Created function to create client pool

Author: PythonHacker24

internal/grpcpool/clientpool.go

@@ -0,0 +1,78 @@
+package grpcpool
+
+import (
+	"fmt"
+
+	"google.golang.org/grpc"
+)
+
+/* creates a new client pool */
+func NewClientPool(opts ...grpc.DialOption) *ClientPool {
+    return &ClientPool{
+        conns:       make(map[string]*grpc.ClientConn),
+        dialOptions: opts,
+		stopCh: 	 make(chan struct{}),
+    }
+}
+
+/* 
+	creates a connection to given server 
+	allows multiple connections to be established to daemons for any transactions in execution
+*/
+func (p *ClientPool) GetConn(addr string, errCh chan<-error) (*grpc.ClientConn, error) {
+	/* check if connection exists or not */
+	p.mu.RLock()
+	conn, exists := p.conns[addr]
+	p.mu.RUnlock()
+
+	/* return the connection if it exists */
+	if exists {
+		return conn, nil
+	}
+
+	/* so connection doesn't exist, create a new one */
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	/* double check again (might been created between if exists and this line) */
+	conn, exists = p.conns[addr]
+	if exists {
+        return conn, nil
+    }
+
+	/* create a new client for gRPC server */
+	newConn, err := grpc.NewClient(addr, p.dialOptions...)
+    if err != nil {
+        return nil, fmt.Errorf("failed to add new connection", err)
+    }
+
+	/* add connection to the pool */
+    p.conns[addr] = newConn
+
+	/*
+		in case of connection issues, it will remove itself from connection pool
+		when connection is demanded again, whole logic written above will be executed again 
+	*/
+	go p.MonitorHealth(addr, newConn, errCh)
+	
+	/* return connection */
+    return newConn, nil
+}
+
+/* 
+	close all connections in the pool
+	call this while error channel exists
+*/
+func (p *ClientPool) CloseAll(errCh chan<-error) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	/* iterate over all the connections and attempt to close them all */
+	for _, conn := range p.conns {
+		if err := conn.Close(); err != nil {
+			errCh <- fmt.Errorf("error while closing gRPC connection: %w", err)
+		}
+	}
+
+	p.conns = make(map[string]*grpc.ClientConn)
+}