| = 28. Recompute mailbox quotas |
| |
| Date: 2020-04-03 |
| |
| == Status |
| |
| Accepted (lazy consensus) |
| |
| == Context |
| |
| JMAP custom quota extension, as well as IMAP https://tools.ietf.org/html/rfc2087[RFC-2087] enables a user to monitor the amount of space and message count he is allowed to use, and that he is effectively using. |
| |
| To track the quota values a user is effectively using, James relies on the link:../site/markdown/server/manage-guice-distributed-james.md#mailbox-event-bus[eventBus] to increment a Cassandra counter corresponding to this user. |
| |
| However, upon Cassandra failure, this value can be incorrect, hence the need of correcting it. |
| |
| == Data model details |
| |
| Table: imapUidTable: Holds mailbox and flags for each message, lookup by message ID |
| |
| Table: messageV2: Holds message metadata, independently of any mailboxes. |
| Content of messages is stored in `blobs` and `blobparts` tables. |
| |
| Table: currentQuota: Holds per quota-root current values. |
| Quota-roots defines groups of mailboxes which share quotas limitations. |
| |
| Operation: |
| |
| * Quota updates are done asynchronously (event bus + listener) for successful mailbox operations. |
| ** If the quota update is not applied, then we are inconsistent |
| ** EventBus errors are retried upon errors, counters being non-indempotent, this can result in inconsistent quotas |
| |
| == Decision |
| |
| We will implement a generic corrective task exposed via webadmin. |
| |
| This task can reuse the `CurrentQuotaCalculator` and call it for each and every quotaRoot of each user. |
| |
| This way, non-Cassandra implementation will also benefit from this task. |
| |
| == Consequences |
| |
| This task is not concurrent-safe. |
| Concurrent operations will result in an invalid quota to be persisted. |
| |
| However, as the source of truth is not altered, re-running this task will eventually return the correct result. |
