Add proposals for client-identity rate limiting (write and query paths)#7681
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krunaljain wants to merge 8 commits into
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Add proposals for client-identity rate limiting (write and query paths)#7681krunaljain wants to merge 8 commits into
krunaljain wants to merge 8 commits into
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July 10, 2026 11:10
Cortex's ingestion and query rate limits are enforced at the tenant level only. When multiple independent services or teams share a tenant, one noisy or misbehaving client can exhaust the whole tenant's budget for everyone else, and there is no way to distinguish who, within a tenant, is responsible. Adds two companion design proposals: - client-identity-rate-limiting.md: write-path (distributor) enforcement, keyed on a new trusted X-User-ID header, following the same trust model Cortex already uses for X-Scope-OrgID. - client-identity-query-rate-limiting.md: the read-path (query-frontend) follow-on, reusing the same header and identity approach. Both are opt-in, additive to existing limits, and covered as experimental features on the proposed rollout plan. Signed-off-by: Krunal Jain <kjain25@apple.com>
Both proposals now specify global enforcement (dividing the per-client limit across healthy replicas via the existing ring/distributor-count mechanism) rather than local-only with global as a follow-up. - Write path: rename section 'Local enforcement is less precise' -> 'Global enforcement'; update enforcement description and rollout plan - Query path: rename section 'Local enforcement precision...' -> 'Global enforcement and interaction with the results cache'; update frontend/scheduler-split section, rate-limiter description, rollout plan, and open-questions cross-reference Signed-off-by: Krunal Jain <kjain25@apple.com>
The previous commit said 'global enforcement' but implied Cortex's existing divide-by-replica-count approximation. This updates both proposals to describe the intended gossip-based mechanism: - Each replica tracks a local per-client counter - Counters are gossiped to peers via the existing memberlist transport - Enforcement is against the cluster-wide sum, not a per-replica share This is more accurate than divide-by-N: it handles uneven load distribution and replica count changes without reconfiguration. The gossip convergence lag (order of memberlist gossip interval) is noted as an acceptable property of this best-effort limit. Signed-off-by: Krunal Jain <kjain25@apple.com>
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Thanks!. I have a couple of suggestions/questions
…enforcement design - Replace 'global enforcement via gossip' with ring-based distributed enforcement: shard (tenant, client) onto the existing ring so one replica owns the authoritative counter per key; works on any ring backend (Consul/Etcd/memberlist), not memberlist-only. - Rename 'global' counter language throughout both proposals to 'distributed per-tenant' to avoid confusion with cross-tenant scope. - Move tracked_clients_limit from a process-wide cap to a per-tenant override, consistent with every other Cortex limit. - Clarify LRU eviction semantics under rate limiting: eviction resets a client's counter (allowing a brief burst), which is the intentional tradeoff over refusing new clients when the cap is full. Signed-off-by: Krunal Jain <kjain25@apple.com>
Add many parallel agent instances fanning out under one shared tenant to the list of scenarios that motivate client-identity rate limiting, alongside the existing bad-config/retry-storm/deployment examples. Signed-off-by: Krunal Jain <kjain25@apple.com>
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Thanks for addressing the comments. Here are more thoughts/comments
CharlieTLe
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July 21, 2026 12:50
Addresses review feedback: X-Scope-ClientID keeps the X-Scope- prefix consistent with X-Scope-OrgID while avoiding collision with the already-defined-but-dormant X-Scope-UserID header. Also fixes a leftover cross-reference to a renamed section, and corrects box-drawing alignment in the ASCII diagrams. Signed-off-by: Krunal Jain <kjain25@apple.com>
…Limiting Disambiguates from the companion Client-Identity Query Rate Limiting proposal, per review feedback. Signed-off-by: Krunal Jain <kjain25@apple.com>
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Renames the file and slug to client-identity-ingestion-rate-limiting to match the "Client-Identity Ingestion Rate Limiting" title, and updates the two cross-references in the companion query-path proposal. Signed-off-by: Krunal Jain <kjain25@apple.com>
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What this PR does
Adds two companion design proposals to
docs/proposals/:client-identity-rate-limiting.md: proposes a second, optional rate-limiting dimension below the tenant on the write (ingestion) path, keyed on a new trustedX-User-IDheader, following the same trust model Cortex already uses forX-Scope-OrgID.client-identity-query-rate-limiting.md: a companion follow-on applying the same identity mechanism to query-frontend rate limiting on the read path.Motivation
Cortex enforces ingestion and query limits at the tenant level only. In practice a single tenant is often shared by multiple independent services or teams, and today's limiters cannot distinguish a well-behaved writer/querier from a noisy or misbehaving one sharing the same
X-Scope-OrgID. These proposals add an opt-in, additive mechanism to throttle by client identity below the tenant, without changing existing tenant-level behavior for anyone who doesn't configure it.Both proposals are:
Design highlights
X-User-IDheader, trusted the same way Cortex already trustsX-Scope-OrgID(i.e. no new authentication mechanism is introduced).Status
Both are filed as proposals for discussion (
Status: Proposed). No code changes are included in this PR; implementation would follow as separate PRs once the design is reviewed.Checklist