[ZEPPELIN-1028] Fix exported notebook importing error

[AhyoungRyu]

What is this PR for?

This bug seems to be produced by #862. Currently a exported notebook is not imported with below error message.

ERROR [2016-06-20 17:19:21,797] ({qtp559670971-14} NotebookServer.java[onMessage]:231) - Can't handle message
com.google.gson.JsonSyntaxException: 2016-06-20T14:33:31-0700
    at com.google.gson.internal.bind.DateTypeAdapter.deserializeToDate(DateTypeAdapter.java:81)
    at com.google.gson.internal.bind.DateTypeAdapter.read(DateTypeAdapter.java:66)
    at com.google.gson.internal.bind.DateTypeAdapter.read(DateTypeAdapter.java:41)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:93)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:172)
    at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:40)
    at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:81)
    at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:60)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:93)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:172)
    at com.google.gson.Gson.fromJson(Gson.java:791)
    at org.apache.zeppelin.notebook.Notebook.importNote(Notebook.java:199)
    at org.apache.zeppelin.socket.NotebookServer.importNote(NotebookServer.java:656)
    at org.apache.zeppelin.socket.NotebookServer.onMessage(NotebookServer.java:175)
    at org.apache.zeppelin.socket.NotebookSocket.onWebSocketText(NotebookSocket.java:56)
    at org.eclipse.jetty.websocket.common.events.JettyListenerEventDriver.onTextMessage(JettyListenerEventDriver.java:128)
    at org.eclipse.jetty.websocket.common.message.SimpleTextMessage.messageComplete(SimpleTextMessage.java:69)
    at org.eclipse.jetty.websocket.common.events.AbstractEventDriver.appendMessage(AbstractEventDriver.java:65)
    at org.eclipse.jetty.websocket.common.events.JettyListenerEventDriver.onTextFrame(JettyListenerEventDriver.java:122)
    at org.eclipse.jetty.websocket.common.events.AbstractEventDriver.incomingFrame(AbstractEventDriver.java:161)
    at org.eclipse.jetty.websocket.common.WebSocketSession.incomingFrame(WebSocketSession.java:309)
    at org.eclipse.jetty.websocket.common.extensions.ExtensionStack.incomingFrame(ExtensionStack.java:214)
    at org.eclipse.jetty.websocket.common.Parser.notifyFrame(Parser.java:220)
    at org.eclipse.jetty.websocket.common.Parser.parse(Parser.java:258)
    at org.eclipse.jetty.websocket.common.io.AbstractWebSocketConnection.readParse(AbstractWebSocketConnection.java:632)
    at org.eclipse.jetty.websocket.common.io.AbstractWebSocketConnection.onFillable(AbstractWebSocketConnection.java:480)
    at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:544)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:635)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:555)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.text.ParseException: Unparseable date: "2016-06-20T14:33:31-0700"
    at java.text.DateFormat.parse(DateFormat.java:366)
    at com.google.gson.internal.bind.DateTypeAdapter.deserializeToDate(DateTypeAdapter.java:79)

What type of PR is it?

Bug Fix

Todos

What is the Jira issue?

ZEPPELIN-1028

How should this be tested?

1. Apply this patch (Build the source and restart Zeppelin)
2. Export a notebook and try to import it again
3. It should be imported as before

Screenshots (if appropriate)

With this patch, we can import the below two types of date format notebooks.

• Exported after [ZEPPELIN-704] Display elapse time for long running paragraph #862 merged : yyyy-MM-dd'T'HH:mm:ssZ

- Exported before #862 merged : `MMM dd, yyyy HH:mm:ss`

### Questions: - Does the licenses files need update? No - Is there breaking changes for older versions? No - Does this needs documentation? No

[sixmen]

Times in the web interface will show UTC times instead of local times if this patch is applied.

Before applying this patch,

After applying this patch, (I'm at Seoul(+09:00))

I think there are two ways to solve this problem.

First, export a date as natural format (like Jun 21, 2016 2:28:24 AM), and convert UTC to local in web interface.

( modify moment(pdata.dateUpdated).format('MMMM DD YYYY, h:mm:ss A') to moment.utc(pdata.dateUpdated).local().format('MMMM DD YYYY, h:mm:ss A') )

Second, export a date as ISO 8601, and modify importing code.

( modify zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/Notebook.java#importNode 's GsonBuilder to recognize ISO 8601 & natural format )

The second must be support two format (ISO 8601 for exported notebooks from new app and natural format for exported notebooks from old app), so I think first solution is simpler.
But I think standard format(ISO 8601) is preferable for interchange format.

[bzz]

Looks good to me, let's test and merge right after #1043

[AhyoungRyu]

@sixmen Really appreciate for sharing your feedback. I'm in PDT timezone, but I can't reproduce your situation. Here is my case.

• Before applying this patch(latest master branch)

In this case, we can't import the exported notebook because of the date format as we said.

• After applying this patch

I can see my local time in both cases. Am I missing sth ?

[AhyoungRyu]

@bzz Actually I look into #1043, I found that this bug is not related with #1043. So I updated the description of this PR :)

[sixmen]

I'm running the zeppelin server on my server and my server's timezone is UTC.

I think the problem is happened if PC's timezone is different from server's timezone.

[AhyoungRyu]

@sixmen I see, thanks for sharing your problem. Let me check more then :)

[AhyoungRyu]

@sixmen I updated this patch as your second suggestion.

My test server is in KST timezone. As you can see in the above screenshot, displayed elapse time show local time(PDT) as before. And we can also import the exported notebook :)

[sixmen]

This patch is what I thought.
But it may fail to import an exported notebook from old version(e.x 0.5.6).
If you don't mind backward-compatibility, I think this patch is OK.
Otherwise, it may support two date formats.

[AhyoungRyu]

@sixmen Good to hear that :)
IMO it would be better we support only unified date format from now on. And regarding

But it may fail to import an exported notebook from old version(e.x 0.5.6).

I can write down about this to https://zeppelin.apache.org/docs/0.6.0-SNAPSHOT/quickstart/explorezeppelinui.html#home-page so that ppl know. What do you think ?

[corneadoug]

Having backward compatibility and transforming old notebooks into new format would be better.
Adding it to the doc would be a plus, however being sure that nobody end up with issues for now is better.

[AhyoungRyu]

@corneadoug Thank you for sharing your opinion and I agree with you. So I made it to support below two date formats for the backward compatibility.

• Exported after [ZEPPELIN-704] Display elapse time for long running paragraph #862 merged : yyyy-MM-dd'T'HH:mm:ssZ

- Exported before #862 merged : `MMM dd, yyyy HH:mm:ss`

Now we can import both exported .json notebooks which have the above date format.

@sixmen If possible, could you check the updated patch ? :)

[sixmen]

It works well in my test.

[AhyoungRyu]

@sixmen Yeah thanks for clarifying it.

[Leemoonsoo]

LGTM and merge it into master and branch-0.6 if there're no more discussions.