src/hz.erl

@@ -9,7 +9,7 @@
 %%%
 %%% The get/set admin functions are for setting or checking things like the Gajumaru
 %%% "network ID" and list of addresses of nodes you want to use for answering
-%%% queries to the blockchain.
+%%% queries to the blockchain. Get functions are arity 0, and set functions are arity 1.
 %%%
 %%% The JSON query interface functions are the blockchain query functions themselves
 %%% which are translated to network queries and return Erlang messages as responses.
@@ -18,8 +18,8 @@
 %%% a desired call to a smart contract on the chain to call data serialized in a form
 %%% that a Gajumaru compatible wallet or library can sign and submit to a Gajumaru node.
 %%%
-%%% This module does not implement the OTP application behavior.
+%%% NOTE:
-%%% helper functions.
+%%% This module does not implement the OTP application behavior. Refer to hakuzaru.erl.
 %%% @end
 
 -module(hz).
@@ -225,7 +225,7 @@
          NetworkID :: string(),
          Reason    :: term().
 %% @doc
-%% Returns the network ID or the atom `none' if it is unset.
+%% Returns the network ID or the atom `none' if unavailable.
 %% Checking this is not normally necessary, but if network ID assignment is dynamic
 %% in your system it may be necessary to call this before attempting to form
 %% call data or perform other actions on chain that require a signature.
@@ -241,7 +241,9 @@ network_id() ->
 %% @doc
 %% Returns the list of currently assigned nodes.
 %% The normal reason to call this is in preparation for altering the nodes list or
-%% checking the current list in debugging.
+%% checking the current list in debugging. Note that the first node in the list is
+%% the "sticky" node: the one that will be used for submitting transactions and
+%% querying `next_nonce'.
 
 chain_nodes() ->
     hz_man:chain_nodes().
@@ -251,19 +253,26 @@ chain_nodes() ->
     when List   :: [chain_node()],
          Reason :: {invalid, [term()]}.
 %% @doc
-%% Sets the nodes that are intended to be used as your interface to the peer
+%% Sets the chain nodes that will be queried whenever you communicate with the chain.
-%% network. The common situation is that your project runs a non-mining node as
-%% part of your backend infrastructure. Typically one or two nodes is plenty, but
-%% this may need to expand depending on how much query load your application generates.
-%% The Hakuzaru manager will load balance by round-robin distribution.
 %%
-%% NOTE: When load balancing in this way be aware that there can be race conditions
+%% The common situation is that a project runs a non-mining node as part of the backend
-%% among the backend nodes with regard to a single account's current nonce when performing
+%% infrastructure. Typically one or two nodes is plenty, but this may need to expand
-%% contract calls in quick succession. Round robin distribution is extremely useful when
+%% depending on how much query load your application generates.
-%% performing rapid lookups to the chain, but does not work well when submitting many
+%%
-%% transactions to the chain from a single user in a short period of time. A future version
+%% There are two situations: one node, or multiple nodes.
-%% of this library will allow the caller to designate a single node as "sticky" to be used
+%%
-%% exclusively in the case of nonce reads and TX submissions.
+%% Single node:
+%% In the case of a single node, everything passes through that one node. Duh.
+%%
+%% Multiple nodes:
+%% In the case of multiple nodes a distinction is made between the node to which
+%% transactions that update the chain state are made and to which `next_nonce' queries
+%% are made, and nodes that are used for read-only queries. The node to which stateful
+%% transactions are submitted is called the "sticky node". This is the first node
+%% (head position) in the list of nodes submitted to the chain when `chain_nodes/1'
+%% is called. If using multiple nodes but the sticky node should also be used for
+%% read-only queries, submit the sticky node at the head of the list and again in
+%% the tail.
 
 chain_nodes(List) when is_list(List) ->
     hz_man:chain_nodes(List).
@@ -271,7 +280,16 @@ chain_nodes(List) when is_list(List) ->
 
 -spec tls() -> boolean().
 %% @doc
-%% Check whether TLS is in use.
+%% Check whether TLS is in use. The typical situation is to not use TLS as nodes that
+%% serve as part of the backend of an application are typically run in the same
+%% backend network as the application service. When accessing chain nodes over the WAN
+%% however, TLS is strongly recommended to avoid a MITM attack.
+%%
+%% In this version of Hakuzaru TLS is either on or off for all nodes, making a mixed
+%% infrastructure complicated to support without two Hakuzaru instances. This will
+%% likely become a per-node setting in the future.
+%%
+%% TLS defaults to `false'.
 
 tls() ->
     hz_man:tls().
@@ -281,6 +299,8 @@ tls() ->
 %% @doc
 %% Set TLS true or false. That's what a boolean is, by the way, `true' or `false'.
 %% This is a condescending comment. That means I am talking down to you.
+%%
+%% TLS defaults to `false'.
 
 tls(Boolean) ->
     hz_man:tls(Boolean).
@@ -291,6 +311,8 @@ tls(Boolean) ->
     when Timeout :: pos_integer() | infinity.
 %% @doc
 %% Returns the current request timeout setting in milliseconds.
+%% The default timeout is 5,000ms.
+%% The max timeout is 120,000ms.
 
 timeout() ->
     hz_man:timeout().
@@ -300,6 +322,8 @@ timeout() ->
     when MS :: pos_integer() | infinity.
 %% @doc
 %% Sets the request timeout in milliseconds.
+%% The default timeout is 5,000ms.
+%% The max timeout is 120,000ms.
 
 timeout(MS) ->
     hz_man:timeout(MS).
@@ -576,18 +600,18 @@ acc_pending_txs(AccountID) ->
 %% Retrieve the next nonce for the given account
 
 next_nonce(AccountID) ->
-%   case request(["/v3/accounts/", AccountID, "/next-nonce"]) of
+    case request_sticky(["/v3/accounts/", AccountID, "/next-nonce"]) of
-%       {ok, #{"next_nonce" := Nonce}}           -> {ok, Nonce};
+        {ok, #{"next_nonce" := Nonce}}           -> {ok, Nonce};
-%       {ok, #{"reason" := "Account not found"}} -> {ok, 1};
-%       {ok, #{"reason" := Reason}}              -> {error, Reason};
-%       Error                                    -> Error
-%   end.
-    case request(["/v3/accounts/", AccountID]) of
-        {ok, #{"nonce"  := Nonce}}               -> {ok, Nonce + 1};
         {ok, #{"reason" := "Account not found"}} -> {ok, 1};
         {ok, #{"reason" := Reason}}              -> {error, Reason};
         Error                                    -> Error
     end.
+%   case request_sticky(["/v3/accounts/", AccountID]) of
+%       {ok, #{"nonce"  := Nonce}}               -> {ok, Nonce + 1};
+%       {ok, #{"reason" := "Account not found"}} -> {ok, 1};
+%       {ok, #{"reason" := Reason}}              -> {error, Reason};
+%       Error                                    -> Error
+%   end.
 
 
 -spec dry_run(TX) -> {ok, Result} | {error, Reason}
@@ -729,7 +753,7 @@ tx_info(ID) ->
 
 post_tx(Data) when is_binary(Data) ->
     JSON = zj:binary_encode(#{tx => Data}),
-    request("/v3/transactions", JSON);
+    request_sticky("/v3/transactions", JSON);
 post_tx(Data) when is_list(Data) ->
     post_tx(list_to_binary(Data)).
 
@@ -841,6 +865,14 @@ status_chainends() ->
     request("/v3/status/chain-ends").
 
 
+request_sticky(Path) ->
+    hz_man:request_sticky(unicode:characters_to_list(Path)).
+
+
+request_sticky(Path, Payload) ->
+    hz_man:request_sticky(unicode:characters_to_list(Path), Payload).
+
+
 request(Path) ->
     hz_man:request(unicode:characters_to_list(Path)).
 

src/hz_fetcher.erl

@@ -4,7 +4,7 @@
 -copyright("Craig Everett <ceverett@tsuriai.jp>").
 -license("MIT").
 
--export([connect/4, slowly_connect/4]).
+-export([connect/4, connect_slowly/4]).
 
 
 connect(Node = {Host, Port}, Request, From, Timeout) ->
@@ -206,7 +206,7 @@ read_hval(_, Received, _, _, _) ->
     {error, headers}.
 
 
-slowly_connect(Node, {get, Path}, From, Timeout) ->
+connect_slowly(Node, {get, Path}, From, Timeout) ->
     HttpOptions = [{connect_timeout, 3000}, {timeout, Timeout}],
     URL = lists:flatten(url(Node, Path)),
     Request = {URL, []},
@@ -217,7 +217,7 @@ slowly_connect(Node, {get, Path}, From, Timeout) ->
             BAD                          -> {error, BAD}
         end,
     gen_server:reply(From, Result);
-slowly_connect(Node, {post, Path, Payload}, From, Timeout) ->
+connect_slowly(Node, {post, Path, Payload}, From, Timeout) ->
     HttpOptions = [{connect_timeout, 3000}, {timeout, Timeout}],
     URL = lists:flatten(url(Node, Path)),
     Request = {URL, [], "application/json", Payload},

src/hz_man.erl

@@ -21,7 +21,7 @@
          timeout/0,     timeout/1]).
 
 %% The whole point of this module:
--export([request/1, request/2]).
+-export([request_sticky/1, request_sticky/2, request/1, request/2]).
 
 %% gen_server goo
 -export([start_link/0]).
@@ -40,11 +40,11 @@
          req  = none :: none | binary()}).
 
 -record(s,
-        {tls         = false        :: boolean(),
+        {tls         = false    :: boolean(),
-         chain_nodes = {[], []}     :: {[hz:chain_node()], [hz:chain_node()]},
+         chain_nodes = {[], []} :: {[hz:chain_node()], [hz:chain_node()]},
-         sticky      = none         :: none | hz:chain_node(),
+         sticky      = none     :: none | hz:chain_node(),
-         fetchers    = []           :: [#fetcher{}],
+         fetchers    = []       :: [#fetcher{}],
-         timeout     = 5000         :: pos_integer()}).
+         timeout     = 5000     :: pos_integer()}).
 
 
 -type state()   :: #s{}.
@@ -94,6 +94,25 @@ timeout(Value) when 0 < Value, Value =< 120000 ->
     gen_server:cast(?MODULE, {timeout, Value}).
 
 
+-spec request_sticky(Path) -> {ok, Value} | {error, Reason}
+    when Path   :: unicode:charlist(),
+         Value  :: map(),
+         Reason :: hz:chain_error().
+
+request_sticky(Path) ->
+    gen_server:call(?MODULE, {request_sticky, {get, Path}}, infinity).
+
+
+-spec request_sticky(Path, Data) -> {ok, Value} | {error, Reason}
+    when Path   :: unicode:charlist(),
+         Data   :: unicode:charlist(),
+         Value  :: map(),
+         Reason :: hz:chain_error().
+
+request_sticky(Path, Data) ->
+    gen_server:call(?MODULE, {request_sticky, {post, Path, Data}}, infinity).
+
+
 -spec request(Path) -> {ok, Value} | {error, Reason}
     when Path   :: unicode:charlist(),
          Value  :: map(),
@@ -145,10 +164,13 @@ init(none) ->
 handle_call({request, Request}, From, State) ->
     NewState = do_request(Request, From, State),
     {noreply, NewState};
+handle_call({request_sticky, Request}, From, State) ->
+    NewState = do_request_sticky(Request, From, State),
+    {noreply, NewState};
 handle_call(tls, _, State = #s{tls = TLS}) ->
     {reply, TLS, State};
-handle_call(chain_nodes, _, State = #s{chain_nodes = {Wait, Used}}) ->
+handle_call(chain_nodes, _, State) ->
-    Nodes = lists:append(Wait, Used),
+    Nodes = do_chain_nodes(State),
     {reply, Nodes, State};
 handle_call(timeout, _, State = #s{timeout = Value}) ->
     {reply, Value, State};
@@ -160,10 +182,9 @@ handle_call(Unexpected, From, State) ->
 handle_cast({tls, Boolean}, State) ->
     NewState = do_tls(Boolean, State),
     {noreply, NewState};
-handle_cast({chain_nodes, []}, State) ->
+handle_cast({chain_nodes, List}, State) ->
-    {noreply, State#s{chain_nodes = {[], []}}};
+    NewState = do_chain_nodes(List, State),
-handle_cast({chain_nodes, ToUse}, State) ->
+    {noreply, NewState};
-    {noreply, State#s{chain_nodes = {ToUse, []}}};
 handle_cast({timeout, Value}, State) ->
     {noreply, State#s{timeout = Value}};
 handle_cast(Unexpected, State) ->
@@ -218,6 +239,23 @@ terminate(_, _) ->
 
 %%% Doer Functions
 
+do_chain_nodes(#s{sticky = none, chain_nodes = {Wait, Used}}) ->
+    lists:append(Wait, Used);
+do_chain_nodes(#s{sticky = Sticky, chain_nodes = {Wait, Used}}) ->
+    case lists:append(Wait, Used) of
+        [Sticky] -> [Sticky];
+        Nodes    -> [Sticky | Nodes]
+    end.
+
+
+do_chain_nodes([], State) ->
+    State#s{sticky = none, chain_nodes = {[], []}};
+do_chain_nodes(List = [Sticky], State) ->
+    State#s{sticky = Sticky, chain_nodes = {List, []}};
+do_chain_nodes([Sticky | List], State) ->
+    State#s{sticky = Sticky, chain_nodes = {List, []}}.
+
+
 do_tls(true, State) ->
     ok = ssl:start(),
     State#s{tls = true};
@@ -227,17 +265,21 @@ do_tls(_, State) ->
     State.
 
 
-do_request(_, From, State = #s{chain_nodes = {[], []}}) ->
+do_request_sticky(_, From, State = #s{sticky = none}) ->
     ok = gen_server:reply(From, {error, no_nodes}),
     State;
-do_request(Request,
+do_request_sticky(Request,
-           From,
+                  From,
-           State = #s{tls         = false,
+                  State = #s{tls       = TLS,
-                      fetchers    = Fetchers,
+                             fetchers  = Fetchers,
-                      chain_nodes = {[Node | Rest], Used},
+                             sticky    = Node,
-                      timeout     = Timeout}) ->
+                             timeout   = Timeout}) ->
     Now = erlang:system_time(nanosecond),
-    Fetcher = fun() -> hz_fetcher:connect(Node, Request, From, Timeout) end,
+    Fetcher =
+        case TLS of
+            true  -> fun() -> hz_fetcher:connect_slowly(Node, Request, From, Timeout) end;
+            false -> fun() -> hz_fetcher:connect(Node, Request, From, Timeout) end
+        end,
     {PID, Mon} = spawn_monitor(Fetcher),
     New = #fetcher{pid  = PID,
                    mon  = Mon,
@@ -245,15 +287,24 @@ do_request(Request,
                    node = Node,
                    from = From,
                    req  = Request},
-    State#s{fetchers = [New | Fetchers], chain_nodes = {Rest, [Node | Used]}};
+    State#s{fetchers = [New | Fetchers]}.
+
+
+do_request(_, From, State = #s{chain_nodes = {[], []}}) ->
+    ok = gen_server:reply(From, {error, no_nodes}),
+    State;
 do_request(Request,
            From,
-           State = #s{tls         = true,
+           State = #s{tls         = TLS,
                       fetchers    = Fetchers,
                       chain_nodes = {[Node | Rest], Used},
                       timeout     = Timeout}) ->
     Now = erlang:system_time(nanosecond),
-    Fetcher = fun() -> hz_fetcher:slowly_connect(Node, Request, From, Timeout) end,
+    Fetcher =
+        case TLS of
+            true  -> fun() -> hz_fetcher:connect_slowly(Node, Request, From, Timeout) end;
+            false -> fun() -> hz_fetcher:connect(Node, Request, From, Timeout) end
+        end,
     {PID, Mon} = spawn_monitor(Fetcher),
     New = #fetcher{pid  = PID,
                    mon  = Mon,