Do we need to drain a closed channel ?

[Shubha Acharya]

Hey,

I have been working with buffered channels. I have stumbled upon a scenario where buffered channel will be closed and the receivers of the channel terminates before consuming all the elements in the buffer. So my question is will there be any issue regarding Garbage Collection of channel which eventually leads to memory or resource leaks because of the left out items in the buffer? or any other concerns that I must be aware of?

[Ian Lance Taylor]

On Fri, Mar 1, 2024 at 6:26 AM Shubha Acharya
<shubhaac...@gmail.com> wrote:
>
> I have been working with buffered channels. I have stumbled upon a scenario where buffered channel will be closed and the receivers of the channel terminates before consuming all the elements in the buffer. So my question is will there be any issue regarding Garbage Collection of channel which eventually leads to memory or resource leaks because of the left out items in the buffer? or any other concerns that I must be aware of?

No more than, say, a slice. An unreferenced channel will be garbage
collected, which will remove references to any objects in the channel
buffer. If those objects have no other references, they too will be
garbage collected.

Ian

[Bosung Park]

I understand that unreferenced channels will eventually be garbage collected, along with any objects in their buffer. 

So, it is not actually memory leak.

However, I am curious if there is a possibility that, until the garbage collection occurs, 

the accumulation of unnecessary memory could appear as a memory leak during monitoring?

Or, garbage collection occurs occurs immediately, that there is no possibility that the accumulation of unnecessary memory could appear during monitoring?

[Ian Lance Taylor]

On Mon, Nov 11, 2024 at 9:02 AM Bosung Park <bosun...@tryalign.ai> wrote:
>
> I understand that unreferenced channels will eventually be garbage collected, along with any objects in their buffer.
> So, it is not actually memory leak.
>
> However, I am curious if there is a possibility that, until the garbage collection occurs,
> the accumulation of unnecessary memory could appear as a memory leak during monitoring?
>
> Or, garbage collection occurs occurs immediately, that there is no possibility that the accumulation of unnecessary memory could appear during monitoring?

An unreferenced channel will not be collected immediately. This is no
different from an unreferenced slice, or any other type. This delay
is something to consider when monitoring memory usage. That is true
for all types, and there is nothing special about channels in this
regard.

Ian

> On Friday, March 1, 2024 at 11:34:55 PM UTC+9 Ian Lance Taylor wrote:
>>
>> On Fri, Mar 1, 2024 at 6:26 AM Shubha Acharya
>> <shubhaac...@gmail.com> wrote:
>> >
>> > I have been working with buffered channels. I have stumbled upon a scenario where buffered channel will be closed and the receivers of the channel terminates before consuming all the elements in the buffer. So my question is will there be any issue regarding Garbage Collection of channel which eventually leads to memory or resource leaks because of the left out items in the buffer? or any other concerns that I must be aware of?
>>
>> No more than, say, a slice. An unreferenced channel will be garbage
>> collected, which will remove references to any objects in the channel
>> buffer. If those objects have no other references, they too will be
>> garbage collected.
>>
>> Ian
>

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[Henry]

Hi all,

I have been wondering about this as well. Let's say there is a channel, and the sender runs in a separate goroutine:
```

// sender

go func() {

      for _, data := range output() {

             ch <- data

      }

}()

```

Now the channel isn't consumed. Perhaps, it is a part of the following function:
```

func ExecuteCommand(command string) (output <- chan string, err error)

// and the client executes the function without needing the output

if _, err := ExecuteCommand(cmd); err!=nil{

   ...

}

``` 
Does the channel need to be drained? My thinking is that if it isn't drained, the sender goroutine will wait forever and the goroutine will leak. The channel will not be garbage collected because the goroutine is still running. What do you think?

Thanks.

Henry

[Robert Engels]

Yes you need to manage your producers and consumers. Think about it more deeply - given your scenario what would you want to happen? Is that universal - probably not. 

On Nov 24, 2024, at 10:13 PM, Henry <henry.ad...@gmail.com> wrote:

Hi all,

To view this discussion visit https://groups.google.com/d/msgid/golang-nuts/7ad5a126-87ab-4c33-afc6-6c537dafe3aan%40googlegroups.com.