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Poco Forums • View topic - Another wild idea about cause of "lost messages"

Another wild idea about cause of "lost messages"

Help and advice on using PocoMail

Moderators: Eric, Tomas, robin

Postby Pete » Wed Aug 11, 2004 3:08 pm

I just did a quick test. I sent myself a message, downloaded it, then checked the mailbox files (.dat, .idx, and .mbx). I repeated this three times. Each time, PocoMail immediately added the message to the .idx and .mbx files. So according to this test, the problem either has been fixed or perhaps the problem never existed.

However, I tested this with a very small mailbox. I don't know the rules that PocoMail uses when it determines when to cache mailboxes and when to write the cached data to disk. I think that it would be a good idea if someone with a very large mailbox can test this (if you can figure out how to make a message that you send to yourself download directly into the very large mailbox). You might have to click on the mailbox in the GUI first to make sure that PocoMail loads it into memory before you run the test.
Pete
 

Postby tribble » Wed Aug 11, 2004 3:23 pm

1. I close all open apps FIRST, then shutdown/restart windows.
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Postby Sandy » Wed Aug 11, 2004 4:12 pm

I close all open apps FIRST, then shutdown/restart windows.


So do I. I can't imagine doing it any other way except by accident. It just seems prudent. OTOH, I rarely shut down windows at all. I leave XP running for weeks at a time without a re-boot. I run a business with this multi-system network and don't risk bells and whistles -- which in my experience evitably bring instablity. I stay well away from the bleeding edge.....and, knock on wood, I seem to suffer few problems.
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Postby Pete » Wed Aug 11, 2004 6:45 pm

Yah, I also close all of my apps first before I logout. However, (1) I have automation software on my PC that makes this easy for me but maybe this is too tedious for other people, especially if they always have many apps open including several that can only be closed by manually right-clicking on each corresponding icon in Windows' System Tray, and (2) I don't think that it's asking too much for PocoMail to listen for Windows logout/restart/shutdown events and close itself gracefully. I would guess that there are many Windows users who don't manually close all open apps before logging out of Windows either because they don't know better or because they expect that all Windows programs automatically handle these system events (I think that this is a fair and justified expectation).

Anyway, I personally think that either method is fine and that ideally it wouldn't matter how people do it because all Windows apps should gracefully handle all of these events. For right now, all that I care about is to find out if PocoMail safely handles the situation where someone does a logout/restart/shutdown without first closing PocoMail.

I think that I've found a reproducible example that shows that PocoMail does not always gracefully close. Note that I'm using Windows XP Home Edition sp1. Try this if you want:

  1. Delete all messages from the "In" and "Trash" mailboxes. I realize that some people keep messages in the "In" box instead of distributing them elsewhere. Maybe the test will still work without this step, but just so you know, when I ran the test, both of these mailboxes were initially empty.
  2. Compress the "In" and "Trash" mailboxes.
  3. If you don't always use the option, temporarily enable "Tools > General Options > Empty Trash On Exit"
  4. Go to a mailbox with messages in it, hold down the Ctrl key, drag a message to the "In" mailbox, and then release the Ctrl key.
  5. Click on the "In" mailbox and delete the message (I did this by clicking on the toolbar Delete button, but maybe this doesn't matter).
  6. "FIRST TIME": Use "File > Exit", then re-start PocoMail. Click on the In box and the message is gone. Click on the Trash box and the message is gone. This is the expected behavior. Now redo all of these steps from the beginning, but this time, do "second time" instead of "first time".
  7. "SECOND TIME": Logout of Windows, then login again and start PocoMail. Click on the In box and the message is still there! Click on the Trash box and the message is still there!

Assuming that other people will be able to reproduce my test results, I will try to summarize what I think is happening. I think that PocoMail is either completely ignoring certain Windows events or that PocoMail is handling the events but is not saving the information to disk that it has cached in memory. Possibly, this might include information such as the DBGood.ini and DBSpam.ini word lists, not just mailbox index (.idx) information.

I think that it's fair to ask that PocoMail flush its caches when it receives notification of Windows events such as logout/restart/shutdown and *perhaps* it should also do this for other events such as Standby and Hibernate. Of course, this would also apply to Barca and all of PSI's other products.
Pete
 

Postby robin » Wed Aug 11, 2004 7:24 pm

Pete wrote:Good point, Robin. I should have been more specific. I think that the issue is with the index files (.idx). If they are not updated before the logout/restart/shutdown, then that would be one cause of messages that do not appear in the GUI after re-starting PocoMail until after the mailbox is compressed.
I absolutely agree with that view, Pete.
robin
 

Postby robin » Wed Aug 11, 2004 7:28 pm

Pete wrote:However, I tested this with a very small mailbox. I don't know the rules that PocoMail uses when it determines when to cache mailboxes and when to write the cached data to disk. I think that it would be a good idea if someone with a very large mailbox can test this (if you can figure out how to make a message that you send to yourself download directly into the very large mailbox). You might have to click on the mailbox in the GUI first to make sure that PocoMail loads it into memory before you run the test.
Pete - the mailbox that I used for the tests that I did was 3Mb. Do you see this as big enough?
robin
 

Postby frazmi » Wed Aug 11, 2004 10:25 pm

And my test, which duplicated robin's results, was on an 11MB In mailbox.
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Postby frazmi » Wed Aug 11, 2004 10:46 pm

I ran through Pete's sequence of steps. I got exactly the same results as described.

Then, I turned off "Empty trash on exit" and reran the test. The results were the same. That is, after I deleted the message from the In box, it was present after restarting Windows. Thus, I conclude that the setting of "Empty trash on exit" is not critical.

I also got the same behavior (one time only) when shutting down Poco using the "X" button, rather than File-Exit. This was not reproducible, however.
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Postby frazmi » Wed Aug 11, 2004 11:58 pm

Here's another data point regarding the idx file.

Please refer to this thread for details. This is another repeatable example of a problem that might be linked to how Poco caches and writes the idx file to disk. Basically, it's a repeatable AV error scenario (on XP and Win2K systems) that involves the idx file.
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Postby hessi » Thu Aug 12, 2004 5:59 am

Hi fellow researchers :)

It's nice that somebody is looking into this - I think the request of a poll in the other (now locked) thread is a good idea I think. I think it's also a good idea to share system information of the affected users, additional software installed etc. to get some similarities.

What came into my mind - is it possible that a 'timing' problem is the cause of this, e.g. switching quickly from folder to folder so the index files couldn't be updated? I'm in no way a QA expert, so forgive me if this is completely nonsense ...
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Postby frazmi » Thu Aug 12, 2004 3:50 pm

hessi, I've also thought that a timing (or "race" condition) might be to blame, especially since some of these problems seem to occur more often when "moving fast" in Poco. For example, I have a 2-script pair that I run on some messages.

If I run them like this...
Script-1 "Mississippi-1 Mississippi-2 Mississippi-3" Script-2,
(that is, with a 3-second pause) they never fail.

If I run them like this:
Script-1 Script-2,
(that is, with no pause) then Script 2 often fails with an AV error.

Since Script 1 modifies the subject of the email, it's reasonable to wonder whether the AV error is related to how Poco handles the links between the idx and mbx files, and how Poco handles the in-memory cache of these files.
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Postby Raffael » Sun Aug 15, 2004 9:54 am

I am pleased to see that my now locked thread did move some things! You are all doing a very good job. Thanks! :)

I've also thought that a timing (or "race" condition) might be to blame, especially since some of these problems seem to occur more often when "moving fast" in Poco.


After having read every posts of this thread I have been trying hard to remember what steps exactly I did when about 30 messages suddenly were "gone" from my In mailbox. After the dl, all the messages were appearing normally in the In mailbox and many were normally distributed in other customised mailboxes and sub-mailboxes. I first read a couple of messages in the In mailbox and replied to some of them. Some minutes later I opened some of my yellow marked customised mailboxes and probably jumped quickly from one to another to have a overview of the new headers. Then I went back to the In mailbox and at that moment a part of the messages had disappeared. Interestingly some of the ones I had already read were still there and some others not.

I think that the timing factor can explain this strange behaviour, maybe linked with an NAV shield activity (but then not logged anywere) or maybe not, simply due to a caching timing problem of the idx file...
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Postby frazmi » Sun Aug 15, 2004 2:11 pm

If you can get to something even partially repeatable (like my 2 script scenario), and that can be posted (or at least sent to PSI for analysis) then it becomes much more useful in tracking down the actual problem -- wherever it lies.

I posted the scripts in the "old" forum, and a couple of people responded that "they looked good -- should not cause AV". One person, I forget who, did point out a minor flaw, but I fixed that and the scripts still fail in the same way.
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Postby Pete » Fri Aug 27, 2004 8:04 pm

Pete wrote:I think that it's fair to ask that PocoMail flush its caches when it receives notification of Windows events such as logout/restart/shutdown and *perhaps* it should also do this for other events such as Standby and Hibernate. Of course, this would also apply to Barca and all of PSI's other products.

Good news! The latest beta of PocoMail gracefully handles MS Windows' "Logout event". Although I didn't test it, I assume that it (and Barca) will also handle the Restart & Shutdown events. The enhancement should be available when v3.2 of PocoMail is officially released.

p.s. Thanks PSI!

p.p.s. I'm not saying that this will solve everyone's problems, but it should solve some problems, and in general, it will make PocoMail and Barca more robust.
Pete
 

Postby frazmi » Sat Aug 28, 2004 3:19 am

Yes, I agree that this is good news. And it shows that sometimes even partially-cooked ideas and half-baked problem statements can help PSI identify improvements in the program.
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