synchronized void destroy() {
            if (this.executor != null) {
                LOG.info("Destroyed peer request context for {}/{}", this.groupId, this.pair);
                this.executor.shutdownGracefully();
                this.executor = null;
            }
        }
A peer pair
@author boyan(boyan@antfin.com)
jraft-core/src/main/java/com/alipay/sofa/jraft/rpc/impl/core/AppendEntriesRequestProcessor.java