(experimental) Add flag for using loom/virtual threads in gRPC executor

ROADMAP.md

@@ -48,10 +48,6 @@ filter for any API consumer.
 
 I've talked to the stract dev and he does not think it's a good idea to mimic their optics language, which is quite ad-hoc, but instead to work together to find some new common description language for this. 
 
-## Show favicons next to search results
-
-This is expected from search engines.  Basic proof of concept sketch of fetching this data has been done, but the feature is some way from being reality. 
-
 ## Specialized crawler for github
 
 One of the search engine's biggest limitations right now is that it does not index github at all.   A specialized crawler that fetches at least the readme.md would go a long way toward providing search capabilities in this domain.
@@ -66,6 +62,10 @@ The documents database probably should have some sort of flag indicating it's a
 PDF parsing is known to be a bit of a security liability so some thought needs to be put in
 that direction as well.
 
+## Show favicons next to search results (COMPLETED 2025-03)
+
+This is expected from search engines.  Basic proof of concept sketch of fetching this data has been done, but the feature is some way from being reality.
+
 ## Web Design Overhaul (COMPLETED 2025-01)
 
 The design is kinda clunky and hard to maintain, and needlessly outdated-looking.  

code/common/service/java/nu/marginalia/service/server/GrpcServer.java

@@ -13,9 +13,14 @@ import nu.marginalia.util.NamedExecutorFactory;
 import java.io.IOException;
 import java.net.InetSocketAddress;
 import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 public class GrpcServer {
     private final Server server;
+
+    private static final boolean useLoom = Boolean.getBoolean("system.experimentalUseLoom");
+
     public GrpcServer(ServiceConfiguration config,
                       ServiceRegistryIf serviceRegistry,
                       ServicePartition partition,
@@ -26,8 +31,13 @@ public class GrpcServer {
         int nThreads = Math.clamp(Runtime.getRuntime().availableProcessors() / 2, 2, 16);
 
         // Start the gRPC server
+
+        ExecutorService workExecutor = useLoom ?
+                Executors.newVirtualThreadPerTaskExecutor() :
+                NamedExecutorFactory.createFixed("nettyExecutor", nThreads);
+
         var grpcServerBuilder = NettyServerBuilder.forAddress(new InetSocketAddress(config.bindAddress(), port))
-                .executor(NamedExecutorFactory.createFixed("nettyExecutor", nThreads))
+                .executor(workExecutor)
                 .workerEventLoopGroup(new NioEventLoopGroup(nThreads, NamedExecutorFactory.createFixed("Worker-ELG", nThreads)))
                 .bossEventLoopGroup(new NioEventLoopGroup(nThreads, NamedExecutorFactory.createFixed("Boss-ELG", nThreads)))
                 .channelType(NioServerSocketChannel.class);