Documentation
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Overview ¶
Package memlimit resolves the memory this process may actually use, so the module's engine-wide ceilings can be derived from the smallest bound that is observable rather than from a constant chosen without knowledge of the host.
Why a library must not simply set GOMEMLIMIT ¶
GOMEMLIMIT is process-global state and belongs to the embedder: a library that sets it silently changes the GC behaviour of an application that may have many other components. So this package only ever READS a limit, and the module uses what it reads to lower its OWN ceilings. Setting GOMEMLIMIT remains the right move for a program — the ggserver binary — and the wrong move here.
Why the constants were not enough (rmp #2421) ¶
The engine-wide ceilings landed by the 2026-08-10 certification are finite, and that closed a real denial-of-service hole. But they are FIXED: 4 GiB of results and 1 GiB of inbound decode, applied whenever the process has no Go soft memory limit to derive from — which is the default state of every Go process. Inside a container capped below those numbers the ceiling is larger than the whole container, so it cannot bind before the kernel's OOM killer does, and the failure mode is a killed process rather than a typed error. That is the opposite of the graceful degradation the module promises.
It is not a theoretical concern: a 4M-relationship Cypher load was OOM-killed in an 8 GB container on 2026-08-11 ("Killed process (ggserver) anon-rss:8370788kB"), and re-running the identical fixture with GOMEMLIMIT=6GiB completed at 4520 MB. The cap was the missing input, not the workload.
Memgraph solves the same problem by reading the host: its global memory limit defaults to 100% of physical memory with swap and 90% without, via utils::sysinfo::InstalledMemory (src/flags/memory_limit.cpp:20-38, v3.9.0). The shape adopted here is the same — derive from what is observable — while the magnitudes stay this module's own.
Index ¶
Constants ¶
This section is empty.
Variables ¶
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Functions ¶
func Available ¶
Available returns the smallest observable bound, in bytes, on the memory this process may use, and whether one was found at all.
The sources are consulted in order of authority:
- the Go soft memory limit, when the embedder has set one (GOMEMLIMIT or runtime/debug.SetMemoryLimit) — an explicit statement of intent;
- the cgroup v2 memory.max of the process's own cgroup;
- the cgroup v1 memory.limit_in_bytes.
It deliberately does NOT fall back to installed RAM. A bound this package cannot vouch for is worse than no bound: the caller's own finite constant is the documented last resort, and reporting false here selects it.
The answer is computed ONCE and cached: it is consulted while constructing an engine or a server, never on a query path, and the underlying limit cannot change for a running process in the cases that matter.
Safe for concurrent use.
func ResolveCount ¶
func ResolveCount() int64
ResolveCount reports how many times the underlying lookup has run. It exists for the test that pins the once-per-process contract.
Types ¶
This section is empty.
Source Files