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1 | package # hide from pause until we figure it all out |
2 | DBIx::Class::Storage::BlockRunner; |
3 | |
4 | use Sub::Quote 'quote_sub'; |
5 | use DBIx::Class::Exception; |
6 | use DBIx::Class::Carp; |
7 | use Context::Preserve 'preserve_context'; |
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8 | use DBIx::Class::_Util 'is_exception'; |
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9 | use Scalar::Util qw(weaken blessed reftype); |
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10 | use Try::Tiny; |
11 | use Moo; |
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12 | use warnings NONFATAL => 'all'; |
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13 | use namespace::clean; |
14 | |
15 | =head1 NAME |
16 | |
17 | DBIx::Class::Storage::BlockRunner - Try running a block of code until success with a configurable retry logic |
18 | |
19 | =head1 DESCRIPTION |
20 | |
21 | =head1 METHODS |
22 | |
23 | =cut |
24 | |
25 | has storage => ( |
26 | is => 'ro', |
27 | required => 1, |
28 | ); |
29 | |
30 | has wrap_txn => ( |
31 | is => 'ro', |
32 | required => 1, |
33 | ); |
34 | |
35 | # true - retry, false - rethrow, or you can throw your own (not catching) |
36 | has retry_handler => ( |
37 | is => 'ro', |
38 | required => 1, |
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39 | isa => quote_sub( q{ |
40 | (Scalar::Util::reftype($_[0])||'') eq 'CODE' |
9345b14c |
41 | or DBIx::Class::Exception->throw('retry_handler must be a CODE reference') |
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42 | }), |
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43 | ); |
44 | |
45 | has retry_debug => ( |
46 | is => 'rw', |
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47 | # use a sub - to be evaluated on the spot lazily |
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48 | default => quote_sub( '$ENV{DBIC_STORAGE_RETRY_DEBUG}' ), |
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49 | lazy => 1, |
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50 | ); |
51 | |
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52 | has max_attempts => ( |
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53 | is => 'ro', |
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54 | default => 20, |
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55 | ); |
56 | |
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57 | has failed_attempt_count => ( |
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58 | is => 'ro', |
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59 | init_arg => undef, # ensures one can't pass the value in |
60 | writer => '_set_failed_attempt_count', |
61 | default => 0, |
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62 | lazy => 1, |
63 | trigger => quote_sub(q{ |
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64 | $_[0]->throw_exception( sprintf ( |
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65 | 'Reached max_attempts amount of %d, latest exception: %s', |
66 | $_[0]->max_attempts, $_[0]->last_exception |
67 | )) if $_[0]->max_attempts <= ($_[1]||0); |
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68 | }), |
69 | ); |
70 | |
71 | has exception_stack => ( |
72 | is => 'ro', |
73 | init_arg => undef, |
74 | clearer => '_reset_exception_stack', |
75 | default => quote_sub(q{ [] }), |
76 | lazy => 1, |
77 | ); |
78 | |
79 | sub last_exception { shift->exception_stack->[-1] } |
80 | |
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81 | sub throw_exception { shift->storage->throw_exception (@_) } |
82 | |
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83 | sub run { |
84 | my $self = shift; |
85 | |
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86 | $self->_reset_exception_stack; |
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87 | $self->_set_failed_attempt_count(0); |
88 | |
89 | my $cref = shift; |
90 | |
91 | $self->throw_exception('run() requires a coderef to execute as its first argument') |
92 | if ( reftype($cref)||'' ) ne 'CODE'; |
93 | |
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94 | my $storage = $self->storage; |
95 | |
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96 | return $cref->( @_ ) if ( |
97 | $storage->{_in_do_block} |
98 | and |
99 | ! $self->wrap_txn |
100 | ); |
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101 | |
102 | local $storage->{_in_do_block} = 1 unless $storage->{_in_do_block}; |
103 | |
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104 | return $self->_run($cref, @_); |
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105 | } |
106 | |
107 | # this is the actual recursing worker |
108 | sub _run { |
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109 | # internal method - we know that both refs are strong-held by the |
110 | # calling scope of run(), hence safe to weaken everything |
111 | weaken( my $self = shift ); |
112 | weaken( my $cref = shift ); |
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113 | |
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114 | my $args = @_ ? \@_ : []; |
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115 | |
116 | # from this point on (defined $txn_init_depth) is an indicator for wrap_txn |
117 | # save a bit on method calls |
118 | my $txn_init_depth = $self->wrap_txn ? $self->storage->transaction_depth : undef; |
119 | my $txn_begin_ok; |
120 | |
121 | my $run_err = ''; |
122 | |
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123 | return preserve_context { |
124 | try { |
125 | if (defined $txn_init_depth) { |
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126 | $self->storage->txn_begin; |
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127 | $txn_begin_ok = 1; |
128 | } |
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129 | $cref->( @$args ); |
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130 | } catch { |
131 | $run_err = $_; |
132 | (); # important, affects @_ below |
133 | }; |
134 | } replace => sub { |
135 | my @res = @_; |
136 | |
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137 | my $storage = $self->storage; |
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138 | my $cur_depth = $storage->transaction_depth; |
139 | |
140 | if (defined $txn_init_depth and $run_err eq '') { |
141 | my $delta_txn = (1 + $txn_init_depth) - $cur_depth; |
142 | |
143 | if ($delta_txn) { |
144 | # a rollback in a top-level txn_do is valid-ish (seen in the wild and our own tests) |
145 | carp (sprintf |
146 | 'Unexpected reduction of transaction depth by %d after execution of ' |
147 | . '%s, skipping txn_commit()', |
148 | $delta_txn, |
7d534e68 |
149 | $cref, |
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150 | ) unless $delta_txn == 1 and $cur_depth == 0; |
151 | } |
152 | else { |
153 | $run_err = eval { $storage->txn_commit; 1 } ? '' : $@; |
154 | } |
155 | } |
156 | |
157 | # something above threw an error (could be the begin, the code or the commit) |
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158 | if ( is_exception $run_err ) { |
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159 | |
160 | # attempt a rollback if we did begin in the first place |
161 | if ($txn_begin_ok) { |
162 | # some DBDs go crazy if there is nothing to roll back on, perform a soft-check |
163 | my $rollback_exception = $storage->_seems_connected |
164 | ? (! eval { $storage->txn_rollback; 1 }) ? $@ : '' |
165 | : 'lost connection to storage' |
166 | ; |
167 | |
168 | if ( $rollback_exception and ( |
169 | ! defined blessed $rollback_exception |
170 | or |
171 | ! $rollback_exception->isa('DBIx::Class::Storage::NESTED_ROLLBACK_EXCEPTION') |
172 | ) ) { |
173 | $run_err = "Transaction aborted: $run_err. Rollback failed: $rollback_exception"; |
174 | } |
175 | } |
176 | |
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177 | push @{ $self->exception_stack }, $run_err; |
178 | |
179 | # this will throw if max_attempts is reached |
180 | $self->_set_failed_attempt_count($self->failed_attempt_count + 1); |
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181 | |
182 | # init depth of > 0 ( > 1 with AC) implies nesting - no retry attempt queries |
183 | $storage->throw_exception($run_err) if ( |
184 | ( |
185 | defined $txn_init_depth |
186 | and |
187 | # FIXME - we assume that $storage->{_dbh_autocommit} is there if |
188 | # txn_init_depth is there, but this is a DBI-ism |
189 | $txn_init_depth > ( $storage->{_dbh_autocommit} ? 0 : 1 ) |
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190 | ) or ! $self->retry_handler->($self) |
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191 | ); |
192 | |
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193 | # we got that far - let's retry |
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194 | carp( sprintf 'Retrying %s (attempt %d) after caught exception: %s', |
195 | $cref, |
196 | $self->failed_attempt_count + 1, |
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197 | $run_err, |
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198 | ) if $self->retry_debug; |
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199 | |
200 | $storage->ensure_connected; |
201 | # if txn_depth is > 1 this means something was done to the |
4a0eed52 |
202 | # original $dbh, otherwise we would not get past the preceding if() |
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203 | $storage->throw_exception(sprintf |
204 | 'Unexpected transaction depth of %d on freshly connected handle', |
205 | $storage->transaction_depth, |
206 | ) if (defined $txn_init_depth and $storage->transaction_depth); |
207 | |
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208 | return $self->_run($cref, @$args); |
9345b14c |
209 | } |
210 | |
211 | return wantarray ? @res : $res[0]; |
212 | }; |
213 | } |
214 | |
0c11ad0e |
215 | =head1 AUTHOR AND CONTRIBUTORS |
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216 | |
0c11ad0e |
217 | See L<AUTHOR|DBIx::Class/AUTHOR> and L<CONTRIBUTORS|DBIx::Class/CONTRIBUTORS> in DBIx::Class |
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218 | |
219 | =head1 LICENSE |
220 | |
221 | You may distribute this code under the same terms as Perl itself. |
222 | |
223 | =cut |
224 | |
225 | 1; |