[PATCH v4] iproto: report active connections number

[Vladimir Davydov]

On Wed, Feb 27, 2019 at 05:37:57PM +0300, Ilya Kosarev wrote:
> Now there is new member in box.stat.net() called "CONNECTIONS"
> which is a number of active iproto connections.

Please see a few nitpicking comments below.

> 
> Closes #3905
> ---
> https://github.com/tarantool/tarantool/tree/i.kosarev/gh-3905-report-connections-number
> https://github.com/tarantool/tarantool/issues/3905
> 
> Changes in v4:
> - CONNECTIONS counter doesn't have extra lua tables inside anymore
> - refactoring
> 
>  src/box/iproto.cc          |  6 ++++++
>  src/box/iproto.h           |  6 ++++++
>  src/box/lua/stat.c         | 11 +++++++++++
>  test/box/stat_net.result   | 37 +++++++++++++++++++++++++++++++++++++
>  test/box/stat_net.test.lua | 13 +++++++++++++
>  5 files changed, 73 insertions(+)
> 
> diff --git a/src/box/iproto.cc b/src/box/iproto.cc
> index 863eb4f06..d6dafe155 100644
> --- a/src/box/iproto.cc
> +++ b/src/box/iproto.cc
> @@ -2121,6 +2121,12 @@ iproto_mem_used(void)
>  	return slab_cache_used(&net_cord.slabc) + slab_cache_used(&net_slabc);
>  }
>  
> +size_t
> +iproto_connections_n(void)

We don't typically use _n in variable names. Please rename to
iproto_connection_count()

Note, no 's' after 'connection'.

> +{
> +	return mempool_count(&iproto_connection_pool);
> +}
> +
>  void
>  iproto_reset_stat(void)
>  {
> diff --git a/src/box/iproto.h b/src/box/iproto.h
> index 8f3607ffc..0d53d13ed 100644
> --- a/src/box/iproto.h
> +++ b/src/box/iproto.h
> @@ -62,6 +62,12 @@ extern unsigned iproto_readahead;
>  size_t
>  iproto_mem_used(void);
>  
> +/**
> + * Return number of active iproto connections

/**
 * Return the number of active iproto connections.
 */

Note the article and the dot at the end of the comment.
Kostja's fussy about comments purity :-)

> + */
> +size_t
> +iproto_connections_n(void);
> +
>  /**
>   * Reset network statistics.
>   */
> diff --git a/src/box/lua/stat.c b/src/box/lua/stat.c
> index 3fce81f61..f8b9b581e 100644
> --- a/src/box/lua/stat.c
> +++ b/src/box/lua/stat.c
> @@ -52,6 +52,8 @@ extern struct rmean *rmean_error;
>  extern struct rmean *rmean_net;
>  extern struct rmean *rmean_tx_wal_bus;
>  
> +static const char *conn_n_name = "CONNECTIONS";
> +

I don't think there's any point in introducing a variable for this
rather than simply using the string literal directly. There are only
a couple places where we need it, and we aren't going to change those.

>  static void
>  fill_stat_item(struct lua_State *L, int rps, int64_t total)
>  {
> @@ -140,6 +142,10 @@ static int
>  lbox_stat_net_index(struct lua_State *L)
>  {
>  	luaL_checkstring(L, -1);
> +	if (strcmp(conn_n_name, lua_tostring(L, -1)) == 0) {
> +		lua_pushnumber(L, iproto_connections_n());
> +		return 1;
> +	}
>  	return rmean_foreach(rmean_net, seek_stat_item, L);
>  }
>  
> @@ -148,6 +154,11 @@ lbox_stat_net_call(struct lua_State *L)
>  {
>  	lua_newtable(L);
>  	rmean_foreach(rmean_net, set_stat_item, L);
> +
> +	lua_pushstring(L, conn_n_name);
> +	lua_pushnumber(L, iproto_connections_n());
> +	lua_settable(L, -3);
> +
>  	return 1;
>  }