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authorJay Nelson <[email protected]>2010-01-25 11:01:32 -0800
committerBjörn Gustavsson <[email protected]>2010-02-10 17:14:28 +0100
commit1686757b304b66050f54db8e0ce5ab758bde96af (patch)
tree4b23dd691ff970e43bc5bfb6dc87941facee621c /otp_build
parentada6afd00530d6569c41741cfd9d63311ff60f25 (diff)
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Add count_children/1 to supervisor.erl to determine the number of
children being managed without the memory impact of which_children/1 The function which_children/1 returns a list of the child processes currently being supervised, but it has the penalty of creating a new list thereby consuming more memory. In low memory situations it is often desirable to know which supervisor may have generated many processes, but the act of discovering the culprit should not cause the node to crash (or worse a different node if the kernel kills one randomly). The new function count_children/1 can give an indication of which supervisor is taxing resources the most without adding to the burden. Rather than creating a new list, it walks the supervisor's internal children structure using an accumulator function so that any used memory can be incrementally collected yet the resulting count can still be obtained. The return result of count_children/1 is a property list of counts containing: - {specs, Total_Num_Child_Specs} - {active, Num_Active_Child_Processes_Of_Supervisor_Or_Worker_Type} - {supervisors, Num_Supervisor_Type_Children_Including_Dead_Processes} - {workers, Num_Worker_Type_Children_Including_Dead_Processes} This patch was made in response to mailing list discussions of the problem diagnosing heavily taxed production systems. I cannot find the original request, but http://www.erlang.org/cgi-bin/ezmlm-cgi/4/35060 is my original post of the patch.
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