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| -rw-r--r-- | src/rabbit_disk_queue.erl | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/src/rabbit_disk_queue.erl b/src/rabbit_disk_queue.erl index 63df5cc5d1..3914e93365 100644 --- a/src/rabbit_disk_queue.erl +++ b/src/rabbit_disk_queue.erl @@ -705,6 +705,17 @@ to_ram_disk_mode(State = #dqstate { operation_mode = disk_only, %% message cache helper functions %%---------------------------------------------------------------------------- +%% The purpose of the cache is not especially performance, though it +%% can help there too. The main purpose is to ensure that individual +%% messages that are sent to multiple queues, and then to disk, are +%% read back as the same binary object rather than multiples of +%% identical binary objects. This prevents memory explosion. +%% +%% We limit the cache in size. If we didn't, then we could have two +%% queues coming off the same exchange, receiving the same millions of +%% messages, then one queue gets drained, which would pull the entire +%% queue into the cache, which would potentially explode memory. + remove_cache_entry(MsgId, #dqstate { message_cache = Cache }) -> true = ets:delete(Cache, MsgId), ok. |