What benefits does java-monitor has over visualvm?

[Wirianto Djunaidi]

Hi Kees,

As the subject says, I'm wondering what other benefits java-monitor has over what visualvm?

One thing I can think of is online/web-based monitoring, while visualvm can do remote monitoring but not through web...but on the other hand, visualvm offers benefits like taking thread/heap dump and analysing them later.

Cheers,
Wirianto

[Kees Jan Koster]

Dear Wirianto,

You nailed it. Heap dumps are impractical because of their size and file format nastiness between JVM versions.

Java-monitor lets you look at what happened in a JVM while it is no longer running. You can restart a JVM that has died without worrying about destroying evidence that may lead to resolving the root cause of a crash.

So there is a tradeoff you can make. One has the benefit of being closer to the JVM, while the other has the benefit of being farther away. In fact, I use both tools. ;)

Kees Jan

[Wirianto Djunaidi]

Ah, how does java-monitor allow viewing dead JVM session? How far in the JVM history does it keep? I assume this is also limited to the amount of storage space to keep the stats.

I'm looking at the website, it seems to imply live session monitoring only.

[Ulf Dittmer]

The basic version charts data over 2 days. You can upgrade that to a week, a month or a year. Attached are examples of the 2-day and the 1-week chart.

Edit: Not sure why the graphs are part black here - there is a time line along the X axis. But you can see how the last part of the 1-week chart corresponds to the 2-day chart.

[Kees Jan Koster]

Thanks Ulf.

Wirianto: if you look at the top graph you can see that that JVM was restarted once or twice. You can see the data across restarts easily.

[Wirianto Djunaidi]

Thanks for the chart Ulf. My follow up question was how java-monitor allows viewing of not-running JVM session? Does java-monitor has list of previous JVM sessions to view? Because those chart can be just showing current live session which has been alive for past 2-days or 1-week.

-DJ

[Kees Jan Koster]

Dear Wirianto,

Ah, now I understand the question: Java-monitor does not make new 'sessions' for each restart. We just collect data over time and graph it. If you switch off a JVM for a few hours and then start it back up, that will show in the graphs as a section where no data is available.

Kees Jan

PS. And each Tuesday you get an email with the overview of the availability and number of restarts over the past week.

[Wirianto Djunaidi]

I'm sorry Kees from being slow. What should I look at to see JVM restart from that top-chart? Looking at sudden dip of Heap usage or dip in Max Heap?

-DJ

[Wirianto Djunaidi]

Ah, I see your response after I posted my follow up question. Thanks for the answer Kees.

-DJ

[Kees Jan Koster]

Dear Wirianto,

No problem.

Kees Jan