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63 lines
2.3 KiB
ReStructuredText
63 lines
2.3 KiB
ReStructuredText
.. _limits:
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Limits
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------
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Locmem
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......
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Locmem is a just a dict stored in a single Python process.
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It’s not shared between processes, so don’t use locmem with django-cachalot
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in a multi-processes project, if you use RQ or Celery for instance.
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Redis
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.....
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By default, Redis will not evict persistent keys (those without an expiry set)
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when the maximum memory has been reached. The keys created by django-cachalot
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are persistent, so in an out of memory situation most of the site will go down
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due to OOM exceptions.
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To avoid this, you can change 'maxmemory-policy' to 'allkeys-lru' in redis.conf.
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Be aware that this policy applies to all the databases on that server.
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You'll also want to keep an eye on the redis stats and increase 'maxmemory' if
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needed. This is just to improve performance, it doesn't impact site availability.
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MySQL
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.....
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This database software already provides by default something like
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django-cachalot:
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`MySQL query cache <http://dev.mysql.com/doc/refman/5.7/en/query-cache.html>`_.
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Django-cachalot will slow down your queries if that query cache is enabled.
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If it’s not enabled, django-cachalot will make queries much faster.
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But you should probably better enable the query cache instead.
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.. _Raw queries limits:
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Raw SQL queries
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...............
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.. note::
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Don’t worry if you don’t understand what follow. That probably means you
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don’t use raw queries, and therefore are not directly concerned by
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those potential issues.
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By default, django-cachalot tries to invalidate its cache after a raw query.
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It detects if the raw query contains ``UPDATE``, ``INSERT`` or ``DELETE``,
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and then invalidates the tables contained in that query by comparing
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with models registered by Django.
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This is quite robust, so if a query is not invalidated automatically
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by this system, please :ref:`send a bug report <reporting>`.
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In the meantime, you can use :ref:`the API <API>` to manually invalidate
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the tables where data has changed.
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However, this simple system can be too efficient in some cases and lead to
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unwanted extra invalidations.
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In such cases, you may want to partially disable this behaviour by
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:ref:`dynamically overriding settings <Dynamic overriding>` to set
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:ref:`CACHALOT_INVALIDATE_RAW` to ``False``.
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After that, use :ref:`the API <API>` to manually invalidate the tables
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you modified.
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