feat(docker,cache,proxy): improve container runtime defaults and add configurable connection limits

ts/classes.dcrouter.ts

@@ -528,10 +528,36 @@ export class DcRouter {
   }
 
   public async start() {
+    await this.checkSystemLimits();
     logger.log('info', 'Starting DcRouter Services');
     await this.serviceManager.start();
     this.logStartupSummary();
   }
+
+  /**
+   * Detect OS-level resource limits and warn if they are too low for production use.
+   * This is detection only — no attempts to raise limits.
+   */
+  private async checkSystemLimits(): Promise<void> {
+    try {
+      const fs = new plugins.smartfs.SmartFs(new plugins.smartfs.SmartFsProviderNode());
+      const limitsContent = await fs.file('/proc/self/limits').encoding('utf8').read() as string;
+      const nofileLine = limitsContent.split('\n').find((line: string) => line.startsWith('Max open files'));
+      if (nofileLine) {
+        const parts = nofileLine.split(/\s{2,}/);
+        const softLimit = parseInt(parts[1], 10);
+        const hardLimit = parseInt(parts[2], 10);
+        if (softLimit < 65536) {
+          logger.log('warn', `File descriptor soft limit is ${softLimit} (hard: ${hardLimit}). ` +
+            `For production use, set --ulimit nofile=65536:65536 on the container runtime.`);
+        } else {
+          logger.log('info', `File descriptor limits: soft=${softLimit}, hard=${hardLimit}`);
+        }
+      }
+    } catch {
+      // Non-Linux or /proc not available — silently skip
+    }
+  }
   
   /**
    * Log comprehensive startup summary
@@ -708,9 +734,28 @@ export class DcRouter {
       // Track cert entries loaded from cert store so we can populate certificateStatusMap after start
       const loadedCertEntries: Array<{domain: string; publicKey: string; validUntil?: number; validFrom?: number}> = [];
 
-      // Create SmartProxy configuration
+      // Create SmartProxy configuration with sensible gateway defaults.
+      // User's smartProxyConfig overrides these defaults via spread.
       const smartProxyConfig: plugins.smartproxy.ISmartProxyOptions = {
+        // --- dcrouter gateway defaults ---
+        maxConnectionsPerIP: 100,
+        connectionRateLimitPerMinute: 600,
+        socketTimeout: 120_000,
+        inactivityTimeout: 120_000,
+        keepAlive: true,
+        noDelay: true,
+        gracefulShutdownTimeout: 30_000,
+        // --- user overrides ---
         ...this.options.smartProxyConfig,
+        // --- deep-merge defaults.security so user can override maxConnections ---
+        defaults: {
+          ...this.options.smartProxyConfig?.defaults,
+          security: {
+            maxConnections: 50_000,
+            ...this.options.smartProxyConfig?.defaults?.security,
+          },
+        },
+        // --- always set by dcrouter (after spread) ---
         routes,
         acme: acmeConfig,
         certStore: {