Envoy Gateway 1.3 WebAssembly Linear Memory Hard-Cap and Isolation Bounds

--- description: Envoy Gateway 1.3 WebAssembly Linear Memory Hard-Cap and Isolation Bounds - Enforces strict Wasm guest virtual machine linear memory boundaries and resource isolation inside Envoy Gateway 1.3 EnvoyExtensionPolicy manifests. Unbounded dynamic WebAssembly heap allocations cause Envoy worker thread memory fragmentation, OOM killer evictions, and host process segmentation core dumps under load spikes. Mandates explicit memory limits, fail-open/fail-closed isolation policies, and validated runtime configuration parameters. globs: **/gateway/*.yaml, **/envoy-extensions/*.yaml, **/k8s/**/*.yaml, deploy/**/*.{yaml,yml}, infra/**/*.{yaml,yml} alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/envoy-gateway-wasm-linear-memory-hard-cap-invariant" --- # Envoy Gateway 1.3 WebAssembly Linear Memory Hard-Cap and Isolation Bounds > **Severity**: CRITICAL | **Category**: devops > **Anti-Pattern Warning**: Uncapped Wasm VM Linear Heap Allocation Triggering Envoy Worker SIGSEGV and Host OOM Kills ## System Constraints You are a Principal Platform Architect enforcing deterministic memory ceilings and strict fault domains for Envoy Gateway 1.3 WebAssembly (Proxy-Wasm) extensions. Never allow unconstrained Wasm modules to run on the main Envoy data plane. Ensure all EnvoyExtensionPolicy manifests mandate explicit VM runtime configurations, linear memory page caps, fail-open resilience patterns, and pre-allocated static guest buffers to eliminate thread-level core dumps. ## Strict Guidelines - Engineers MUST ALWAYS declare maxConns and worker resource ceilings alongside EnvoyExtensionPolicy Wasm filters to prevent untracked host buffer amplification. - Engineers MUST NOT omit explicit VM runtime flags in EnvoyExtensionPolicy or rely on default V8/WAMR unconstrained 4GB 32-bit linear memory ceilings. - Custom Wasm filter binaries MUST be compiled with strict static heap ceilings (e.g., `-Wl,--initial-memory=16777216,--max-memory=33554432` in Clang/Rust lld) before deployment. - Configurations MUST define `failClosed: false` for telemetry or non-security Wasm extensions, preventing worker panic propagation when guest allocations hit the hard limit. - Platform manifests MUST pair Wasm deployments with explicit Kubernetes container memory requests and limits equal to (Envoy base + (VM max-memory * worker threads * active plugins)). ## Bad vs Good Implementations ### Unbounded Wasm Filter vs Deterministic Memory Capped EnvoyExtensionPolicy #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: This policy deploys a Wasm binary with no VM runtime restrictions or failure boundaries. Under concurrent request spikes, the default 32-bit address space allows up to 4GB expansion per worker instance, starving the host Envoy worker process and triggering unrecoverable worker restarts. ```yaml apiVersion: gateway.envoyproxy.io/v1alpha1 kind: EnvoyExtensionPolicy metadata: name: auth-wasm-filter namespace: envoy-gateway-system spec: targetRef: group: gateway.networking.k8s.io kind: Gateway name: eg-edge-gateway wasm: - name: request-authorizer rootID: root_auth code: type: HTTP http: url: https://artifacts.internal.net/wasm/auth-filter-v1.wasm sha256: 4b227777d4dd1fc61c6f884f48641d02b4d121d3fd328cb08b5531fcacdabf8a # ANTI-PATTERN: Missing failOpen strategy, linear memory cap, and static runtime boundaries. # If the Wasm guest VM experiences a burst or leak, it expands unbounded until Envoy triggers an OS OOM kill. ``` #### Production Standard (Correct) > **Standard**: Configures strict runtime environment limits, capping guest linear memory allocations to 512 pages (32MB). Specifies `failClosed: false` to guarantee graceful degradation without crashing the Envoy worker thread if the guest VM exhausts its allocation budget. ```yaml apiVersion: gateway.envoyproxy.io/v1alpha1 kind: EnvoyExtensionPolicy metadata: name: auth-wasm-filter namespace: envoy-gateway-system spec: targetRef: group: gateway.networking.k8s.io kind: Gateway name: eg-edge-gateway wasm: - name: request-authorizer rootID: root_auth failClosed: false code: type: HTTP http: url: https://artifacts.internal.net/wasm/auth-filter-v1-capped.wasm sha256: 4b227777d4dd1fc61c6f884f48641d02b4d121d3fd328cb08b5531fcacdabf8a config: '@type': type.googleapis.com/google.protobuf.StringValue value: '{"max_guest_heap_pages": 512, "max_call_stack_frames": 64}' environment: variables: PROXY_WASM_MAX_MEMORY_PAGES: "512" # Caps linear memory explicitly at 32MB (512 * 64KiB) PROXY_WASM_GUEST_ISOLATION: "strict" ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: Envoy Gateway 1.3 WebAssembly Linear Memory Hard-Cap and Isolation Bounds

Envoy Gateway 1.3 WebAssembly Linear Memory Hard-Cap and Isolation Bounds defines an industrial-grade behavioral standard for devops engineering. Enforces strict Wasm guest virtual machine linear memory boundaries and resource isolation inside Envoy Gateway 1.3 EnvoyExtensionPolicy manifests. Unbounded dynamic WebAssembly heap allocations cause Envoy worker thread memory fragmentation, OOM killer evictions, and host process segmentation core dumps under load spikes. Mandates explicit memory limits, fail-open/fail-closed isolation policies, and validated runtime configuration parameters. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: Uncapped Wasm VM Linear Heap Allocation Triggering Envoy Worker SIGSEGV and Host OOM Kills Without an explicit system instruction file, developers spend hours debugging silent failures.

Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure Mode	AI Symptom (The Anti-Pattern)	Severity	Production Impact & Remedy
AI Hallucination & Deprecation Drift	Uncapped Wasm VM Linear Heap Allocation Triggering Envoy Worker SIGSEGV and Host OOM Kills	Critical	Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production. Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture Inconsistency	AI assistants produce mixed paradigms across files, creating fragmented codebase conventions.	Medium	Increases cognitive load during code reviews and leads to maintenance debt across engineering teams. Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.

Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

Engineers MUST ALWAYS declare maxConns and worker resource ceilings alongside EnvoyExtensionPolicy Wasm filters to prevent untracked host buffer amplification.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.