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No error logging on coroutine.resume (pull-request for issue #951) #952

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No error logging on coroutine.resume (pull-request for issue #951) #952

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3da880a
Pull-request for issue #951
bungle Jan 12, 2017
650b81a
Fixing Travis tests on PR #952
bungle Jan 12, 2017
7ede2ea
Fixed tests count for PR #952
bungle Jan 12, 2017
23189a0
Fixed coroutine tests on PR #952
bungle Jan 15, 2017
3e1d561
Fixed coroutine test #10 on PR #952
bungle Jan 15, 2017
f4d07dd
Made coroutine test #10 to test error message on PR #952
bungle Jan 15, 2017
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3 changes: 0 additions & 3 deletions src/ngx_http_lua_util.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1437,9 +1437,6 @@ ngx_http_lua_run_thread(lua_State *L, ngx_http_request_t *r,

ctx->cur_co_ctx = next_coctx;

ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
"lua coroutine: %s: %s\n%s", err, msg, trace);

/* try resuming on the new coroutine again */
continue;
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As I mentioned earlier, should we just lower the log level here? Like info?

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@bungle bungle Jan 15, 2017 •
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If we do so, this will be different than what Lua / LuaJIT does. They don't write anything. I mean, OpenResty doesn't log anything when wrapping code with pcall. If you want to log errors even when they are raised in a code wrapped with pcall, then I would consider having this logged as well, and of course we need to change pcall then as well. This would differ from what users' expect, though. My only concern is that I'm not sure if that removed log entry removes error logging also from some case where it shouldn't. That's why I asked do anyone of you know if it is only handling when users' code calls coroutine.resume (that's the only place where this logging should be silenced).

But I probably wouldn't worry too much if this is lowered to INFO or even DEBUG. Some library writers can rely on this, e.g. exiting coroutines with error and then handling the errors themselves. If this means that the logs will be filled with these messages, then that could be a problem. E.g. my routing library is relying on coroutines and it will by default log the errors from coroutine.resume, so this would mean that errors are logged twice.

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@bungle pcall is a more explicit try/catch in the Lua world while many Lua programmers may overlook the error handling in coroutine.resume.

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@agentzh, I agree, but that's how the Lua is. Those that use coroutine.resume should know that it is effectively a pcall. There is some history to this as pcall has not been fully compatible with coroutines (http://lua-users.org/wiki/PcallAndCoroutines).

}
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13 changes: 6 additions & 7 deletions t/091-coroutine.t
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Expand Up @@ -4,7 +4,7 @@ use Test::Nginx::Socket::Lua;

repeat_each(2);

plan tests => repeat_each() * (blocks() * 3 + 5);
plan tests => repeat_each() * blocks() * 3 + 4;
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Better keep the parens otherwise we need to update this plan every time we change the repeat_each number. Also, the repeat each number is automatically increased on the "check leak" test mode of Test::Nginx::Socket, and your change will break the test plan in that test mode.


$ENV{TEST_NGINX_RESOLVER} ||= '8.8.8.8';

Expand Down Expand Up @@ -281,7 +281,7 @@ GET /lua
end)
end

N = 10
N = 10
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Better avoid unrelated changes to make your changeset atomic. It's better for version control.

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@bungle bungle Jan 14, 2017 •
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I think my editor did it automatically. I will add that space back.

x = gen(N) -- generate primes up to N
while 1 do
local n = x() -- pick a number until done
Expand Down Expand Up @@ -483,8 +483,8 @@ done
GET /lua
--- response_body
hello
--- error_log eval
["stack traceback:", "coroutine 0:", "coroutine 1:", "coroutine 2:"]
--- no_error_log
[error]
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Hmm, the indentation of this test case is to test the Lua land backtrace. After your change, we no longer have any tests designed for this purpose.

I'm not sure if silencing the error logging is a good idea. Maybe we can make it a lower log level like "warn" or even "info"?

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Also, better check the return values of coroutine.resume for better test coverage.

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coroutine.resume is a pcall and its purpose is to catch the errors aka silence the errors and let users handle them. I will make that test better so it checks the return value.




Expand Down Expand Up @@ -901,8 +901,8 @@ qr/^child: resume: falsecontent_by_lua\(nginx\.conf:\d+\):4: bad
child: status: dead
parent: status: running
$/s
--- error_log eval
qr/lua coroutine: runtime error: content_by_lua\(nginx\.conf:\d+\):4: bad/
--- no_error_log
[error]



Expand Down Expand Up @@ -1315,4 +1315,3 @@ co yield: 2

--- no_error_log
[error]