Adds additional metrics for remaining capacity, min, and max

README.md

@@ -100,6 +100,12 @@ try {
   }
 }
 
+// returns the maximum number of resources allowed by the pool. This can be configured when the pool is created.
+pool.numMax();
+
+// returns the minimum number of resources allowed by the pool. This can be configured when the pool is created.
+pool.numMin();
+
 // releases the resource.
 pool.release(resource);
 
@@ -115,6 +121,9 @@ pool.numPendingAcquires();
 // how many asynchronous create calls are running
 pool.numPendingCreates();
 
+// the number of additional resources which can be created before the maximum is reached. This already deducts the number of resources that are currently being created.
+pool.numRemainingCapacity();
+
 // waits for all resources to be returned to the pool and destroys them.
 // pool cannot be used after this.
 await pool.destroy();

src/Pool.ts

@@ -164,6 +164,14 @@ export class Pool<T> {
     this.eventId = 1;
   }
 
+  numMax() {
+    return this.max;
+  }
+
+  numMin() {
+    return this.min;
+  }
+
   numUsed() {
     return this.used.length;
   }
@@ -184,6 +192,15 @@ export class Pool<T> {
     return this.pendingCreates.length;
   }
 
+  numRemainingCapacity() {
+    const demand =
+      this.numUsed() +
+      this.numPendingCreates() +
+      this.numPendingValidations() +
+      this.numPendingAcquires();
+    return Math.max(0, this.numMax() - demand);
+  }
+
   acquire() {
     const eventId = this.eventId++;
     this._executeEventHandlers('acquireRequest', eventId);