Mercurial > hg > orthanc-book
comparison Sphinx/source/faq/scalability.rst @ 752:9b8fb1b37638
added notes about concurrency
| author | Sebastien Jodogne <s.jodogne@gmail.com> |
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| date | Sun, 15 Aug 2021 13:36:07 +0200 |
| parents | b2b1ba11faaa |
| children | 4e9dc26a5cb9 |
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| 308 * If a higher-level application **modifies metadata and/or | 308 * If a higher-level application **modifies metadata and/or |
| 309 attachments** in the presence of multiple writers, Orthanc provides | 309 attachments** in the presence of multiple writers, Orthanc provides |
| 310 a :ref:`revision mechanism <revisions>` to prevent concurrent | 310 a :ref:`revision mechanism <revisions>` to prevent concurrent |
| 311 updates. | 311 updates. |
| 312 | 312 |
| 313 * Each Orthanc instance maintains its own list of jobs; therefore, the | 313 * Thanks to this support of concurrent accesses, it is possible to put |
| 314 ``/jobs`` route will return only the jobs of the responding Orthanc. | 314 a **load balancer** on the top of the REST API of Orthanc. All the |
| 315 | 315 DICOM resources (patients, studies, series and instances) are indeed |
| 316 shared by all the instances of Orthanc connected to the same | |
| 317 underlying database. As an application, this might be of great help | |
| 318 if multiple viewers must connect to Orthanc. In `Kubernetes | |
| 319 <https://kubernetes.io/>`__, concurrent accesses also make it | |
| 320 possible to manage a set of replicas of Orthanc (e.g. as `deployment | |
| 321 <https://kubernetes.io/docs/concepts/workloads/controllers/deployment/>`__). | |
| 322 | |
| 323 There are however some caveats if using a load balancer or | |
| 324 Kubernetes replicas, notably: | |
| 325 | |
| 326 - Each Orthanc instance maintains its own list of jobs. Therefore, | |
| 327 the ``/jobs`` route will return only the jobs of the responding | |
| 328 Orthanc. | |
| 329 | |
| 330 - The ``/modalities`` or the ``/peers`` are also private to each | |
| 331 instance of Orthanc in the cluster, as soon as the respective | |
| 332 options ``DicomModalitiesInDatabase`` and | |
| 333 ``OrthancPeersInDatabase`` are set to ``true``. | |
| 334 | |
| 335 If you need to use such primitives in your application, you have | |
| 336 three possibilities: (1) Introduce a distinguished Orthanc server | |
| 337 that is responsible to take care of all the jobs (including | |
| 338 modalities and peers), (2) create an :ref:`Orthanc plugin <plugins>` | |
| 339 (e.g. using :ref:`Python <python-plugin>`) that queries all the | |
| 340 Orthanc in the cluster and that aggregates all of their answers, | |
| 341 or (3) do the same using a higher-level framework (such as Node.js). | |
| 342 | |
| 316 | 343 |
| 317 Latency | 344 Latency |
| 318 ^^^^^^^ | 345 ^^^^^^^ |
| 319 | 346 |
| 320 For some queries to the database, Orthanc performs several small SQL | 347 For some queries to the database, Orthanc performs several small SQL |