TypeError: Cannot read property 'write' of null at Zlib.callback (zlib.js:499:33) for Nodejs 14.5

[naren0021]

I have recently experienced the issue on node 14.x on the production

uncaughtException: Cannot read property 'write' of null
TypeError: Cannot read property 'write' of null
    at Zlib.callback (zlib.js:499:33)

[Ayase-252]

Could you provide a minimal repro? Can you reproduce this in latest LTS v14.17 or Current v16.3?

[aduh95]

Hi @naren0021, from what I can see of the error stack you copied (BTW, it's usually better to copy the whole output if you want someone to help you to have the correct info), it seems you have a module called zlib.js which has a bug on line 499: it tries to read a property of an object which is in fact null. It should look something like that:

   myObject.write('data');

It either means that you need to add a check before trying to call the method:

  if (myObject != null) myObject.write('data');

Or that there's somewhere else in your app, in which case there's not much I can do to help you...

I see in the issue title that you are using Node.js 14.5, kindly consider upgrading to the latest version, lots of bugs are fixed simply by keeping up-to-date with the tools you're using.

[naren0021]

correct error is this @Ayase-252

     at Zlib.callback (zlib.js:499:33)
    TypeError: Cannot read property 'write' of null
    at Zlib.callback (zlib.js:499:33)
   TypeError: Cannot read property 'write' of null
    at Zlib.callback (zlib.js:499:33)
   TypeError: Cannot read property 'write' of null
   at Zlib.callback (zlib.js:499:33)
   TypeError: Cannot read property 'write' of null
   at Zlib.callback (zlib.js:499:33)
   TypeError: Cannot read property 'write' of null
   at Zlib.callback (zlib.js:499:33)
   TypeError: Cannot read property 'write' of null
   at Zlib.callback (zlib.js:499:33)
   TypeError: Cannot read property 'write' of null
   at Zlib.callback (zlib.js:499:33)

yes sure I will update the Node version and will update you @aduh95

[bl-ue]

@aduh95 this looks like a case of nodejs/node#36421 :(

[KRAUS1203]

This issue is not as simple as since Zlib is a submodule of core node js and is used internally when web sockets are used. so if we write something on websocket i.e. socket.emit we dont have access to zlib. so cannot do the check mentioned by @aduh95 .
also this is when socket connection is closed by client side while server is writing something.

[aduh95]

@KRAUS1203 I didn't realize zlib.js was referring to a core module, thanks for pointing it out – stack traces in Node.js v15+ would refer to it as node:zlib to remove the ambiguity, I forgot v14.x still has the old style ones.

Line 499 of zlib.js is an empty line in v14.5.0: https://github.com/nodejs/node/blob/v14.5.0/lib/zlib.js#L499
@naren0021 are you using a modified version of Node.js?

[bl-ue]

@naren0021 are you using a modified version of Node.js?

I wouldn't think so — you can see in nodejs/node#36421 that three different people have the same line (499).

[bl-ue]

That looks like node 8 actually https://github.com/nodejs/node/blob/v8.x/lib/zlib.js#L499❓

[bl-ue]

@naren0021 you said:

on node 14.x on the production

but this appears to be like @KRAUS1203's problem, and in nodejs/node#36421 they said that they were using 8.9.4 🤔

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If you need further assistance or have questions, you can also search for similar issues on Stack Overflow.
Make sure to look at the README file for the most updated links.