Yesterday I wrote about Java Mission Control, the current Java Monitoring Client distributed with Java 8 JDKs, on Twitter:
Java Mission Control could be an outstanding monitoring tool if it weren't buggy as hell.
This was the conclusion to a half-day monitoring session for a remote system that repeatedly went nuts the last weeks on special occasions. Yesterday was the first occasion where I could actually monitor the problems live but everything went wrong doing so and some problems with the MC tool actually made it worse.
This tweet was anwered by @klaraward, apparently the developer of Java Mission Control:
Can you be more specific about the bugs?
I really want to give constructive feedback. I'm a software product developer myself and sometimes have to cope with harsh comments about my creations, I know how this feels. I also know that there are certain situations where criticism naturally becomes harder than is really fair, and monitoring a system "in flagranti" on an occasion you waited days for but ultimately cannot do is such a situation.
So without further ado, and as I do not want to cram my feedback into 140 chars:
Hi Klara! Sorry for being rough. I really appreciate the tool and would love to have it work for me smoothly on coming occasions. Here are the problems that occured:
Resource Exhaustion/Performance degradation
There are situations where performance gets very slow, which I could not really nail down yet. Sometimes it seems that just running the client for longer times (that is: days) makes it very very slow with single clicks on any controls taking multiple seconds to show a reaction and the charts being updated only every 10 seconds. Then I need to restart the tool to get it responsive again. Note: I'm having "Historical Data Persistence" active all the time.
Another occasion where I see instant performance degradation is fiddling around with triggers, for example adding a custom trigger for a custom JMX metric, activating it and choosing the trigger action. After that I sometimes have the same very slow system as described above.
The alert dialog appearing without alerts
This happened to me after I unchecked the checkbox "Show dialog on alerts" on that very dialog. After that the dialog would reappear in random situations, sometimes every 5 seconds, without any alert in the list.
(I could do a cheap joke on this that I misinterpreted the meaning of the checkbox, with it being off actually meaning that the dialog would also show without alerts....but no I really want to be constructive here ;-)
JMX consoles not opening
On one JMC installation I'm having four different systems registered with their JMX connections. Sometimes, if I already have opened two of them JMX refuses to open any more. Instead if I double-click on the "MBean Server" (or right click choosing "Open JMX console") on a yet unopened system it selects one of the already open JMX console tabs.
I use Java Mission Control 5.5, the version coming with the latest Java 8 release, on two platforms: One being a Windows 7 64-Bit system, the other an Ubuntu 12.04 amd64. Both are not quite contemporary but run other Eclipse-based applications without problems. The effects occured on both, so I'm relatively sure that it is no platform specific thing.
However, some problems not mentioned above are Linux only, like parts of the windows flickering with the updating of the charts, or any operation on the trigger tab always taking very long. But this may be specific to my system.
So thanks Klara for accepting my feedback. If there is anything more I can do to help you analyzing these problems just contact me on twitter or here.