Tue Feb 28 13:38:31 PST 2006
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I have a "followup question" concerning #1485... When you ran into problems with your five node example shaped like... 1 --> 10 --> 11 --> 20 --> 21 (e.g. - 1 feeds 10 and 20, then 10 feeds 11, 20 feeds 21, and we have paths exactly corresponding to 2-way communications there...) It's not entirely clear what your path/listener configuration looked like. >From what I can see, it should look like the following: /* cbbrowne@[local]/dba2 slonyregress1=*/ select * from _slony_regress1.sl_path order by pa_server, pa_client; pa_server | pa_client | pa_conninfo | pa_connretry -----------+-----------+-------------+-------------- 1 | 10 | | 1 | 20 | | 10 | 1 | | 10 | 11 | | 11 | 10 | | 20 | 1 | | 20 | 21 | | 21 | 20 | | (8 rows) (Obviously, there would be more useful DSN values in a real system ;-).) Based on the above, and no subscription information, the current, production listen path builder builds the following: /* cbbrowne@[local]/dba2 slonyregress1=*/ select li_origin, li_receiver, li_provider from _slony_regress1.sl_listen order by li_origin, li_receiver, li_provider; li_origin | li_receiver | li_provider -----------+-------------+------------- 1 | 10 | 1 1 | 11 | 10 1 | 20 | 1 1 | 21 | 20 10 | 1 | 10 10 | 11 | 10 10 | 20 | 1 10 | 20 | 21 10 | 21 | 20 11 | 1 | 10 11 | 1 | 20 11 | 10 | 11 11 | 20 | 1 11 | 20 | 21 11 | 21 | 20 20 | 1 | 20 20 | 10 | 1 20 | 10 | 11 20 | 11 | 10 20 | 21 | 20 21 | 1 | 10 21 | 1 | 20 21 | 10 | 1 21 | 10 | 11 21 | 11 | 10 21 | 20 | 21 (26 rows) If I define the set and subscriptions as described: /* cbbrowne@[local]/dba2 slonyregress1=*/ select * from _slony_regress1.sl_set; set_id | set_origin | set_locked | set_comment --------+------------+------------+------------- 1 | 1 | | (1 row) /* cbbrowne@[local]/dba2 slonyregress1=*/ select * from _slony_regress1.sl_subscribe ; sub_set | sub_provider | sub_receiver | sub_forward | sub_active ---------+--------------+--------------+-------------+------------ 1 | 1 | 10 | | 1 | 1 | 20 | | 1 | 10 | 11 | | (3 rows) li_origin | li_receiver | li_provider -----------+-------------+------------- 1 | 10 | 1 1 | 11 | 10 1 | 20 | 1 1 | 21 | 20 10 | 1 | 10 10 | 11 | 10 10 | 20 | 1 10 | 21 | 20 11 | 1 | 10 11 | 1 | 20 11 | 10 | 11 11 | 20 | 1 11 | 21 | 20 20 | 1 | 20 20 | 10 | 1 20 | 10 | 11 20 | 11 | 10 20 | 21 | 20 21 | 1 | 10 21 | 1 | 20 21 | 10 | 1 21 The difference is these two listener entries, which, analytically, it makes sense can be dropped without adversely affecting the cluster. (If you think about it, node 21 is a *crummy* node for node 20 to use as a provider for events from node 10, and ditto for 21 as a provider to 20 for events from node 11.) li_origin | li_provider | li_receiver -----------+-------------+------------- 10 | 21 | 20 11 | 21 | 20 (2 rows) Would it be possible for you to provide a more exact list of what the (apparently wrong) listen network looked like? I don't see the existing calculation breaking down, in this case. Attached is a gzipped listing of my results so far; I took the material in bug #1485 and rewrote the examples to look as they should in the actual Slony-I schema. By the way, the algorithm that you propose seems only to differ in one material way from the existing one: The existing one will prefer more direct listen paths based on sl_subscribe to those of "lesser" status. That is what led to the 2 row difference above. That difference shouldn't cause the problem you observed, in that all it does is to eliminate some paths that wouldn't have been useful anyways. -------------- next part -------------- A non-text attachment was scrubbed... Name: testlisten.txt.gz Type: application/gzip Size: 925 bytes Desc: not available Url : http://gborg.postgresql.org/pipermail/slony1-general/attachments/20060228/8696ffd2/testlisten.txt.bin
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