I've written a Parallel::ForkManager reproduction script in hopes others can review/test and provide feedback. It doesn't involve any convoluted event code.

I created a simple database by running sqlite3 test.db < test.sql where test.sql consists of:

DROP TABLE IF EXISTS test;

CREATE TABLE test (
    id VARCHAR(50),
    value VARCHAR(20)
);

INSERT INTO test VALUES ('test', 0);

[download]

Here is the code. Note that lowering the num of forks, and/or tweaking with sleeping will evade the issue... for a period only. It eventually creeps back in. The code below breaks nearly immediately (on my Raspberry Pi 3):

use warnings;
use strict;

use DBI;
use Parallel::ForkManager;

my $dbh = DBI->connect(
    "dbi:SQLite:dbname=test.db",
    "",
    "",
    {RaiseError => 1}
) or die $DBI::errstr;

my $pm = Parallel::ForkManager->new(20);

for (1..20){
    $pm->start and next;
    my $interval = $_ / 10;
    while (1){
        dbwrite($dbh, $interval);
        #print "$interval\n";
    }
}

while(1){
    my $sth = $dbh->prepare(
        "SELECT * FROM test WHERE id=?;"
    );
    $sth->execute('test');
    my $val = $sth->fetchrow_hashref()->{value};

    #sleep 1;
}

sub dbwrite {
    my ($dbh, $interval) = @_;
    my $sth = $dbh->prepare(
        'UPDATE test SET value=? WHERE id="test;"'
    );
    $sth->execute($interval);
};

[download]

On my more powerful laptop with an SSD disk, it takes ~10 seconds to break. Now, my application doesn't process nearly as fast as this script does. That said, it still isn't good, and I need to find a reliable solution.

Are there any reasonable fixes for this, or should I instead be looking at using a MySQL database on a remote server? DB read/writes in the real app I'm writing happen at most, every second, give or take.

I'd really, really like to avoid using an external DB if possible; I want this app to be self-contained. I can't use a memory db (ie. I don't know HOW to share a memory db between different processes, so any pointers here that I can test will be quite welcome as well).

Thanks for all the feedback Monks.

-stevieb

In reply to Re: DBD::SQLite "file is encrypted or is not a database" in running application (repro code) by stevieb
in thread [SOLVED]: DBD::SQLite "file is encrypted or is not a database" in running application by stevieb

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