Question 1

How do I expose Go functions to WebAssembly plugins with Extism?

Accepted Answer

Use extism.NewHostFunctionWithStack to define Go functions, then pass them in the NewPlugin call. The README shows an example with kv_read and kv_write functions that handle memory reads and writes via CurrentPlugin methods.

Question 2

Extism Go SDK vs HashiCorp go-plugin: which should I use?

Accepted Answer

Extism is best for cross-language, sandboxed WebAssembly plugins with security benefits, while go-plugin suits pure Go plugins with direct binary communication. Choose Extism for multi-language support and isolation, go-plugin for Go-native performance.

Question 3

How to handle state persistence in Extism plugins?

Accepted Answer

Plugins can maintain internal state across calls using variables, as shown in the count_vowels example where 'total' persists. For external state, implement host functions to interact with databases or KV stores.

Question 4

What's the performance overhead of using Extism WebAssembly plugins?

Accepted Answer

Overhead includes Wasm initialization and host function calls, but it's mitigated by pre-compilation and caching. The README details using Wazero's compilation cache to speed up subsequent plugin instances.

Question 5

How to pass custom configuration to an Extism plugin in Go?

Accepted Answer

Set the Config map in the Manifest with key-value pairs, which are passed statically at initialization. The example modifies the 'vowels' config to change character sets in the count_vowels plugin.

Question 6

Can Extism plugins access the host filesystem?

Accepted Answer

Yes, by mapping host directories via AllowedPaths in the Manifest, as demonstrated with a data directory linked to /mnt in the Wasm runtime, but plugins must be compiled with WASI support.

Extism Go SDK

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