Wasm runtime

The following runtimes are supported by Envoy:

Name	Description
envoy.wasm.runtime.v8	V8-based runtime
envoy.wasm.runtime.wamr	WAMR runtime
envoy.wasm.runtime.wasmtime	Wasmtime runtime
envoy.wasm.runtime.null	Compiled modules linked into Envoy

WAMR(WASM-Micro-Runtime), Wasmtime runtime is not included in Envoy release image by default.

Wasm runtime emits the following statistics:

Name	Type	Description
wasm.<runtime>.created	Counter	Total number of execution instances created
wasm.<runtime>.active	Gauge	Number of active execution instances
wasm.<runtime>.memory_size	Gauge	Total linear memory size in bytes of all active execution instances. Wasm linear memory never shrinks, so an instance’s share only drops when it is destroyed. Not reported for the null runtime
wasm.wasm_vm_count	Gauge	Process-wide number of active Wasm VMs, across every runtime

Each Wasm plugin also emits the following statistics, where <name> is the plugin name:

Name	Type	Description
wasm.<name>.vm_reload_backoff	Counter	Number of reloads of a failed execution instance skipped because of the reload backoff, with the FAIL_RELOAD failure policy
wasm.<name>.vm_reload_success	Counter	Number of successful reloads of a failed execution instance, with the FAIL_RELOAD failure policy
wasm.<name>.vm_reload_failure	Counter	Number of failed reloads of a failed execution instance, with the FAIL_RELOAD failure policy
wasm.<name>.vm_memory_size	Gauge	Sum of the linear memory size in bytes of the per-worker execution instances serving the plugin. Not reported for the null runtime

Each worker thread runs its own execution instance of a plugin, with its own linear memory, so the instances of a plugin on different workers can have different sizes. wasm.<name>.vm_memory_size adds up the instances of all workers, each sampled the last time the plugin was used on that worker (e.g. for a request). Plugins with the same vm_config share their instances, so each of them reports the full size of the shared instances, and the sum over plugins can exceed wasm.<runtime>.memory_size. wasm.<runtime>.memory_size counts every instance once, including the ones that serve no requests, and is the total memory used by the runtime.