I think the reason is for keeping the original `Function` unchanged, so that existing implemented functions are not affected.
On 2021/07/06 03:34:49 Sijie Guo wrote: > Thank you for starting the discussion! > > I have added this proposal to PIP-86: > https://github.com/apache/pulsar/wiki/PIP-86:-Pulsar-Functions:-Preload-and-release-external-resources > > I have one question: why do you introduce HookFunction? Why not just add > two default methods to the existing Functions API? > > - Sijie > > On Mon, Jul 5, 2021 at 6:49 PM 陈磊 <chen...@cmss.chinamobile.com> wrote: > > > Motivation > > > > It is very useful in many scenarios to provide safe and convenient > > capabilities for function's external resource initialization and release. > > In addition to the normal data processing path, it enables functions to use > > HookFunction to manage external resources > > > > At present, in order to process data, only the logic of resource > > initialization -> processing -> release and shutdown can be written in the > > process() of Function. This method is complicated, insecure, and > > unnecessary. > > > > Instead, we should have a new standard way for users to use Function > > easily and safely. Summarized as follows: > > > > Before Function starts, some resources only need to be initialized once, > > and there is no need to make various judgments in the process() method of > > the Function interface > > > > After closing the Function, in the process of using process(), you need to > > manually close the referenced external resources, which need to be released > > separately in the close() of javaInstance > > API and Implementation Changes > > > > The organization of the function implementation hierarchy has been added, > > it currently looks like the following figure: > > > > Use Cases: > > > > Before transformation > > public class DemoFunction implements Function<String, String>{ > > RedisClient client; > > @Override > > public String process(String str, Context context) { > > 1.client=init(); > > 2.Object object = client.get(key); > > //Data enrichment > > 3.client.close(); > > return null; > > } > > } > > > > After the transformation > > public class DemoFunction implements HookFunction<String, String>{ > > RedisClient client; > > @Override > > public void setup(Context context) { > > Map<String, Object> connectInfo = context.getUserConfigMap(); > > client=init(); > > } > > > > @Override > > public String process(String str, Context context) { > > Object object = client.get(key); > > //Data enrichment > > return null; > > } > > > > @Override > > public void cleanup() { > > client.close(); > > } > > } > > > > It is quite simple and clear to use in function processing code. > > <http://conf.cmss.com/pages/viewpage.action?pageId=140726144> > > > > > > >
