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# Setup $rpl_sync_chain, which is used by rpl_sync.inc. You normally
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# don't need to source this file, it should only be sourced by
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# $rpl_sync_chain is set to a string that specifies in what order
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# servers should be synchronized in include/rpl_sync.inc. This has the
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# form of a sequence of "chains" (with no separator between two
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# chains). Each chain begins with $rpl_server_count_length space
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# characters, followed by a sequence of numbers, each number
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# whitespace-padded to $rpl_server_count_length characters. Each
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# number in the sequence denotes a server, and the N'th server is a
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# master of the (N+1)'th server. For example, if $rpl_topology is
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# '1->2,2->3,3->1,2->4,5->6', then $rpl_sync_chain is ' 56 123124'.
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# [--let $rpl_debug= 1]
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# --source include/rpl_generate_sync_chain.inc
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# See include/rpl_init.inc
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--let $include_filename= rpl_generate_sync_chain.inc
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--source include/begin_include_file.inc
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# 0. Mark all servers as unseen and unsynced.
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# 1. Let S be a server that is marked unseen.
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# 2. Append S to the list of seen servers.
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# 3. Check how S is marked:
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# 3.1. If S has no master: append the list of seen servers (in
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# order from grand-master to grand-slave) to the end of
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# $rpl_sync_chain. Go to 3.
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# 3.2. Elseif S is marked as synced: append the list of seen
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# servers (in order from grand-master to grand-slave) to the
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# end of $rpl_sync_chain. Go to 3.
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# 3.3. Elseif S is marked as unsynced but seen: This means that the
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# graph of visited servers has a "6-shape": it is a loop with
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# a tail, such as 1->2->3->1->4->5. We should first sync the
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# loop, and then the tail. To ensure all servers in the loop
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# are synced, we must sync the loop two turns minus two
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# servers. For example, the loop 1->2->3->4->5->1 is fully
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# synced by this sequence of 1-step synchronizations:
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# 1->2->3->4->5->1->2->3->4. Hence we do this: in the list of
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# traversed servers (in order from grand-master to
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# grand-slave), find the first occurrence of S. Take the
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# sub-list starting at the 3rd server and ending at the first
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# occurrence of S. Append this sub-list it to the end of
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# $rpl_sync_chain. Then append the entire list of traversed
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# servers (in order from grand-master to grand-slave) to
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# $rpl_sync_chain. Go to 3.
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# 3.4. Else (i.e., S has a master and is not marked as seen or
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# synced): Mark S as seen. Set S=master(S) and go back to 2.
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# 4. For each server that is marked as seen, mark it as synced.
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# 5. If there are unseen servers, go back to 1.
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# $_rpl_server_marks holds the marks of all servers. The i'th character
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# corresponds to the mark of server i:
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# '0' = unseen & unmarked, '1' = seen & unsynced, '2' = seen & synced.
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--let $_rpl_server_marks= `SELECT REPEAT('0', $rpl_server_count)`
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--let $_rpl_start_server= $rpl_server_count
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--let $rpl_sync_chain=
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while ($_rpl_start_server)
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--let $_rpl_server= `SELECT RPAD('$_rpl_start_server', $rpl_server_count_length, ' ')`
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--let $_rpl_seen_list=
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--let $_rpl_continue_loop= 1
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while ($_rpl_continue_loop)
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--let $_rpl_master= `SELECT SUBSTRING('$rpl_master_list', 1 + ($_rpl_server - 1) * $rpl_server_count_length, $rpl_server_count_length)`
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# We need to delimit elements of $_rpl_seen_list with commas, so
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# that LOCATE() below will not find spurious matches that begin in
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# the middle of one element and end in the middle of next element.
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--let $_rpl_seen_list= $_rpl_server,$_rpl_seen_list
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# If server is marked seen or synced, or has no master
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if (`SELECT SUBSTRING('$_rpl_server_marks', $_rpl_server, 1) != 0 OR '$_rpl_master' = ''`)
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# If server is marked seen but not synced.
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if (`SELECT SUBSTRING('$_rpl_server_marks', $_rpl_server, 1) = 1`)
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# Get sub-list of servers to prepend to server list.
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# E.g., if topology is 1->2->3->4->1->5, then at this point
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# $_rpl_seen_list='1,2,3,4,1,5,' and we have to prepend '4,3,'
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# to it. Hence, the sub-list starts at position
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# 1+2*($rpl_server_count_length+1) and ends at the first
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# occurrence of ',1,' in the list.
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--let $_rpl_extra_list= `SELECT SUBSTRING('$_rpl_seen_list', 1 + 2 * ($rpl_server_count_length + 1), LOCATE(',$_rpl_server,', '$_rpl_seen_list') - 2 * ($rpl_server_count_length + 1))`
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--let $_rpl_seen_list= $_rpl_extra_list$_rpl_seen_list
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# Append the seen servers. Only need to append if the list
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# contains at least two elements.
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if (`SELECT LENGTH('$_rpl_seen_list') > $rpl_server_count_length + 1`)
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--let $rpl_sync_chain= $rpl_sync_chain$_rpl_no_server$_rpl_seen_list
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--let $_rpl_continue_loop= 0
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--let $_rpl_server_marks= `SELECT INSERT('$_rpl_server_marks', $_rpl_server, 1, '1')`
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--let $_rpl_server= $_rpl_master
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# Mark seen servers as synced
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--let $_rpl_server_marks= `SELECT REPLACE('$_rpl_server_marks', '1', '2')`
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# Get highest-numbered unmarked server.
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--let $_rpl_start_server= `SELECT IFNULL(NULLIF($rpl_server_count + 1 - LOCATE('0', REVERSE('$_rpl_server_marks')), $rpl_server_count + 1), 0)`
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# Strip commas: they were only needed temporarily.
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--let $rpl_sync_chain= `SELECT REPLACE('$rpl_sync_chain', ',', '')`
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--echo Generated \$rpl_sync_chain = '$rpl_sync_chain'
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--let $include_filename= rpl_generate_sync_chain.inc
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--source include/end_include_file.inc