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