This gem handles remote templates - fetching via http and caching the result locally in the process (first cache level), as well as in a redis instance (second cache level), as well as fallback handling if an error was encountered during the fetching of the template.
The caches obviously allow faster access to the fetched result, where the second level redis cache allows a centralized, authoritative result to be shared between multiple server processes.
By default, the process-local cache will be refreshed from the redis cached result every 60 seconds (configurable).
If an error was encountered during the fetching of the template via http, the library will fall back onto a configurable default template to serve, which will be refreshed after a configurable timeout.
Once a template has been fetched successfully, it will not time out or be re-fetched. To fetch the template anew, the redis cache entry needs to be removed, which will trigger a new http fetch the next time the first level cache will be refreshed from the second level cache.
The following options can be set on the class in a config/initializer/ file:
RedisTemplateResolver.default_template-
mandatory Body of the default template to use if the remote template cannot be retrieved. Note that this is the actual template, not the path to a template file.
RedisTemplateResolver.redis_connector-
mandatory The redis connector to use for storing templates in the second level cache. Note that this is an already configured instance of Redis, not the connection parameters.
RedisTemplateResolver.local_cache_ttl-
The number of seconds between refreshing the in-process cache from redis (defaults to 60).
RedisTemplateResolver.local_cache_negative_ttl-
The number of seconds to wait before retrying to fetch the template via http, if anything went wrong (defaults to 10).
RedisTemplateResolver.http_timeout-
Seconds to wait for the fetch via http to complete (defaults to 5 seconds).
RedisTemplateResolver.template_handler_name-
Name of the template handler that should render the fetched template (defaults to “erb”).
Create a class that derives from RedisTemplateResolver.
This class must override the following method: lookup_template_url. The method will receive the name of the template to be retrieved in +@template_name+ and should return a full URL to the template.
Optionally the following two methods can also be overridden:
- +postprocess_template( template_body )+
-
Called right after successfully retrieving the template file, which is passed in as an argument. The method should return the template body to be actually stored and used. If you want to perform sanity checks on the returned template, you can raise an
TemplateRejectedErrorexception, which will refuse the retrieved template and pretend that template retrieval failed. - +resolver_guard( name, prefix, partial, details)+
-
If this method is present and returns false or nil, Redis Template Resolver will not handle this template. Return true to process the template resolution with this library.
In your application controller, add the following line:
append_view_path MyRedisTemplateResolver.new
where MyRedisTemplateResolver is the name of the class that derives from the RedisTemplateResolver class. Supply a template name with a prefix of “redis:” to route the lookup request to the redis template resolver.
E.g. to fetch your layouts via http, use the following:
layout lambda { |args| "redis:some_template_name}" }