nixos/cassandra: Prepare for cassandra 4

Its scripts disagree a bit with our flexible
logging approach and our default logging config.
Might want to revisit this at some point.

The `mkdir` failures in the log are harmless.

nixos/modules/services/databases/cassandra.nix

@@ -21,6 +21,7 @@ let
 
   atLeast3 = versionAtLeast cfg.package.version "3";
   atLeast3_11 = versionAtLeast cfg.package.version "3.11";
+  atLeast4 = versionAtLeast cfg.package.version "4";
 
   defaultUser = "cassandra";
 
@@ -65,7 +66,7 @@ let
     cassandraLogbackConfig = pkgs.writeText "logback.xml" cfg.logbackConfig;
 
     passAsFile = [ "extraEnvSh" ];
-    inherit (cfg) extraEnvSh;
+    inherit (cfg) extraEnvSh package;
 
     buildCommand = ''
       mkdir -p "$out"
@@ -83,6 +84,10 @@ let
 
       # Delete default password file
       sed -i '/-Dcom.sun.management.jmxremote.password.file=\/etc\/cassandra\/jmxremote.password/d' "$out/cassandra-env.sh"
+
+      ${lib.optionalString atLeast4 ''
+        cp $package/conf/jvm*.options $out/
+      ''}
     '';
   };
 
@@ -98,8 +103,20 @@ let
       "-Dcom.sun.management.jmxremote.password.file=${cfg.jmxRolesFile}"
     ] ++ optionals cfg.remoteJmx [
       "-Djava.rmi.server.hostname=${cfg.rpcAddress}"
+    ] ++ optionals atLeast4 [
+      # Historically, we don't use a log dir, whereas the upstream scripts do
+      # expect this. We override those by providing our own -Xlog:gc flag.
+      "-Xlog:gc=warning,heap*=warning,age*=warning,safepoint=warning,promotion*=warning"
     ];
 
+  commonEnv = {
+    # Sufficient for cassandra 2.x, 3.x
+    CASSANDRA_CONF = "${cassandraEtc}";
+
+    # Required since cassandra 4
+    CASSANDRA_LOGBACK_CONF = "${cassandraEtc}/logback.xml";
+  };
+
 in
 {
   options.services.cassandra = {
@@ -489,8 +506,7 @@ in
     systemd.services.cassandra = {
       description = "Apache Cassandra service";
       after = [ "network.target" ];
-      environment = {
+      environment = commonEnv // {
-        CASSANDRA_CONF = "${cassandraEtc}";
         JVM_OPTS = builtins.concatStringsSep " " fullJvmOptions;
         MAX_HEAP_SIZE = toString cfg.maxHeapSize;
         HEAP_NEWSIZE = toString cfg.heapNewSize;
@@ -511,6 +527,7 @@ in
       description = "Perform a full repair on this Cassandra node";
       after = [ "cassandra.service" ];
       requires = [ "cassandra.service" ];
+      environment = commonEnv;
       serviceConfig = {
         User = cfg.user;
         Group = cfg.group;
@@ -539,6 +556,7 @@ in
       description = "Perform an incremental repair on this cassandra node.";
       after = [ "cassandra.service" ];
       requires = [ "cassandra.service" ];
+      environment = commonEnv;
       serviceConfig = {
         User = cfg.user;
         Group = cfg.group;