feat(server,mcp): add systemd watchdog integration

[jpds]

Which issue does this PR close?

None.

Rationale

I run my services under systemd - this is a simple integration to have the iggy runtime ping systemd per it's sd_notify integration.

This does not have any effect when the systemd unit is not configured as Type=notify and without WatchdogSec=.

Local Execution

Validated in a set of VMs with the NixOS integration testing framework:

vm-test-run-iggy> server # [   13.822570] iggy-server[937]: 2026-05-11T15:31:32.946941Z  INFO shard-0 server::shard::tasks::periodic::systemd_watchdog: Systemd watchdog enabled, pinging every 15s (timeout: 30s).

vm-test-run-iggy> mcp # [   14.012098] iggy-mcp[860]: 2026-05-11T15:31:33.267809Z  INFO iggy_mcp::systemd: Systemd watchdog enabled, pinging every 15s (timeout: 30s).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 51.29%. Comparing base (9b9be19) to head (575b29e).

Additional details and impacted files

@@              Coverage Diff              @@
##             master    #3233       +/-   ##
=============================================
- Coverage     73.82%   51.29%   -22.53%     
  Complexity      943      943               
=============================================
  Files          1190     1188        -2     
  Lines        107832    94126    -13706     
  Branches      84849    71158    -13691     
=============================================
- Hits          79606    48282    -31324     
- Misses        25469    43242    +17773     
+ Partials       2757     2602      -155     

Components	Coverage Δ
Rust Core	44.90% <100.00%> (-29.97%)	⬇️
Java SDK	60.14% <ø> (ø)
C# SDK	69.13% <ø> (-0.31%)	⬇️
Python SDK	81.43% <ø> (ø)
Node SDK	91.44% <ø> (-0.10%)	⬇️
Go SDK	39.80% <ø> (ø)

Files with missing lines	Coverage Δ
core/ai/mcp/src/main.rs	53.53% <ø> (ø)
core/server/src/shard/mod.rs	90.66% <100.00%> (+0.04%)	⬆️
...re/server/src/shard/tasks/oneshot/config_writer.rs	79.51% <ø> (ø)

... and 298 files with indirect coverage changes

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[hubcio]

overall i think it's solid PR, at first I didn't want to create systemd dependency in iggy itself but your feature approach seems reasonable. i have a couple of follow-up items not tied to a specific line in this diff:

• track an issue to port systemd integration to core/server-ng because current core/server will be replaced by it (this is for us, we dont want to forget it before release)
• optional follow-up PR, preferably docs only for https://iggy.apache.org/docs/ (repo https://github.com/apache/iggy-website/ ): iggy-server.service skeleton with Type=notify, recommended WatchdogSec=, and hardening directives (ProtectSystem, PrivateTmp, NoNewPrivileges, CapabilityBoundingSet). i think it would be nice-to-have.

also: will the compilation for macos with feature systemd fail? or is systemd crate portable and uses some macos mechanism?

[jpds]

also: will the compilation for macos with feature systemd fail? or is systemd crate portable and uses some macos mechanism?

sd-notify itself is pure Rust, there's no libsystemd linkage, so --features systemd would compile fine on macOS; and then just no-op at runtime since no notification socket is set.

I've adjusted the code to address the review comments.

optional follow-up PR, preferably docs only for https://iggy.apache.org/docs/ (repo https://github.com/apache/iggy-website/ ): iggy-server.service skeleton with Type=notify, recommended WatchdogSec=, and hardening directives (ProtectSystem, PrivateTmp, NoNewPrivileges, CapabilityBoundingSet)

I already made a systemd unit definition over at NixOS/nixpkgs#519080 (if you want to pinch ideas from it).

[hubcio]

@jpds thanks for contribution. we merged this, but upcoming release will take from 2-3 weeks to 2-3 months, depend on when we finish cluster feature.