Files
hydra/src/script/hydra-notify
Nikola Knezevic f79810bac1 Improve handling of Perl's block eval errors
Taken from `Perl::Critic`:

A common idiom in perl for dealing with possible errors is to use `eval`
followed by a check of `$@`/`$EVAL_ERROR`:

    eval {
        ...
    };
    if ($EVAL_ERROR) {
        ...
    }

There's a problem with this: the value of `$EVAL_ERROR` (`$@`) can change
between the end of the `eval` and the `if` statement. The issue are object
destructors:

    package Foo;

    ...

    sub DESTROY {
        ...
        eval { ... };
        ...
    }

    package main;

    eval {
        my $foo = Foo->new();
        ...
    };
    if ($EVAL_ERROR) {
        ...
    }

Assuming there are no other references to `$foo` created, when the
`eval` block in `main` is exited, `Foo::DESTROY()` will be invoked,
regardless of whether the `eval` finished normally or not. If the `eval`
in `main` fails, but the `eval` in `Foo::DESTROY()` succeeds, then
`$EVAL_ERROR` will be empty by the time that the `if` is executed.
Additional issues arise if you depend upon the exact contents of
`$EVAL_ERROR` and both `eval`s fail, because the messages from both will
be concatenated.

Even if there isn't an `eval` directly in the `DESTROY()` method code,
it may invoke code that does use `eval` or otherwise affects
`$EVAL_ERROR`.

The solution is to ensure that, upon normal exit, an `eval` returns a
true value and to test that value:

    # Constructors are no problem.
    my $object = eval { Class->new() };

    # To cover the possiblity that an operation may correctly return a
    # false value, end the block with "1":
    if ( eval { something(); 1 } ) {
        ...
    }

    eval {
        ...
        1;
    }
        or do {
            # Error handling here
        };

Unfortunately, you can't use the `defined` function to test the result;
`eval` returns an empty string on failure.

Various modules have been written to take some of the pain out of
properly localizing and checking `$@`/`$EVAL_ERROR`. For example:

    use Try::Tiny;
    try {
        ...
    } catch {
        # Error handling here;
        # The exception is in $_/$ARG, not $@/$EVAL_ERROR.
    };  # Note semicolon.

"But we don't use DESTROY() anywhere in our code!" you say. That may be
the case, but do any of the third-party modules you use have them? What
about any you may use in the future or updated versions of the ones you
already use?
2020-05-26 11:19:43 +02:00

130 lines
3.4 KiB
Perl
Executable File

#! /usr/bin/env perl
use strict;
use utf8;
use Hydra::Plugin;
use Hydra::Helper::Nix;
use Hydra::Helper::AddBuilds;
use IO::Select;
STDERR->autoflush(1);
binmode STDERR, ":encoding(utf8)";
my $config = getHydraConfig();
my $db = Hydra::Model::DB->new();
my @plugins = Hydra::Plugin->instantiate(db => $db, config => $config);
my $dbh = $db->storage->dbh;
$dbh->do("listen build_started");
$dbh->do("listen build_finished");
$dbh->do("listen step_finished");
sub buildStarted {
my ($buildId) = @_;
my $build = $db->resultset('Builds')->find($buildId)
or die "build $buildId does not exist\n";
foreach my $plugin (@plugins) {
eval {
$plugin->buildStarted($build);
1;
} or do {
print STDERR "error with $plugin->buildStarted: $@\n";
}
}
}
sub buildFinished {
my ($build, @deps) = @_;
my $project = $build->project;
my $jobsetName = $build->get_column('jobset');
if (length($project->declfile) && $jobsetName eq ".jobsets" && $build->iscurrent) {
handleDeclarativeJobsetBuild($db, $project, $build);
}
my @dependents;
foreach my $id (@deps) {
my $dep = $db->resultset('Builds')->find($id)
or die "build $id does not exist\n";
push @dependents, $dep;
}
foreach my $plugin (@plugins) {
eval {
$plugin->buildFinished($build, [@dependents]);
1;
} or do {
print STDERR "error with $plugin->buildFinished: $@\n";
}
}
$build->update({ notificationpendingsince => undef });
}
sub stepFinished {
my ($buildId, $stepNr, $logPath) = @_;
my $build = $db->resultset('Builds')->find($buildId)
or die "build $buildId does not exist\n";
my $step = $build->buildsteps->find({stepnr => $stepNr})
or die "step $stepNr does not exist\n";
$logPath = undef if $logPath eq "-";
foreach my $plugin (@plugins) {
eval {
$plugin->stepFinished($step, $logPath);
1;
} or do {
print STDERR "error with $plugin->stepFinished: $@\n";
}
}
}
# Process builds that finished while hydra-notify wasn't running.
for my $build ($db->resultset('Builds')->search(
{ notificationpendingsince => { '!=', undef } }))
{
my $buildId = $build->id;
print STDERR "sending notifications for build ${\$buildId}...\n";
buildFinished($build);
}
# Process incoming notifications.
my $fd = $dbh->func("getfd");
my $sel = IO::Select->new($fd);
while (1) {
$sel->can_read;
while (my $notify = $dbh->func("pg_notifies")) {
my ($channelName, $pid, $payload) = @$notify;
#print STDERR "got '$channelName' from $pid: $payload\n";
my @payload = split /\t/, $payload;
eval {
if ($channelName eq "build_started") {
buildStarted(int($payload[0]));
} elsif ($channelName eq "build_finished") {
my $buildId = int($payload[0]);
my $build = $db->resultset('Builds')->find($buildId)
or die "build $buildId does not exist\n";
buildFinished($build, @payload[1..$#payload]);
} elsif ($channelName eq "step_finished") {
stepFinished(int($payload[0]), int($payload[1]));
}
1;
} or do {
print STDERR "error processing message '$payload' on channel '$channelName': $@\n";
}
}
}