Support opt-in psrpc bus compression

[paulwe]

psrpc v0.7.6 (psrpc#130) added opt-in gzip at the bus boundary, and protocol#1771 surfaced it as rpc.PSRPCConfig.Compression with a BusOptions() conversion. runService built the bus from the redis client alone, so there was no way to reach the setting.

psrpc:
  compression:
    quality: 6
    threshold: 1024
    max_decompressed_size: 0

Shape

Ingress carried no rpc.PSRPCConfig at all, only a top-level psrpc_skip_claim bool, so this adds the whole block under a psrpc: key. That matches the layout livekit-server uses (livekit#4844) and gives egress and SIP a shape to copy — neither has done this yet.

It is seeded in NewConfig rather than InitDefaults, because the handler subprocess parses its config with initialize=false. Without the seed, a config setting only quality would leave Threshold at zero and compress every payload, however small.

The service process holds the only bus. The per-session handler subprocess talks to the parent over unix-socket gRPC IPC and never builds one, so nothing else needed threading. The integration suite bypasses NewConfig, so GetDefaultConfig carries the same seed.

Compression is off by default

A peer on psrpc older than v0.7.6 ignores the compression marker — psrpc deserializes with DiscardUnknown — and then decodes the gzipped bytes as the payload, so the message is dropped without an error. livekit-server, egress, SIP and agent workers share this bus, so enabling it is a two-stage operator action: roll v0.7.6+ everywhere, then raise quality at the publishers. The README says so at the setting.

max_decompressed_size only affects reading, so it can be set ahead of quality.

Testing

pkg/config/config_test.go is new; the package had no tests. It covers the defaults and an override that leaves Threshold at its default.

Verified the config actually reaches the compressor with a throwaway psrpc echo RPC over a local bus: the default config round-trips, quality: 6 with threshold: 1 round-trips, and adding max_decompressed_size: 64 drops that same 16 KB payload — which is what proves it was gzipped rather than skipped by the threshold. quality: 0 with the same cap delivers it.

Not verified against a live livekit-server; that needs a peer already on psrpc v0.7.6+.

Note on the protocol pin

v1.51.1-0.20260905133529-a4f4b5c0c23f is protocol main at the #1771 merge, the same pseudo-version livekit#4844 uses. It is 14 commits ahead of the previous pin and otherwise additive.

[devin-ai-integration]

✅ Devin Review: No Issues Found

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