Problem
Different application consuming the API’s but the backend has no idea who is consuming it and from where the request coming is from.
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To avoid querying the datastore every time, we can cache custom entities in-memory on the node, so that frequent entity lookups don't trigger a datastore query every time, but happen in-memory, which is much faster and reliable than querying it from the datastore (especially under heavy load).
A. Lazy caching: Cache custom entities in-memory on the node on the first request, so that frequent entity lookups don’t trigger a datastore query every time (only the first time), but happen in-memory. On every first request by a consumer, associated App IDs to requester consumer will be retrieved from datastore and that will be cached, but If there are no APP IDs associated then empty App ID's arrays will be cached.
By doing so it doesn’t matter how many requests the consumer makes, after the first request every lookup will be done in-memory without querying the datastore.
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B. Full table cache on kong service start: Cache the all the records exist in the table on every node immediately after kong service start, so entity lookups don’t trigger a datastore query every time.
- Pros
- No lookup on the data-store except initial so it will help for reducing latency in request response time.
- Cons
- If the database is size is large then the cache and invalidation process will take time.
- Every Node will query datastore after the start of service that will put a load on data-store for some time.
- It will cache the all records even if record not in use and that will unnecessarily increase cache size on every node.
Kong does not seem to have a specific "event" that is broadcasted on startup, so this approach may not be feasible. init_worker is available, but the implementation for that seems complex.
Solution
Kong ENTITY_UPDATED event: This event getting a triggered on kong startup and if any operation made on the entity.
It sends message_t.collection value to nodes (but it's getting trigged after every 30sec) on kong startup and plugin name if it is triggered after operation made on the particular plugin entity.
local function invalidate_on_update(message_t)
if message_t.collection == "nodes" then
local cachesetflag = cache.get("appids.cacheset");
if cachesetflag == false
// Read the appid and consumer mapping and cache it
end
// Set cache flag
cache.set("appids.cacheset", true);
end
end
[events.TYPES.ENTITY_UPDATED] = function(message_t)
invalidate_on_update(message_t)
end
Cache Storage
The cache will be stored in the key-value pair where the key will be 'appid'.consumer_id and value will be an array of APP ids.
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