| # 12. Projections for JMAP Messages |
| |
| Date: 2019-10-09 |
| |
| ## Status |
| |
| Accepted (lazy consensus) & implemented |
| |
| ## Context |
| |
| JMAP core RFC8620 requires that the server responds only properties requested by the client. |
| |
| James currently computes all of the properties regardless of their cost, and if it had been asked by the client. |
| |
| Clearly we can save some latencies and resources by avoiding reading/computing expensive properties that had not been explicitly requested by the client. |
| |
| ## Decision |
| |
| Introduce two new datastructures representing JMAP messages: |
| - One with only metadata |
| - One with metadata + headers |
| |
| Given the properties requested by the client, the most appropriate message datastructure will be computed, on top of |
| existing message storage APIs that should remain unchanged. |
| |
| Some performance tests will be run in order to evaluate the improvements. |
| |
| ## Consequences |
| |
| GetMessages with a limited set of requested properties no longer result necessarily in full database message read. We |
| thus have a significant improvement, for instance when only metadata are requested. |
| |
| Given the following scenario played by 5000 users per hour (constant rate) |
| - Authenticate |
| - List mailboxes |
| - List messages in one of their mailboxes |
| - Get 10 times the mailboxIds and keywords of the given messages |
| |
| We went from: |
| - A 20% failure and timeout rate before this change to no failure |
| - Mean time for GetMessages went from 27 159 ms to 27 ms (1000 time improvment), for all operation from |
| 27 591 ms to 60 ms (460 time improvment) |
| - P99 is a metric that did not make sense because the initial simulation exceeded Gatling (the performance measuring tool |
| we use) timeout (60s) at the p50 percentile. After this proposal p99 for the entire scenario is of 1 383 ms |
| |
| ## References |
| |
| - /get method: https://tools.ietf.org/html/rfc8620#section-5.1 |
| - [JIRA](https://issues.apache.org/jira/browse/JAMES-2919) |
| * [PR discussing this ADR](https://github.com/apache/james-project/pull/170) |
