From eec64e440da913cacd0b298e54b4f74e1938068b Mon Sep 17 00:00:00 2001
From: Shawn <506895667@qq.com>
Date: Tue, 16 Feb 2021 14:45:33 +0800
Subject: [PATCH] fix(tracer): create short handler-id if clientid is too long
 (#4164)

* fix(tracer): create short handler-id if clientid is too long

No need to support lists and atoms for when tracing clients/topics.
---
 src/emqx_tracer.erl        | 22 ++++++++++++++++------
 test/emqx_tracer_SUITE.erl |  4 ++--
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/src/emqx_tracer.erl b/src/emqx_tracer.erl
index a01dcb27f..365336f03 100644
--- a/src/emqx_tracer.erl
+++ b/src/emqx_tracer.erl
@@ -28,7 +28,7 @@
         , stop_trace/1
         ]).
 
--type(trace_who() :: {clientid | topic, binary() | list()}).
+-type(trace_who() :: {clientid | topic, binary()}).
 
 -define(TRACER, ?MODULE).
 -define(FORMAT, {emqx_logger_formatter,
@@ -135,9 +135,9 @@ filter_traces(#{id := Id, level := Level, dst := Dst}, Acc) ->
     end.
 
 handler_id(?TOPIC_TRACE(Topic)) ->
-    list_to_atom(?TOPIC_TRACE_ID(str(Topic)));
+    list_to_atom(?TOPIC_TRACE_ID(handler_name(Topic)));
 handler_id(?CLIENT_TRACE(ClientId)) ->
-    list_to_atom(?CLIENT_TRACE_ID(str(ClientId))).
+    list_to_atom(?CLIENT_TRACE_ID(handler_name(ClientId))).
 
 filter_by_meta_key(#{meta:=Meta}=LogEvent, {MetaKey, MetaValue}) ->
     case maps:find(MetaKey, Meta) of
@@ -150,6 +150,16 @@ filter_by_meta_key(#{meta:=Meta}=LogEvent, {MetaKey, MetaValue}) ->
         _ -> ignore
     end.
 
-str(Bin) when is_binary(Bin) -> binary_to_list(Bin);
-str(Atom) when is_atom(Atom) -> atom_to_list(Atom);
-str(Str) when is_list(Str) -> Str.
+handler_name(Bin) ->
+    case byte_size(Bin) of
+        Size when Size =< 200 -> binary_to_list(Bin);
+        _ -> hashstr(Bin)
+    end.
+
+hashstr(Bin) ->
+    hexstr(crypto:hash(sha, Bin)).
+
+hexstr(Bin) ->
+    lists:flatten(
+        [io_lib:format("~2.16.0B", [Int])
+         || Int <- binary_to_list(Bin)]).
diff --git a/test/emqx_tracer_SUITE.erl b/test/emqx_tracer_SUITE.erl
index c3b4ea8f1..94bac7e3d 100644
--- a/test/emqx_tracer_SUITE.erl
+++ b/test/emqx_tracer_SUITE.erl
@@ -47,8 +47,8 @@ t_start_traces(_Config) ->
     {error, _} = emqx_tracer:start_trace({clientid, <<"client">>}, debug, "tmp/client.log"),
     emqx_logger:set_log_level(debug),
     ok = emqx_tracer:start_trace({clientid, <<"client">>}, debug, "tmp/client.log"),
-    ok = emqx_tracer:start_trace({clientid, "client2"}, all, "tmp/client2.log"),
-    ok = emqx_tracer:start_trace({clientid, client3}, all, "tmp/client3.log"),
+    ok = emqx_tracer:start_trace({clientid, <<"client2">>}, all, "tmp/client2.log"),
+    ok = emqx_tracer:start_trace({clientid, <<"client3">>}, all, "tmp/client3.log"),
     {error, {invalid_log_level, bad_level}} = emqx_tracer:start_trace({clientid, <<"client4">>}, bad_level, "tmp/client4.log"),
     {error, {handler_not_added, {file_error,".",eisdir}}} = emqx_tracer:start_trace({clientid, <<"client5">>}, debug, "."),
     ok = emqx_tracer:start_trace({topic, <<"a/#">>}, all, "tmp/topic_trace.log"),