Offline snapshots

[HP]

Hi guys, do we have a way of creating offline snapshots safely while there is an active application which continues to log new events?

I thought of just instantiating a new instance of the application and pointing it to the same journal but then I wasn't sure how "safe" it would be and if there was a chance of corrupting the sequence number value by doing this.

It would be awesome if I could have a "read-only" replay of events onto my event sourced actor and then have it take a snapshot which I can use later for recovery or as a method of rebuilding internal state after a code change affected the structure of internal actor state for faster recovery on deployment of this change.

e.g.

Version 1 of Eventsourced Actor A is in production.

Version 2 of Eventsourced Actor A is in test/staging

I create an offline snapshot using Version 2 upto sequence number M

I deploy Version 2 to production, it picks up the snapshot with last command with sequence number M and continues to recover by replaying all events after M

Thanks,

Hiral

[Martin Krasser]

Hi Hiral,

as long as the new application is only recovering without writing new
Messages you should be fine. You just need to make sure that the new
application writes the snapshots to a different location, unless the
structure of the state covered by the snapshots didn't change.

Cheers,
Martin

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[HP]

Hi Martin, thanks, I figured that but I was hoping there would be some way to put the journal in "read-only" mode so that I don't accidentally write to it.  Not something I want to risk in prod.

If not, maybe we could add it to the wish list.

Thanks,

Hiral

[Martin Krasser]

On 11.11.13 08:08, HP wrote:

Hi Martin, thanks, I figured that but I was hoping there would be some way to put the journal in "read-only" mode so that I don't accidentally write to it.  Not something I want to risk in prod.

If not, maybe we could add it to the wish list.

This will be for sure supported by akka-persistence. Interested in opening a pull request for eventsourced (e.g. separating reads from writes in journals so that read-only journal can be created)?

[HP]

Created a PR for read only mode for journals.  https://github.com/eligosource/eventsourced/pull/137

Let me know what you think.

Thanks,

Hiral