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https://issues.apache.org/jira/browse/HDFS-11712?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15988212#comment-15988212
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Yiqun Lin edited comment on HDFS-11712 at 4/28/17 5:09 AM:
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Thanks [~anu] for taking a look!
{quote}
Do you think we can use ObjectReader or ObjectWriter in many places instead of
ObjectMapper ?
{quote}
Yes, that's also what I want to do in the new patch.
{{ObjectMapper}} is a heavy-weight object, but {{ObjectReader}} and
{{ObjectWriter}} are light-weight instances and they are fully thread-safe,
reusable.
In the updated patch, I am mainly doing these three things:
* If the instance {{ObjectMapper}}, {{ObjectReader}} or {{ObjectWriter}}
configured is complete the same, I will put that instance into the Utility
class {{JsonUtils}}. It's safe to do this since {{ObjectMapper}} or other
related instances are thread safe as long as we have configured instances
before use and not changed the configuration later.
* If not, I am creating the instance in their all classes respectively and
reuse the instance in their own class.
* Upgrade all {{ObjectMapper}} APIs used in ozone, API version changed from
jackson1 to jackson2.
Attach the new patch. Patch seems a little big but actually the change is
minor, just a few codes being updated and it will not take a long time to
review, :).
was (Author: linyiqun):
Thanks [~anu] for taking a look!
{quote}
Do you think we can use ObjectReader or ObjectWriter in many places instead of
ObjectMapper ?
{quote}
Yes, that's also what I want to do in the new patch.
{{ObjectMapper}} is a heavy-weight object, but {{ObjectReader}} and
{{ObjectWriter}} are light-weight instances and they are fully thread-safe,
reusable.
In the updated patch, I am mainly doing these three things:
* If the instance {{ObjectMapper}}, {{ObjectReader}} or {{ObjectWriter}}
confgigured is complete the same, I will put that instance into the Utility
class {{JsonUtils}}. It's safe to do this since {{ObjectMapper}} or other
related instances are thread safe as long as we have configured instances
before use and not changed the configuration later.
* If not, I am creating the instance in there all classes respectively and
reuse the instance in their own class.
* Upgrade all {{ObjectMapper}} APIs used in ozone, API version changed from
jackson1 to jackson2.
Attach the new patch. Patch seems a little big but actually the change is
minor, just a few codes being updated and it will not take a long time to
review, :).
> Ozone: Reuse ObjectMapper instance to improve the performance
> -------------------------------------------------------------
>
> Key: HDFS-11712
> URL: https://issues.apache.org/jira/browse/HDFS-11712
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ozone
> Affects Versions: HDFS-7240
> Reporter: Yiqun Lin
> Assignee: Yiqun Lin
> Attachments: HDFS-11712-HDFS-7240.001.patch,
> HDFS-11712-HDFS-7240.002.patch
>
>
> In the ozone, there are many places using {{ObjectMapper}} to do the
> object-json transformation. From the page of {{ObjectMapper}}
> (https://github.com/FasterXML/jackson-docs/wiki/Presentation:-Jackson-Performance),
> {{ObjectMapper}} is a heavy-weight object, it not a good bevahiour to
> create this instance everywhere.
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