diff --git a/README.md b/README.md
index fe9191e..6ecb5e5 100644
--- a/README.md
+++ b/README.md
@@ -53,6 +53,8 @@ NOTE: One can use "Last-Modified" or "Etag" HTTP header in response to prevent
 wasted upstream refresh actions, Especially when thousands serverlists and
 upstreams configured.
 
+NOTE: Will also segfault at runtime if you leave out the syntax for serverlist upstream in the config.
+
 ## Directives
 ### serverlist_service
 * Syntax: `serverlist_service url=http://xxx/ [conf_dump_dir=dumped_dir/] [interval=5s] [timeout=2s] [concurrency=1];`
diff --git a/ngx_http_upstream_serverlist.c b/ngx_http_upstream_serverlist.c
index 2fe5c45..9337c61 100644
--- a/ngx_http_upstream_serverlist.c
+++ b/ngx_http_upstream_serverlist.c
@@ -48,10 +48,12 @@ typedef struct {
 typedef struct {
     ngx_http_conf_ctx_t          *conf_ctx;
     ngx_pool_t                   *conf_pool;
+    ngx_pool_t                   *prev_conf_pool;
     ngx_array_t                   service_conns;
     ngx_array_t                   serverlists;
 
     ngx_uint_t                    service_concurrency;
+    ngx_int_t                     conf_pool_count;
     ngx_url_t                     service_url;
     ngx_str_t                     conf_dump_dir;
 } main_conf;
@@ -74,9 +76,6 @@ init_module(ngx_cycle_t *cycle);
 static ngx_int_t
 init_process(ngx_cycle_t *cycle);
 
-static void
-exit_process(ngx_cycle_t *cycle);
-
 static void
 refresh_timeout_handler(ngx_event_t *ev);
 
@@ -134,7 +133,7 @@ ngx_module_t ngx_http_upstream_serverlist_module = {
     init_process,                          /* init process */
     NULL,                                  /* init thread */
     NULL,                                  /* exit thread */
-    exit_process,                          /* exit process */
+    NULL,                          /* exit process */
     NULL,                                  /* exit master */
     NGX_MODULE_V1_PADDING
 };
@@ -170,7 +169,7 @@ create_main_conf(ngx_conf_t *cf) {
         return NULL;
     }
 
-     if (ngx_array_init(&mcf->service_conns, cf->pool, 1,
+    if (ngx_array_init(&mcf->service_conns, cf->pool, 1,
             sizeof(service_conn)) != NGX_OK) {
         return NULL;
     }
@@ -183,6 +182,8 @@ create_main_conf(ngx_conf_t *cf) {
     mcf->service_concurrency = DEFAULT_SERVICE_CONCURRENCY;
     mcf->conf_ctx = cf->ctx;
     mcf->conf_pool = cf->pool;
+    mcf->conf_pool_count = 0; 
+    
     return mcf;
 }
 
@@ -456,29 +457,6 @@ init_process(ngx_cycle_t *cycle) {
     return NGX_OK;
 }
 
-static void
-exit_process(ngx_cycle_t *cycle) {
-    main_conf *mcf = ngx_http_cycle_get_module_main_conf(cycle,
-        ngx_http_upstream_serverlist_module);
-    serverlist *sls = mcf->serverlists.elts;
-    service_conn *scs = mcf->service_conns.elts;
-    ngx_uint_t i;
-
-    for (i = 0; i < mcf->serverlists.nelts; i++) {
-        if (sls[i].pool) {
-            ngx_destroy_pool(sls[i].pool);
-            sls[i].pool = NULL;
-        }
-    }
-
-    for (i = 0; i < mcf->service_conns.nelts; i++) {
-        if (scs[i].peer_conn.connection) {
-            ngx_close_connection(scs[i].peer_conn.connection);
-            scs[i].peer_conn.connection = NULL;
-        }
-    }
-}
-
 static void
 empty_handler(ngx_event_t *ev) {
     ngx_log_debug(NGX_LOG_DEBUG_ALL, ev->log, 0,
@@ -833,6 +811,7 @@ get_one_line(u_char *buf, u_char *buf_end, ngx_str_t *line) {
 static ngx_array_t *
 get_servers(ngx_pool_t *pool, ngx_str_t *body, ngx_log_t *log) {
     ngx_int_t ret = -1;
+    // this is the pool that needs to be cleared
     ngx_array_t *servers = ngx_array_create(pool, 2,
         sizeof(ngx_http_upstream_server_t));
     ngx_http_upstream_server_t *server = NULL;
@@ -871,6 +850,7 @@ get_servers(ngx_pool_t *pool, ngx_str_t *body, ngx_log_t *log) {
                     break;
                 }
 
+                // this causes the memory leak when servers are never removed
                 server = ngx_array_push(servers);
                 ngx_memzero(server, sizeof *server);
                 server->name = u.url;
@@ -1091,14 +1071,77 @@ refresh_upstream(serverlist *sl, ngx_str_t *body, ngx_log_t *log) {
     main_conf *mcf = ngx_http_cycle_get_module_main_conf(ngx_cycle,
         ngx_http_upstream_serverlist_module);
     ngx_http_upstream_srv_conf_t *uscf = sl->upstream_conf;
-    ngx_http_upstream_init_pt init = NULL;
     ngx_conf_t cf = {0};
-    ngx_array_t *new_servers = NULL;
-    ngx_array_t *old_servers = uscf->servers;
+    ngx_array_t *new_servers = NULL;    
+
+    // create new temp main_conf with a new pools, new service_conns and new serverlists, copy info from existing conf except for the pools, service_conns and serverlists
+    cf.pool = ngx_create_pool(NGX_DEFAULT_POOL_SIZE, log);
+
+    ngx_http_conf_ctx_t *ctx = NULL;
+    ctx = ngx_pcalloc(cf.pool, sizeof(ngx_http_conf_ctx_t));
+    if (ctx == NULL) {
+        return -1;
+    }
+    ctx = mcf->conf_ctx;
+    cf.ctx = ctx;
 
-    // use mcf->pool, avoid coredump, will lead mem leak
-    // new_servers = get_servers(sl->new_pool, body, log);
-    new_servers = get_servers(mcf->conf_pool, body, log);
+    main_conf *tmp_mcf = create_main_conf(&cf);
+
+    //copy over previous count
+    tmp_mcf->conf_pool_count = mcf->conf_pool_count;
+    
+
+    // create new server list
+    serverlist *new_sl = NULL;
+    new_sl = ngx_array_push(&tmp_mcf->serverlists);
+    if (new_sl == NULL) {
+        ngx_log_error(NGX_LOG_ERR, log, 0,
+            "upstream-serverlist: temp serverlists conf %V failed", uscf->host);
+        return -1;
+    }
+    ngx_memzero(new_sl, sizeof *new_sl);
+    new_sl->upstream_conf = uscf;
+    new_sl->last_modified = -1;
+    new_sl->name = uscf->host;
+
+    tmp_mcf->service_concurrency = mcf->service_concurrency;
+    tmp_mcf->service_url = mcf->service_url;
+    tmp_mcf->conf_dump_dir = mcf->conf_dump_dir;
+
+    //create new conns
+    service_conn *new_sc = NULL;
+    new_sc = ngx_array_push(&tmp_mcf->service_conns);
+    ngx_memzero(new_sc, sizeof *new_sc);
+    new_sc->send.start = ngx_pcalloc(tmp_mcf->conf_pool, MAX_HTTP_REQUEST_SIZE);
+    if (new_sc->send.start == NULL) {
+        ngx_log_error(NGX_LOG_ERR, log, 0,
+            "upstream-serverlist: new allocate send buffer failed");
+        return NGX_ERROR;
+    }
+    new_sc->send.end = new_sc->send.start + MAX_HTTP_REQUEST_SIZE;
+    new_sc->send.last = new_sc->send.pos = new_sc->send.start;
+
+    new_sc->recv.start = ngx_pcalloc(tmp_mcf->conf_pool, ngx_pagesize);
+    if (new_sc->recv.start == NULL) {
+        ngx_log_error(NGX_LOG_ERR, log, 0,
+            "upstream-serverlist: new allocate recv buffer failed");
+        return NGX_ERROR;
+    }
+    new_sc->recv.end = new_sc->recv.start + MAX_HTTP_REQUEST_SIZE;
+    new_sc->recv.last = new_sc->recv.pos = new_sc->recv.start;
+
+    ngx_memzero(&new_sc->peer_conn, sizeof new_sc->peer_conn);
+    new_sc->peer_conn.data = NULL;
+    new_sc->peer_conn.log = log;
+    new_sc->peer_conn.log_error = NGX_ERROR_ERR;
+    new_sc->peer_conn.connection = NULL;
+    new_sc->peer_conn.get = ngx_event_get_peer;
+    new_sc->peer_conn.name = &tmp_mcf->service_url.host;
+    new_sc->peer_conn.sockaddr = &tmp_mcf->service_url.sockaddr.sockaddr;
+    new_sc->peer_conn.socklen = tmp_mcf->service_url.socklen;
+
+    //new_servers = get_servers(mcf->conf_pool, body, log);
+    new_servers = get_servers(tmp_mcf->conf_pool, body, log);
     if (new_servers == NULL || new_servers->nelts <= 0) {
         ngx_log_error(NGX_LOG_ERR, log, 0,
             "upstream-serverlist: parse serverlist %V failed", &sl->name);
@@ -1106,6 +1149,11 @@ refresh_upstream(serverlist *sl, ngx_str_t *body, ngx_log_t *log) {
     }
 
     if (!upstream_servers_changed(uscf->servers, new_servers)) {
+        if (tmp_mcf->conf_pool != NULL) {
+            // destry temp pool
+            ngx_destroy_pool(tmp_mcf->conf_pool);
+            tmp_mcf->conf_pool = NULL;
+        }
         ngx_log_debug(NGX_LOG_INFO, log, 0,
             "upstream-serverlist: serverlist %V nothing changed",&sl->name);
         // once return -1, everything in the old pool will kept and the new pool
@@ -1113,29 +1161,64 @@ refresh_upstream(serverlist *sl, ngx_str_t *body, ngx_log_t *log) {
         return -1;
     }
 
-    init = uscf->peer.init_upstream ? uscf->peer.init_upstream
-        : ngx_http_upstream_init_round_robin;
 
     ngx_memzero(&cf, sizeof cf);
     cf.name = "serverlist_init_upstream";
     cf.cycle = (ngx_cycle_t *) ngx_cycle;
-    // cf.pool = sl->new_pool;
-    cf.pool = mcf->conf_pool;
+
+    
+    cf.pool = tmp_mcf->conf_pool;
     cf.module_type = NGX_HTTP_MODULE;
     cf.cmd_type = NGX_HTTP_MAIN_CONF;
     cf.log = ngx_cycle->log;
-    cf.ctx = mcf->conf_ctx;
+    cf.ctx = tmp_mcf->conf_ctx;
 
-    old_servers = uscf->servers;
+    ngx_array_t *old_servers = uscf->servers;
     uscf->servers = new_servers;
 
-    if (init(&cf, uscf) != NGX_OK) {
+    ngx_array_t *old_service_conns = &mcf->service_conns;
+    ngx_array_t *old_serverlists = &mcf->serverlists;
+
+    ngx_uint_t blocksize = 0;
+    if (tmp_mcf->serverlists.nelts >= tmp_mcf->service_concurrency) {
+        blocksize = (tmp_mcf->serverlists.nelts + (tmp_mcf->service_concurrency - 1))
+            / tmp_mcf->service_concurrency;
+    } else {
+        blocksize = 1;
+    }
+
+    new_sc->serverlists_start = ngx_min(tmp_mcf->serverlists.nelts,
+            0 + blocksize);
+    new_sc->serverlists_end = ngx_min(tmp_mcf->serverlists.nelts,
+            new_sc->serverlists_start + blocksize);
+    new_sc->serverlists_curr = new_sc->serverlists_start;
+
+    for (ngx_uint_t i = 0; i < tmp_mcf->service_conns.nelts; i++) {
+        service_conn *tmp_sc = (service_conn *)tmp_mcf->service_conns.elts + i;
+        tmp_sc->timeout_timer.handler = refresh_timeout_handler;
+        tmp_sc->timeout_timer.log = log;
+        tmp_sc->timeout_timer.data = tmp_sc;
+        tmp_sc->refresh_timer.handler = connect_to_service;
+        tmp_sc->refresh_timer.log = log;
+        tmp_sc->refresh_timer.data = tmp_sc;
+        if ((ngx_uint_t)tmp_sc->serverlists_start < tmp_mcf->serverlists.nelts) {
+            ngx_add_timer(&tmp_sc->refresh_timer, random_interval_ms());
+        }
+    }
+
+
+    if (ngx_http_upstream_init_round_robin(&cf, uscf) != NGX_OK) {
+        // see: https://github.com/GUI/nginx-upstream-dynamic-servers/pull/33/files
+        /* if you read the native code you can find out that all you need to do here is ngx_http_upstream_init_round_robin if you don't use other third party modules in the init process,
+            otherwise it may cause memory problem if you use keepalive in the upstream block (it reinitialize the keepalive queue, when remote close the connection 2 TTL later, it will crash)
+        */
         ngx_log_error(NGX_LOG_ERR, log, 0,
             "upstream-serverlist: refresh upstream %V failed, rollback it",
             &uscf->host);
         // cf.pool = sl->pool;
         uscf->servers = old_servers;
-        init(&cf, uscf);
+        // this may not work if old servers do not exist?
+        ngx_http_upstream_init_round_robin(&cf, uscf);
         return -1;
     }
 
@@ -1148,7 +1231,68 @@ refresh_upstream(serverlist *sl, ngx_str_t *body, ngx_log_t *log) {
     }
 #endif
 
-    dump_serverlist(sl);
+    ngx_shm_t shm = {0};
+    shm.size = CACHE_LINE_SIZE * tmp_mcf->serverlists.nelts;
+    shm.log = log;
+    ngx_str_set(&shm.name, "upstream-serverlist-shared-zone");
+    if (ngx_shm_alloc(&shm) != NGX_OK) {
+        return -1;
+    }
+    for (ngx_uint_t i = 0; i < tmp_mcf->serverlists.nelts; i++) {
+        serverlist *temp_sl = (serverlist *)tmp_mcf->serverlists.elts + i;
+        ngx_int_t ret = ngx_shmtx_create(&temp_sl->dump_file_lock,
+            (ngx_shmtx_sh_t *)(shm.addr + CACHE_LINE_SIZE * i), NULL);
+        if ( ret != NGX_OK) {
+            return -1;
+        }
+    }
+
+    dump_serverlist(new_sl);
+
+    serverlist *old_sls = mcf->serverlists.elts;
+
+    for (ngx_uint_t i = 0; i < mcf->serverlists.nelts; i++) {
+
+        if (old_sls[i].pool) {
+            ngx_destroy_pool(old_sls[i].pool);
+            old_sls[i].pool = NULL;
+        }
+
+        if (old_sls[i].new_pool) {
+            ngx_destroy_pool(old_sls[i].new_pool);
+            old_sls[i].new_pool = NULL;
+        }
+    }
+
+    if (old_servers != NULL) {
+        // destry old old_servers
+        ngx_array_destroy(old_servers);
+        old_servers = NULL;
+    }
+
+    if (old_service_conns != NULL) {
+        // destroy old conns
+        ngx_array_destroy(old_service_conns);
+        old_service_conns = NULL;
+    }
+
+    if (old_serverlists != NULL) {
+        // destroy old old_serverlists
+        ngx_array_destroy(old_serverlists);
+        old_serverlists = NULL;
+    }
+
+    if (tmp_mcf->conf_pool_count > 0){
+        //destry previous pool
+        if (tmp_mcf->prev_conf_pool != NULL) {
+            // destry old conf_pool
+            ngx_destroy_pool(tmp_mcf->prev_conf_pool);
+            tmp_mcf->prev_conf_pool = NULL;
+        }
+    }
+    
+    tmp_mcf->prev_conf_pool = mcf->conf_pool;
+    tmp_mcf->conf_pool_count++;
     return 0;
 }
 
@@ -1420,8 +1564,13 @@ recv_from_service(ngx_event_t *ev) {
         // the pool is NULL at first run.
         ngx_destroy_pool(sl->pool);
     }
+
     sl->pool = sl->new_pool;
-    sl->new_pool = NULL;
+
+    if (sl->new_pool != NULL) {
+        ngx_destroy_pool(sl->new_pool);
+        sl->new_pool = NULL;
+    }
 
 exit:
     if (sc->serverlists_curr + 1 >= sc->serverlists_end) {