[MGNLUI-3339] Vaadin "Communication Problem" error message on slow connections Created: 02/Feb/15  Updated: 09/Mar/21  Resolved: 02/Aug/15

Status: Closed
Project: Magnolia UI
Component/s: admincentral
Affects Version/s: 5.3.6
Fix Version/s: 5.4

Type: Bug Priority: Major
Reporter: Will Scheidegger Assignee: Unassigned
Resolution: Fixed Votes: 3
Labels: OnDemand, support
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Attachments: PNG File Screen Shot 2015-02-02 at 10.15.06.png    
Issue Links:
Relates
dependency
depends upon MGNLUI-3447 Update Magnolia UI to Vaadin 7.4 Closed
duplicate
duplicates MGNLUI-2247 When a user session timesout they rec... Closed
Template:
Acceptance criteria:
Empty
Task DoD:
[ ]* Doc/release notes changes? Comment present?
[ ]* Downstream builds green?
[ ]* Solution information and context easily available?
[ ]* Tests
[ ]* FixVersion filled and not yet released
[ ]  Architecture Decision Record (ADR)
Bug DoR:
[ ]* Steps to reproduce, expected, and actual results filled
[ ]* Affected version filled
Release notes required:
Yes
Date of First Response:

 Description   

We're seeing the red "Communication Problem" error message all the time when working on slow connections or some load on the server. This does not only happen on our solutions (i.e. where it could be our fault) but also on the Magnolia demo version. Is there a way to get Vaadin to relax a bit?



 Comments   
Comment by Daniel Lipp [ 08/Jun/15 ]

We see this also in the context of On Demand beta - with pretty fast servers and not-so-bad connections.

Comment by Philipp Bärfuss [ 19/Jun/15 ]

We are looking at it. It is pretty hard to pinpoint one specific root problem as this can be a symptom of many things:

  • slow connections
  • problems in the code (thread locks)
  • infrastructure setup (load balancing, proxy, ....)

It would help us if we can get some data.

apchelintcev: some ideas:

  • can we simulate a slow connection and see if there is a problem
  • can we hook in when the error happens to log some more data?
  • the main question is where the server is reached (and slow) or if the connectivity is broken
Comment by Will Scheidegger [ 19/Jun/15 ]

Not sure if this is a Magnolia or a general Vaadin problem. We are seeing the exact same error message on a Vaadin app we wrote for Magnolia 4.5 (AdminCentral extension). So it's definitely not a Magnolia 5 problem.

Comment by Aleksandr Pchelintcev [ 19/Jun/15 ]

Apparently this seems to be highly related to this one: https://dev.vaadin.com/ticket/15254.

The fix (precisely this: https://gist.github.com/anonymous/f91bf03c3adeb7169420) was introduced in version 7.3.5 and hence will be present in 5.4 (we're using Vaadin 7.4.7 now).

Comment by Aleksandr Pchelintcev [ 23/Jun/15 ]

Linked Vaadin version update issue should improve the situation with these unfortunate communication problems.

Comment by Daniel Lipp [ 23/Jun/15 ]

FYI: I just used a tool to artificially slow down the connection (chrome has something build in for it): got "Invalid status code 0" in the browser - server log (catalina.out) showed:

Jun 22, 2015 12:08:25 PM com.vaadin.server.communication.ServerRpcHandler parseInvocation
WARNING: RPC call to v.v received for connector 235 but no such connector could be found. Resynchronizing client.
Comment by Mikaël Geljić [ 02/Jul/15 ]

Indeed, as Sasha mentioned, this doesn't seem to affect 5.4, and there is no change as such.

So I adjusted fixVersion to 5.3.x to reflect that. Meanwhile, in case having this fixed *only* in 5.4 is acceptable, we'll close this one as "won't fix".
If not, we'll have to check whether we can a. pick the Vaadin patch somehow, or b. upgrade Vaadin on 5.3 branch as well.

Comment by Zdenek Skodik [ 03/Jul/15 ]

It'd be nice if we can find some way to have this fixed for 5.3 branch as well, but no headaches otherwise.

Comment by Jan Haderka [ 02/Aug/15 ]

This issue doesn't occur in Magnolia 5.4.

To work around the problem in Magnolia 5.3.x, those affected by the issue need to upgrade Vaadin from version 7.2 shipped with Magnolia 5.3.x to version 7.4 that contains fix for the issue.

To do so, it should be enough to add extra dependency in the webapp to override that coming from Magnolia directly. If you are not using maven to build your Magnolia instance, you need to replace Vaadin 7.2 and related libraries with Vaadin 7.4 in your WEB-INF/lib folder.

Since "fix" for this problem requires upgrade of major version of included library and might produce undesirable side effects under certain circumstances. Magnolia generally doesn't make upgrades of such libraries in maintenance releases, but only as part of major release, which in this case is already out and contains upgraded library and fix for the issue.

Thank you for your understanding.

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