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authorMicael Karlberg <[email protected]>2012-01-09 17:50:47 +0100
committerMicael Karlberg <[email protected]>2012-01-12 12:13:11 +0100
commitdaf5b0eeb6f0d8c805f7a0e2fc117c8c788b855c (patch)
tree1a67da27edd104358aef66e269ba63a660804566 /lib/snmp/src/agent/snmpa_vacm.erl
parent021d5c2e49e623d4f43c0cc88a097bc99f3564e6 (diff)
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[snmp/agent] Creating a unique temporary file whe dumping vacm
Attempting to create a unique temporary file when dumping the vacm table to disk. OTP-9851
Diffstat (limited to 'lib/snmp/src/agent/snmpa_vacm.erl')
-rw-r--r--lib/snmp/src/agent/snmpa_vacm.erl43
1 files changed, 42 insertions, 1 deletions
diff --git a/lib/snmp/src/agent/snmpa_vacm.erl b/lib/snmp/src/agent/snmpa_vacm.erl
index 892dc265f1..c31b8e61a3 100644
--- a/lib/snmp/src/agent/snmpa_vacm.erl
+++ b/lib/snmp/src/agent/snmpa_vacm.erl
@@ -266,9 +266,24 @@ dump_table(true) ->
dump_table(_) ->
ok.
+
+%% We should really make an effort to serialize the dumping
+%% to ensure that several processes that dump at-the-same-time
+%% do not trash each others dumps.
+%% <SUGGESTION>
+%% Send the request to the master agent, which, if there is no
+%% dumper already running, spawns a (temporary) dumper process.
+%% If there is already a running dumper process, instead increment
+%% the dump_request counter.
+%% When the dumper process exits, the master agent checks the
+%% the dump_request counter, and if that is greated than zero,
+%% create another dumper process and resets the counter.
+%% In this way the dumping is serializede, but the master-agent
+%% process is not burdened by the dumping.
+%% </SUGGESTION>
dump_table() ->
[{_, FName}] = ets:lookup(snmp_agent_table, snmpa_vacm_file),
- TmpName = FName ++ ".tmp",
+ TmpName = unique(FName),
case ets:tab2file(snmpa_vacm, TmpName) of
ok ->
case file:rename(TmpName, FName) of
@@ -283,6 +298,32 @@ dump_table() ->
[FName, Reason])
end.
+%% This little thing is an attempt to create a "unique" filename
+%% in order to minimize the risk of two processes at the same
+%% time dumping the table.
+unique(Pre) ->
+ {A, B, C} = os:timestamp(),
+ {D, _} = erlang:statistics(reductions),
+ {E, _} = erlang:statistics(runtime),
+ {F, _} = erlang:statistics(wall_clock),
+ {G, H, _} = erlang:statistics(garbage_collection),
+ Data = [A, B, C, D, E, F, G, H],
+ unique(Pre, Data, 0).
+
+unique(Pre, [], Unique) ->
+ PidPart = unique_pid(),
+ lists:flatten(io_lib:format("~s.~s~w.tmp", [Pre, PidPart, Unique]));
+unique(Pre, [H|T], Unique) ->
+ unique(Pre, T, Unique bxor H).
+
+unique_pid() ->
+ case string:tokens(pid_to_list(self()), [$<,$.,$>]) of
+ [A, B, C] ->
+ A ++ B ++ C ++ ".";
+ _ ->
+ ""
+ end.
+
%%-----------------------------------------------------------------
%% Alg.