Important
This release contains important fixes which address resource utilization regressions which impacted Router v1.59.0 and v1.59.1. These regressions were in the form of:
- A small baseline increase in memory usage; AND
- Additional per-request CPU and memory usage for queries which included references to abstract types with a large number of implementations
If you have enabled Distributed query plan caching, this release contains changes which necessarily alter the hashing algorithm used for the cache keys. On account of this, you should anticipate additional cache regeneration cost when updating between these versions while the new hashing algorithm comes into service.
🐛 Fixes
Improve performance of query hashing by using a precomputed schema hash (PR #6622)
The router now uses a simpler and faster query hashing algorithm with more predictable CPU and memory usage. This improvement is enabled by using a precomputed hash of the entire schema, rather than computing and hashing the subset of types and fields used by each query.
For more details on why these design decisions were made, please see the PR description
By @IvanGoncharov in #6622
Fix increased memory usage in sysinfo since Router 1.59.0 (PR #6634)
In version 1.59.0, Apollo Router started using the sysinfo crate to gather metrics about available CPUs and RAM. By default, that crate uses rayon internally to parallelize its handling of system processes. In turn, rayon creates a pool of long-lived threads.
In a particular benchmark on a 32-core Linux server, this caused resident memory use to increase by about 150 MB. This is likely a combination of stack space (which only gets freed when the thread terminates) and per-thread space reserved by the heap allocator to reduce cross-thread synchronization cost.
This regression is now fixed by:
- Disabling
sysinfo’s use ofrayon, so the thread pool is not created and system processes information is gathered in a sequential loop. - Making
sysinfonot gather that information in the first place since Router does not use it.
By @SimonSapin in #6634