Add max cache size for initial context cache.

Author: dlongley

lib/context.js

@@ -24,6 +24,7 @@ const {
 const MAX_CONTEXT_URLS = 10;
 
 const INITIAL_CONTEXT_CACHE = new Map();
+const INITIAL_CONTEXT_CACHE_MAX_SIZE = 10000;
 
 const api = {};
 module.exports = api;
@@ -646,6 +647,9 @@ api.getInitialContext = (options) => {
     getInverse: _createInverseContext,
     clone: _cloneActiveContext
   };
+  if(INITIAL_CONTEXT_CACHE.size === INITIAL_CONTEXT_CACHE_MAX_SIZE) {
+    INITIAL_CONTEXT_CACHE.delete(INITIAL_CONTEXT_CACHE.keys().next().value);
+  }
   INITIAL_CONTEXT_CACHE.set(key, initialContext);
   return initialContext;