[DISCUSS] Add close() on DataWriter interface

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[DISCUSS] Add close() on DataWriter interface

Jungtaek Lim-2
Hi devs,

I'd like to propose to add close() on DataWriter explicitly, which is the place for resource cleanup.

The rationalization of the proposal is due to the lifecycle of DataWriter. If the scaladoc of DataWriter is correct, the lifecycle of DataWriter instance ends at either commit() or abort(). That makes datasource implementors to feel they can place resource cleanup in both sides, but abort() can be called when commit() fails; so they have to ensure they don't do double-cleanup if cleanup is not idempotent.

I've checked some callers to see whether they can apply "try-catch-finally" to ensure close() is called at the end of lifecycle for DataWriter, and they look like so, but I might be missing something.

What do you think? It would bring backward incompatible change, but given the interface is marked as Evolving and we're making backward incompatible changes in Spark 3.0, so I feel it may not matter.

Would love to hear your thoughts.

Thanks in advance,
Jungtaek Lim (HeartSaVioR)


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Re: [DISCUSS] Add close() on DataWriter interface

cloud0fan
PartitionReader extends Closable, seems reasonable to me to do the same for DataWriter.

On Wed, Dec 11, 2019 at 1:35 PM Jungtaek Lim <[hidden email]> wrote:
Hi devs,

I'd like to propose to add close() on DataWriter explicitly, which is the place for resource cleanup.

The rationalization of the proposal is due to the lifecycle of DataWriter. If the scaladoc of DataWriter is correct, the lifecycle of DataWriter instance ends at either commit() or abort(). That makes datasource implementors to feel they can place resource cleanup in both sides, but abort() can be called when commit() fails; so they have to ensure they don't do double-cleanup if cleanup is not idempotent.

I've checked some callers to see whether they can apply "try-catch-finally" to ensure close() is called at the end of lifecycle for DataWriter, and they look like so, but I might be missing something.

What do you think? It would bring backward incompatible change, but given the interface is marked as Evolving and we're making backward incompatible changes in Spark 3.0, so I feel it may not matter.

Would love to hear your thoughts.

Thanks in advance,
Jungtaek Lim (HeartSaVioR)


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Re: [DISCUSS] Add close() on DataWriter interface

Jungtaek Lim-2
Thanks for the quick response, Wenchen!

I'll leave this thread for early tomorrow so that someone in US timezone can chime in, and craft a patch if no one objects.

On Wed, Dec 11, 2019 at 4:41 PM Wenchen Fan <[hidden email]> wrote:
PartitionReader extends Closable, seems reasonable to me to do the same for DataWriter.

On Wed, Dec 11, 2019 at 1:35 PM Jungtaek Lim <[hidden email]> wrote:
Hi devs,

I'd like to propose to add close() on DataWriter explicitly, which is the place for resource cleanup.

The rationalization of the proposal is due to the lifecycle of DataWriter. If the scaladoc of DataWriter is correct, the lifecycle of DataWriter instance ends at either commit() or abort(). That makes datasource implementors to feel they can place resource cleanup in both sides, but abort() can be called when commit() fails; so they have to ensure they don't do double-cleanup if cleanup is not idempotent.

I've checked some callers to see whether they can apply "try-catch-finally" to ensure close() is called at the end of lifecycle for DataWriter, and they look like so, but I might be missing something.

What do you think? It would bring backward incompatible change, but given the interface is marked as Evolving and we're making backward incompatible changes in Spark 3.0, so I feel it may not matter.

Would love to hear your thoughts.

Thanks in advance,
Jungtaek Lim (HeartSaVioR)


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Re: [DISCUSS] Add close() on DataWriter interface

Ryan Blue
Sounds good to me, too.

On Wed, Dec 11, 2019 at 1:18 AM Jungtaek Lim <[hidden email]> wrote:
Thanks for the quick response, Wenchen!

I'll leave this thread for early tomorrow so that someone in US timezone can chime in, and craft a patch if no one objects.

On Wed, Dec 11, 2019 at 4:41 PM Wenchen Fan <[hidden email]> wrote:
PartitionReader extends Closable, seems reasonable to me to do the same for DataWriter.

On Wed, Dec 11, 2019 at 1:35 PM Jungtaek Lim <[hidden email]> wrote:
Hi devs,

I'd like to propose to add close() on DataWriter explicitly, which is the place for resource cleanup.

The rationalization of the proposal is due to the lifecycle of DataWriter. If the scaladoc of DataWriter is correct, the lifecycle of DataWriter instance ends at either commit() or abort(). That makes datasource implementors to feel they can place resource cleanup in both sides, but abort() can be called when commit() fails; so they have to ensure they don't do double-cleanup if cleanup is not idempotent.

I've checked some callers to see whether they can apply "try-catch-finally" to ensure close() is called at the end of lifecycle for DataWriter, and they look like so, but I might be missing something.

What do you think? It would bring backward incompatible change, but given the interface is marked as Evolving and we're making backward incompatible changes in Spark 3.0, so I feel it may not matter.

Would love to hear your thoughts.

Thanks in advance,
Jungtaek Lim (HeartSaVioR)




--
Ryan Blue
Software Engineer
Netflix
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Re: [DISCUSS] Add close() on DataWriter interface

Nicholas Chammas
In reply to this post by Jungtaek Lim-2
Is this something that would be exposed/relevant to the Python API? Or is this just for people implementing their own Spark data source?

On Wed, Dec 11, 2019 at 12:35 AM Jungtaek Lim <[hidden email]> wrote:
Hi devs,

I'd like to propose to add close() on DataWriter explicitly, which is the place for resource cleanup.

The rationalization of the proposal is due to the lifecycle of DataWriter. If the scaladoc of DataWriter is correct, the lifecycle of DataWriter instance ends at either commit() or abort(). That makes datasource implementors to feel they can place resource cleanup in both sides, but abort() can be called when commit() fails; so they have to ensure they don't do double-cleanup if cleanup is not idempotent.

I've checked some callers to see whether they can apply "try-catch-finally" to ensure close() is called at the end of lifecycle for DataWriter, and they look like so, but I might be missing something.

What do you think? It would bring backward incompatible change, but given the interface is marked as Evolving and we're making backward incompatible changes in Spark 3.0, so I feel it may not matter.

Would love to hear your thoughts.

Thanks in advance,
Jungtaek Lim (HeartSaVioR)


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Re: [DISCUSS] Add close() on DataWriter interface

Jungtaek Lim-2
In reply to this post by Ryan Blue
Nice, thanks for the answer! I'll craft a PR soon. Thanks again.

On Thu, Dec 12, 2019 at 3:32 AM Ryan Blue <[hidden email]> wrote:
Sounds good to me, too.

On Wed, Dec 11, 2019 at 1:18 AM Jungtaek Lim <[hidden email]> wrote:
Thanks for the quick response, Wenchen!

I'll leave this thread for early tomorrow so that someone in US timezone can chime in, and craft a patch if no one objects.

On Wed, Dec 11, 2019 at 4:41 PM Wenchen Fan <[hidden email]> wrote:
PartitionReader extends Closable, seems reasonable to me to do the same for DataWriter.

On Wed, Dec 11, 2019 at 1:35 PM Jungtaek Lim <[hidden email]> wrote:
Hi devs,

I'd like to propose to add close() on DataWriter explicitly, which is the place for resource cleanup.

The rationalization of the proposal is due to the lifecycle of DataWriter. If the scaladoc of DataWriter is correct, the lifecycle of DataWriter instance ends at either commit() or abort(). That makes datasource implementors to feel they can place resource cleanup in both sides, but abort() can be called when commit() fails; so they have to ensure they don't do double-cleanup if cleanup is not idempotent.

I've checked some callers to see whether they can apply "try-catch-finally" to ensure close() is called at the end of lifecycle for DataWriter, and they look like so, but I might be missing something.

What do you think? It would bring backward incompatible change, but given the interface is marked as Evolving and we're making backward incompatible changes in Spark 3.0, so I feel it may not matter.

Would love to hear your thoughts.

Thanks in advance,
Jungtaek Lim (HeartSaVioR)




--
Ryan Blue
Software Engineer
Netflix
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Re: [DISCUSS] Add close() on DataWriter interface

Jungtaek Lim-2
In reply to this post by Nicholas Chammas
> Is this something that would be exposed/relevant to the Python API? Or is this just for people implementing their own Spark data source?

It's latter, and it also helps simplifying built-in data sources as well (as I found the needs while working on https://github.com/apache/spark/pull/26845)

On Thu, Dec 12, 2019 at 3:53 AM Nicholas Chammas <[hidden email]> wrote:
Is this something that would be exposed/relevant to the Python API? Or is this just for people implementing their own Spark data source?

On Wed, Dec 11, 2019 at 12:35 AM Jungtaek Lim <[hidden email]> wrote:
Hi devs,

I'd like to propose to add close() on DataWriter explicitly, which is the place for resource cleanup.

The rationalization of the proposal is due to the lifecycle of DataWriter. If the scaladoc of DataWriter is correct, the lifecycle of DataWriter instance ends at either commit() or abort(). That makes datasource implementors to feel they can place resource cleanup in both sides, but abort() can be called when commit() fails; so they have to ensure they don't do double-cleanup if cleanup is not idempotent.

I've checked some callers to see whether they can apply "try-catch-finally" to ensure close() is called at the end of lifecycle for DataWriter, and they look like so, but I might be missing something.

What do you think? It would bring backward incompatible change, but given the interface is marked as Evolving and we're making backward incompatible changes in Spark 3.0, so I feel it may not matter.

Would love to hear your thoughts.

Thanks in advance,
Jungtaek Lim (HeartSaVioR)