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971d497c1e
ref https://linear.app/tryghost/issue/ENG-1543/debounce-the-members-lastseenatupdater - The `LastSeenAtUpdater.updateLastSeenAt` function is called in response to a `MemberClickEvent` — when a member clicks a link in an email with tracking enabled. This function can be called many times for the same member in a short period of time if e.g. a link checker is clicking all the links in an email they received. - This function should only update a member's `last_seen_at` timestamp once per day. To accomplish this, `updateLastSeenAt` runs a `select...for update` query to find the member's current `last_seen_at` timestamp, and only updates the timestamp if the current `last_seen_at` is before the start of the current day. The `for update` is required to avoid a race condition, which previously caused this function to update the `last_seen_at` timestamp more frequently than needed, which results in many unnecessary database queries. However, we still run the initial `select...for update` query for each event, which seems to be resulting in contention for locks on the member's row in the `members` table. - This commit introduces a simple in-memory cache so that we avoid calling `updateLastSeenAt` if the member's `last_seen_at` timestamp has already been updated in the current day, which should avoid running so many `select...for update` queries and locking the `members` table up. |
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| .. | ||
| EventStorage.js | ||
| index.js | ||
| LastSeenAtCache.js | ||
| LastSeenAtUpdater.js | ||