maria-developers team mailing list archive

[Kristian Nielsen <knielsen@xxxxxxxxxxxxxxx>]

Pavel Ivanov <pivanof@xxxxxxxxxx> writes:

> Sorry, I didn't quite understand.

Sorry for being unclear, let me elaborate:

> You didn't mention <log-bin>.state here. Is it intentional? Does it
> try to look into <log-bin>.state after rpl_slave_state and binlogs? Or
> e.g. in the situation when binlogs are not found?

There is just a single binlog state.

The binlog state consists of the last GTID logged into the binlog for every
(domain_id, server_id) pair. It also remembers the most recent GTID per
domain.

During normal server operation, the binlog state is kept only in-memory.

The binlog state can be recovered from the binlog simply by scanning and
recording every GTID encountered on the way. We do this after a crash.

However, as an optimisation, to avoid having to scan binlog files at normal
startup, we write out the binlog state to <log-bin>.state at server shutdown
and read it back in at server startup. This is the only use of the file
<log-bin>.state.

>> <log-bin>.state contains the current binlog state at the time of
>> shutdown. This is used to be able to output the correct Gtid_list event at the
>> start of the new binlog created at server startup, and also to initialise the
>> sequence number counter for new events.
>
> Again it "used to be" which means it's not used to do that anymore?

Just bad wording on my part, I meant "it is used", not that "it used to be".

So to clarify:

The server maintains an in-memory struct rpl_binlog_state with last GTIDs
binlogged per-domain and per-(domain_id,server_id).

At server shutdown, this in-memory state is saved to <log-bin>.state.

At server startup, if we detect that binlog was properly closed and we do not
need to do crash recovery, the in-memory struct rpl_binlog_state is
initialised from the file <log-bin>.state.

If we detect that we crashed prior and need to do crash recovery,
<log-bin>.state is not consulted. Instead the in-memory struct
rpl_binlog_state is initialised during the scan of the binlog, as part of
crash recovery.

I hope this makes things clear,

 - Kristian.