Scaling based on a number of active calls fixed and filtering by sipTrunkId

[rafallezanko]

There was existing TODO to fix -> Scale outbound calls based on number or active calls.

Load-aware affinity routing and trunk whitelisting for SIP bridges

Summary

• Implement CreateSIPParticipantAffinity to return a dynamic score based on the number of active calls (inbound + outbound),
  replacing the hardcoded 0.5. This enables psrpc to route new outbound calls to the least-loaded SIP bridge.
• Add sip_trunk_ids config option to restrict a SIP bridge to only serve specific trunk IDs, enabling dedicated gateways per
  trunk.

Affinity algorithm

The function evaluates in order:

1. Trunk whitelist (sip_trunk_ids) — if configured and the request's trunk ID is not in the list, return 0 immediately (this node
   will not claim the call).
2. Capacity limit (max_active_calls) — if configured, return 1 - (active / max). Returns 0 when at or over capacity.
3. Fallback (no max_active_calls) — return 1 / (1 + active). No hard cap, but nodes with fewer calls are always preferred.

Configuration

Optional: maximum number of concurrent calls this bridge should handle.
Affinity scales linearly from 1.0 (idle) to 0.0 (at capacity).
max_active_calls: 100

Optional: only accept outbound calls for these trunk IDs.
Calls for any other trunk will get affinity 0 (routed elsewhere).
If empty/unset, all trunks are accepted.
sip_trunk_ids:
- "ST_abc123"
- "ST_def456"

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 63.07%. Comparing base (0460b40) to head (cfd3770).
⚠️ Report is 234 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/sip/service.go	87.50%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #598      +/-   ##
==========================================
- Coverage   65.25%   63.07%   -2.18%     
==========================================
  Files          51       35      -16     
  Lines        6588     6920     +332     
==========================================
+ Hits         4299     4365      +66     
- Misses       1915     2128     +213     
- Partials      374      427      +53     

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[rafallezanko]

Hi @dennwc are you able to review this change? Or call someone who can :) Thank you!

[alexlivekit]

Didn't look too deep into this one, but overall lgtm

[rafallezanko]

Hi @alexlivekit, thank you! How does merging to main work for this repository? Will you merge? When do you have a plan to release a new version of SIP bridge?

Thank you :)

[rafallezanko]

Hi @alexlivekit, thank you! How does merging to main work for this repository? Will you merge? When do you have a plan to release a new version of SIP bridge?

Thank you :)

Hi @alexlivekit @dennwc can you have a look at the comment please?

[dennwc]

LGTM! Apologies for the delay on our end.

[rafallezanko]

Great, thank you for merging! Do you have any release timeline for this project?

[alexlivekit]

@rafallezanko , no immediate plans for releases as I understand. I'll ask around just in case.

On another note, related to this PR, this change in protocol actually drops the usage of this affinity function altogether. It is not yet propagated anywhere, but for future reference please make sure to use an appropriate version or a patched version that re-enabled this use.