diff options
| -rw-r--r-- | src/rabbit_queue_index.erl | 34 |
1 files changed, 17 insertions, 17 deletions
diff --git a/src/rabbit_queue_index.erl b/src/rabbit_queue_index.erl index 3158a1b3a7..34bb9920ec 100644 --- a/src/rabbit_queue_index.erl +++ b/src/rabbit_queue_index.erl @@ -43,27 +43,27 @@ %% %% Publishes and delivery notes are written directly to the segment %% files. The segment is found by dividing the sequence id by the the -%% max number of entries per segment. Only the relative sequeuence +%% max number of entries per segment. Only the relative sequence %% within the segment is recorded as the sequence id within a segment -%% file (i.e. sequeuence id modulo max number of entries per -%% segment). This is keeps entries as small as possible. Publishes and +%% file (i.e. sequence id modulo max number of entries per segment). +%% This is keeps entries as small as possible. Publishes and %% deliveries are only ever going to be received in contiguous -%% ascending order, with publishes following the tail of the queue and -%% deliveries following the head of the queue. +%% ascending order. %% %% Acks are written to a bounded journal and are also held in memory, -%% in a dict with the segment file as the key. When the journal gets -%% too big, or flush_journal is called, the journal is (possibly -%% incrementally) flushed out to the segment files. As acks can be -%% received from any delivered message in any order, this journal -%% reduces seeking, and batches writes to the segment files, keeping -%% performance high. The flush_journal/1 function returns a boolean -%% indicating whether there is more flushing work that can be -%% done. This means that the process can call this whenever it has an -%% empty mailbox, only a small amount of work is done, allowing the -%% process to respond quickly to new messages if they arrive, or to -%% call flush_journal/1 several times until the result indicates there -%% is no more flushing to be done. +%% in a dict with the segment file as the key. Again, the records are +%% fixed size: the entire sequence id is written and is limited to a +%% 64-bit unsigned integer. When the journal gets too big, or +%% flush_journal is called, the journal is (possibly incrementally) +%% flushed out to the segment files. As acks can be received from any +%% delivered message in any order, this journal reduces seeking, and +%% batches writes to the segment files, keeping performance high. The +%% flush_journal/1 function returns a boolean indicating whether there +%% is more flushing work that can be done. This means that the process +%% can call this whenever it has an empty mailbox, only a small amount +%% of work is done, allowing the process to respond quickly to new +%% messages if they arrive, or to call flush_journal/1 several times +%% until the result indicates there is no more flushing to be done. %% %% On startup, the ack journal is read along with all the segment %% files, and the ack journal is fully flushed out to the segment |