      command = pkgs.writeShellApplication {
+        runtimeInputs = [ cfg.package ];
+        text = ''
+          echo "show version;" | cqlsh
+          echo "create keyspace test with replication = {'class': 'SimpleStrategy', 'replication_factor': 1};" | cqlsh
+          echo "CREATE TABLE test.test_table(id int PRIMARY KEY, name text);" | cqlsh
+          echo "insert into test.test_table (id, name) VALUES (1, 'hello');" | cqlsh
+          echo "select * from test.test_table;" | cqlsh | grep hello
+        '';
+        name = "cassandra-test";
+      };
+      depends_on."cass1".condition = "process_healthy";
+    };
+}

nix/default.nix

@@ -16,5 +16,6 @@ in
     ./grafana.nix
     ./prometheus.nix
     ./pgadmin.nix
+    ./cassandra.nix
   ];
 }

test/flake.nix

@@ -55,6 +55,7 @@
             "${inputs.services-flake}/nix/grafana_test.nix"
             "${inputs.services-flake}/nix/prometheus_test.nix"
             "${inputs.services-flake}/nix/pgadmin_test.nix"
+            "${inputs.services-flake}/nix/cassandra_test.nix"
           ]);
       };
     };