DIcom Server with mysql-error-with-the-database-engine-code

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21

Great, thanks for the feedback!

Note that no official binary release is currently planned, as I’m focused on some high-priority projects.

The release should hopefully be available by July.

Regards,
Sébastien-

22

Regarding official image, I am ok with that since I am compiling the code locally. I do have a follow up question. My eventual deployment goal is to get Orthanc (with MySQL plugin) cluster with multi-writer capabilities.

I understand that Orthanc project official support Postgres-Plugin and Postgres-Plugin today is multi-writer capable.

My question is – What would it take to make MySQL plugin multi-writer capable. Is there list of issues (or some notes) from Postgres development for this activity? Any other document/discussion that can help me understand scope for this activity (what problems needs to be solved)?

23

Hi,

Actually, there are currently 2 issues that needs to be solved in order to handle multiple writers correctly:

Additionally, we should probably clearly identify all transactions as (READ or READ/WRITE) in order to minimize the conflicts in transactions.

This requires some changes in the Core of Orthanc and in the DB plugins so it’s unfortunately not a quick fix …

Best regards,

Alain.

24

Hi Alain,
Thanks for response. Since you are referring to changes in Orthanc core for multi-writer support, does this imply that even Postgres plugin doesn’t support multiple-writer capability?

When I use MySQL plugin with Orthanc, I get following log which indicates that MySQL plugin does not support multi-writer capability. I do not see this log with Postgres Plugin. From this I inferred that Postgres Plugin is multi-writer capable. But your comment about lack of support in Orthanc core doesn’t align with this conclusion.

orthanc_1 | W0503 00:44:45.989042 OrthancPluginDatabase.cpp:330] Your database index plugin is not compatible with multiple Orthanc writers

Can you explain overall status of multi-writer capability in Orthanc-core and Orthanc-plugins? If Orthanc-core functionality is implemented (in future), would all DB-plugins inherit this or do you foresee additional plugin specific effort?

25

Hello,

We never claimed that the PostreSQL and MySQL plugins currently support multi-writer capability (NB: For future reference, as of writing, Orthanc is at release 1.5.6, PostgreSQL 3.2, and MySQL 2.0).

The log entry you report is about, well, a work-in-progress for our internal purpose. Osimis has validated the “single writer, multiple readers” scenario, provided the “SaveJobs” configuration option is set to “false” (check out the comments in the configuration file).

That being said, nothing prevents Orthanc from supporting the “multiple writers” scenario. This can be done in a few days/weeks of work, for which we need financial support from the industry or from hospitals, as this is clearly an enterprise-related use case.

The required (non-trivial) modifications would essentially be in the Orthanc core and in the Orthanc plugin SDK. From the perspective of the plugins, the modification would essentially boils down to creating SQL transactions using either “START TRANSACTION READ ONLY” or “START TRANSACTION READ WRITE”, depending on the input from the Orthanc plugin SDK.

Sébastien-

26

Hi Sébastien,
Thanks for clarifying the present status of multi writer support. This information is really useful.