Question about multi-master configuration.

[SeongUk Baek]

I'm testing multi-master configuration.

Gerrit : 2.11.x
Storage : NAS
Load balancer : HAProxy

Install the gerrit on differents servers

Sync is no problem.
load balancing and fail over is good.

The problem is web-session.
When I upload some changes and I connect by web, there occurs error like below.
=> The page you requested was not found, or you do not have permission to view this page.

And I loggin session is very strange.
Suddenly log out.

Could you please help how to configure web-session on multi-master.

Thanks a lot in advance

[lucamilanesio]

Multi-master isn't support AFAIK.

You will have lots of problems including:

1) Cache consistency

2) Index misalignment

3) Session management

4) Stream events

5) Transaction coordination

... is the list long enough? :-)

Some of them can be work rounded:

1) Set no-cache (but performance will suffer)

2) There is a plugin for index events distribution to other nodes

3) There is a plugin for storing the session on external flat-file

4) Use Kafka or RabbitMQ events bus

5) No solution (yet)

[SeongUk Baek]

Thanks for reply.

Is there any other way for a fail-over?

[Luca Milanesio]

See Ericsson's presentation at the Gerrit User Summit:

https://storage.googleapis.com/gerrit-talks/summit/2015/Scaling-Gerrit-Ericsson.pdf

There is a talk about this topic at the next forthcoming Gerrit User Summit 2016 about 100% availability and zero-downtime for Gerrit:

https://gerrit.googlesource.com/summit/2016/+/refs/heads/master/sessions/zero-downtime-upgrade.md

Luca.

On 17 Oct 2016, at 08:19, SeongUk Baek <baeks...@gmail.com> wrote:

Thanks for reply.

Is there any other way for a fail-over?

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[SeongUk Baek]

Dear Luca.

Thank you so much.
I'll check other method for fail-over.

Additionally, could you tell me what is the "transaction coordination"?

[luca.mi...@gmail.com]

Sent from my iPhone

On 20 Oct 2016, at 03:43, SeongUk Baek <baeks...@gmail.com> wrote:

Dear Luca.

Thank you so much.
I'll check other method for fail-over.

Additionally, could you tell me what is the "transaction coordination"?

Look for example at Apache Zookeeper:

http://zookeeper.apache.org/

Thanks a lot in advance

--

[Bassem Rabil]

At Ericsson we use the open source plugin websession_flatfile [1] to avoid having disruptions on end users websessions. Using this plugin we have the master backends sharing the same flatfile for websessions cache. In our case we use the shared storage between masters to store this cache and used from the master backends. For other metadata like secondary index sync, events, and caches coherence between multiple master backends we use 3 open source plugins, i.e. sync-index, sync-events, and evict-cache. The required extensions in Gerrit core for these plugins are included in Gerrit 2.13. For more details you can check this post [2].

[1] https://gerrit.googlesource.com/plugins/websession-flatfile/

[2] https://groups.google.com/forum/#!searchin/repo-discuss/Gerrit$20cluster%7Csort:relevance/repo-discuss/EFgP_wclFlw/-l801OfZEgAJ

Regards

Bassem