I would like to ask about Mnesia backup: 1. How to periodically create backup of Mnesia DB of a node? 2. How do to copy backup files to other machines and use them there?
Regards.
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On Sun, 30 Aug 2009, ngocdaothanh wrote: > Hi everyone,
> I would like to ask about Mnesia backup: > 1. How to periodically create backup of Mnesia DB of a node?
You can have a gen_server which uses timer:send_interval/2 combined with handle_info/2 to trigger the backups. You can back up everything with mnesia:backup/1. In case the backup takes a very long time you should twiddle something in the gen_server state to prevent starting a new backup while an old one is happening.
> 2. How do to copy backup files to other machines and use them there?
Is this about the actual file movement, or about whether a mnesia backup done on cluster A can be restored on cluster B?
On EC2, I store the backups on S3 via s3fs, then use mnesia:restore/2 when I want to restore the backup. I haven't tried to restore a backup on a cluster when all the node names have changed from when the backup was performed.
-- p
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> > I would like to ask about Mnesia backup: > > 1. How to periodically create backup of Mnesia DB of a node?
> You can have a gen_server which uses timer:send_interval/2 combined with > handle_info/2 to trigger the backups. You can back up everything with > mnesia:backup/1. In case the backup takes a very long time you should > twiddle something in the gen_server state to prevent starting a new backup > while an old one is happening.
No need for the timer though, just use the gen_server's own timeout return value. Combine this with calculating a timeout value using the until_next_time() function from crone and you can have nicely scheduled backups.
Minimal, untested and not even compiled example, started with something like mybackup:start_link("DB.BAK", {daily, {every, {1, hr}, {between, {12, 0, 0, am}, {11, 59, 59, pm}}}}) .
handle_info(timeout, {Backup_File, Backup_When} = State) -> mnesia:backup(Backup_File), % HACK: Just in case it took less than a second, make sure we don't do it again right away. timer:sleep(1000), {noreply, State, 1000*crone:until_next_time(Backup_When)}.
> Is this about the actual file movement, or about whether a mnesia backup done on cluster A can be restored on cluster B?
I mean for a same version of Erlang, is the default backup file cross- platform and can be restored anywhere just like a PostgreSQL backup file? How can I create backup file on a remote server running Ubuntu, then restore it to my local Snow Leopard laptop? I heard somewhere that once created a Mnesia DB will be fixed to a node name, simply copying it doesn't work.
> until_next_time() function from crone
crone is very interesting. Where can I find the latest version of it?
Regards.
On Sep 1, 2:34 am, Robert Raschke <rtrli...@googlemail.com> wrote:
> On Mon, Aug 31, 2009 at 5:43 PM, Paul Mineiro <paul-trape...@mineiro.com>wrote:
> > Inline.
> > -- p
> > On Sun, 30 Aug 2009, ngocdaothanh wrote:
> > > Hi everyone,
> > > I would like to ask about Mnesia backup: > > > 1. How to periodically create backup of Mnesia DB of a node?
> > You can have a gen_server which uses timer:send_interval/2 combined with > > handle_info/2 to trigger the backups. You can back up everything with > > mnesia:backup/1. In case the backup takes a very long time you should > > twiddle something in the gen_server state to prevent starting a new backup > > while an old one is happening.
> No need for the timer though, just use the gen_server's own timeout return > value. Combine this with calculating a timeout value using the > until_next_time() function from crone and you can have nicely scheduled > backups.
> Minimal, untested and not even compiled example, started with something like > mybackup:start_link("DB.BAK", {daily, {every, {1, hr}, {between, {12, 0, 0, > am}, {11, 59, 59, pm}}}}) .
> handle_info(timeout, {Backup_File, Backup_When} = State) -> > mnesia:backup(Backup_File), > % HACK: Just in case it took less than a second, make sure we don't do > it again right away. > timer:sleep(1000), > {noreply, State, 1000*crone:until_next_time(Backup_When)}.
> Robby
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> > Is this about the actual file movement, or about whether a mnesia backup > done on cluster A can be restored on cluster B?
> I mean for a same version of Erlang, is the default backup file cross- > platform and can be restored anywhere just like a PostgreSQL backup > file? How can I create backup file on a remote server running Ubuntu, > then restore it to my local Snow Leopard laptop? I heard somewhere > that once created a Mnesia DB will be fixed to a node name, simply > copying it doesn't work.
If you just want the contents of some/all tables restored, you can use the backup anywhere. If you want the entire database rebuilt from scratch using the backup, the node names have to match. There is a way to change node names in the backup file if you need the latter. Refer to the Mnesia user guide for details.
