Hi Bruno,
The skeleton of my code (again, my node application is a reverse web proxy)
is like:
require('spdy').createServer
(
...
var proxy = new httpProxy.HttpProxy({target: {host: ..., port:
...}}); // [1]
proxy.on('proxyError', function(err,req,res) ...);
proxy.proxyRequest(req,res); // [2]
);
It turns out that there is a "proxyError" event emitted in the HttpProxy
constructor call below thanks to a DNS failure for the host of the target
service/application:
var proxy = new httpProxy.HttpProxy({target: {host: ..., port: ...}});
// [1]
i believe my node server crashed thanks to the default error handler so i
just added the listener for "proxyError".
That means the following statement should be skipped completely:
proxy.proxyRequest(req,res); // [2]
if the constructor call (HttpProxy) at [1] fails.
i'll sleep on a good way for error handling in this case.
Thanks again.
On Thursday, December 12, 2013 11:49:34 PM UTC-5, Bruno Fuster wrote:
>
> I have no experience with domains given that's still unstable.
>
> If you use uncaughtException it will fix your problem temporarily: the
> server will not shutdown, this error will not cause any problems for the
> users, but you still have to find it and fix it because something is wrong.
>
> Can you also check that you are not calling res.send() or res.json() or
> res.end() twice?
>
> After you find which endpoint is causing the issue by enabling logs or
> creating some of them you should be able to track it down.
>
> Cheers
>
>
> On Thu, Dec 12, 2013 at 7:17 PM, Hseu-Ming Chen
> <[email protected]<javascript:>
> > wrote:
>
>> Hi Bruno,
>> Thank you for your input.
>>
>>
>> > if (err) { callback(err); }
>> > callback(null,result);
>> > Which causes the callback to be called twice.
>>
>> i searched for similar pattern in my code without finding any
>>
>>
>> > Increase your log level and make sure that you have proper logging
>> > and request/response logging.
>>
>> Yes, i'll ask Winston to be more chatty.
>>
>>
>> > Ps: that error is not a node.js version issue
>>
>> agreed
>>
>> My node.js program is basically a reverse proxy and at the same time a
>> [private|local] CA that authenticates client-side X.509 certs.
>> i'm using http-proxy but i don't think i can conveniently blame the
>> underlying "battle-hardened" http-proxy either.
>>
>>
>> > Ps: use process.on uncaughtException and the server will not crash
>> > Be careful with that :)
>>
>> Instead of
>> process.on('uncaughtException')
>> are you thinking of something like "domain"? i need to read up a bit on
>> it since
>> * it is still "unstable"
>> * unsure whether i can use it in node 0.8.22
>>
>> Thanks again.
>>
>>
>>
>>
>> On Tue, Dec 10, 2013 at 3:57 AM, Bruno Fuster
>> <[email protected]<javascript:>
>> > wrote:
>>
>>> Ps: use process.on uncaughtException and the server will not crash
>>>
>>> Be careful with that :)
>>>
>>> On Dec 9, 2013, at 9:01 PM, ming <[email protected] <javascript:>>
>>> wrote:
>>>
>>> Hi,
>>> i'm running a node application which crashes probably once a week due to
>>> an uncaught "Can't render headers ..." exception. The node.js version in
>>> use is 0.8.22 and the OS distro is RHEL 6.2. i did not find the definitive
>>> pattern of sequence of events which led to the crash though.
>>>
>>> The stack trace looks like:
>>>
>>> http.js:715
>>> throw new Error('Can\'t render headers after they are sent to the
>>> client.'
>>> ^
>>> Error: Can't render headers after they are sent to the client.
>>> at ServerResponse.OutgoingMessage._renderHeaders (http.js:715:11)
>>> at ServerResponse.writeHead (http.js:1059:20)
>>> at Socket.proxyError
>>> (/opt/share/node_modules/http-proxy/lib/node-http-proxy/http-proxy.js:193:9)
>>> at Socket.g (events.js:192:14)
>>> at Socket.EventEmitter.emit (events.js:126:20)
>>> at Socket.connect.require.lookup.addressType (net.js:699:16)
>>> at process.startup.processNextTick.process._tickCallback
>>> (node.js:245:9)
>>>
>>> According to my web surfing, several developers also ran into similar
>>> problem in the past but it is not clear to me what the culprit is. i know
>>> the node.js version i used (0.8.22) has some age but it seems that similar
>>> problems also exist in 0.10.10 so i'm not sure upgrading node.js helps in
>>> this case. Moreover, to upgrade node.js in our environment is somewhat
>>> painful and not really under my control.
>>>
>>> Any suggestion how i can track down and rectify the problem?
>>>
>>> Thanks.
>>>
>>>
>>>
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>>
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>
>
> --
> Bruno Fuster
>
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