Use a pool of detectors.

When more than a single request was coming in at a time, the server
would crash when trying to write the output file. Each worker had a
single detector with one DN network, so if more than <WORKER#> requests
came in at once, one network would be used multiple times--and it's not
threadsafe.

I've added a queue of nets to pull from, so each request has exclusive
access to a specific network.

objectifier-module.nix

@@ -36,6 +36,18 @@ in {
       default = [ "127.0.0.1" ];
     };
 
+    pool-size = mkOption {
+      type = int;
+      description = "Number of nets to initialize.";
+      default = 5;
+    };
+
+    detection-timeout = mkOption {
+      type = int;
+      description = "Time in seconds to allow for detection to start.";
+      default = 5;
+    };
+
     cleanup = {
       max_file_age = mkOption {
         type = int;
@@ -63,6 +75,8 @@ in {
         OBJECTIFIER_BUFFER_SIZE = "524288";
         OBJECTIFIER_CLEANUP_MAX_AGE = toString cfg.cleanup.max_file_age;
         OBJECTIFIER_CLEANUP_DELAY = toString cfg.cleanup.delay;
+        OBJECTIFIER_TIMEOUT = toString cfg.detection-timeout;
+        OBJECTIFIER_POOL_SIZE = toString cfg.pool-size;
       };
       serviceConfig = {
         PrivateUsers = true;