[integration] Added Haystack integration

[lucifertrj]

What & why

This PR adds support to the Haystack Framework- Deepset integration with the OPIK connector. Issue: #44

Trace Screenshot

Checklist

• Linked to its tracking issue (commented to claim it before starting)
• Example is in the right bucket (integrations / guides / use-cases / scripts)
• Folder name is lowercase_with_underscores
• README.md has all required sections; index tables updated if examples were added/renamed/removed
• Dry-run works with no credentials — bash run.sh exits cleanly (this is what CI's secrets-free job runs)
• uv run ruff check . and uv run ruff format --check . are clean
• No credentials or .env files committed
• Dependencies declared in pyproject.toml (uv project); no requirements.txt, no committed uv.lock
• run.sh exists and starts with set -e
• OPIK_PROJECT_NAME is set — exported in run.sh (scripts) or defined in config.py (use-cases/guides)

[LeoRoccoBreedt]

Thanks @lucifertrj — this one's in great shape. I checked out the branch and ran the CI-equivalent checks locally:

• bash run.sh with no creds → exits 0 with meaningful DRY_RUN output
• uv run ruff check . / ruff format --check → clean
• uv sync + dry-run imports everything (incl. SerperDevWebSearch), so haystack-ai / serperdev-haystack / opik>=2.2.0 are all correctly declared
• Tracing genuinely works — I confirmed OpikConnector(name=...) registers OpikTracer as Haystack's global tracer on construction (is_tracing_enabled → True on opik 2.2.13), which is why your trace screenshot is real

Nice work updating the integrations/README.md index and using the nested framework/example layout. Just two things to tidy before we merge, plus a couple of nits.

Should-fix

1. Give the load-bearing OpikConnector(...) line a # WHY: comment.

OpikConnector(name="haystack-multi-agent-scout", project_name=config.OPIK_PROJECT_NAME)

This is the single most important line in the example — its constructor swaps in the global OpikTracer, which is what makes tracing happen — but because the instance is constructed and discarded, it reads like a mistake to anyone copying the code. The repo's code-style rule calls for a # WHY: exactly when a behaviour would surprise a reader, and a dangling constructor qualifies:

# WHY: constructing OpikConnector registers Opik as Haystack's global tracer for the whole
# process; the instance is intentionally unused because we run Agents directly, not via a Pipeline.
OpikConnector(name="haystack-multi-agent-scout", project_name=config.OPIK_PROJECT_NAME)

(Your example README explains this in prose already — this is just so the code itself does too.) Minor bonus: it's created inside build_coordinator, so calling run_agent twice would re-register the tracer each time — harmless, but hoisting it to module init would read cleaner.

2. OPIK_PROJECT_NAME default is inconsistent across files.

• .env.example → haystack-multi-agent
• config.py / run.sh / OpikConnector / README → haystack-multi-agent-scout

Someone who copies .env.example lands in a different project than the docs describe. Align them (suggest standardizing on haystack-multi-agent-scout).

Nits

• Heads-up on CI: this example needs OPENAI_API_KEY and SERPERDEV_API_KEY, and it's hardwired to Haystack's OpenAIChatGenerator (so the cheap-model routing via OPIK_EXAMPLES_MODEL doesn't apply — correctly, since that var is provider-prefixed for litellm). Net effect: the live-run job won't exercise this unless CI has a SerperDev key, so a maintainer may need to run it manually. Not a blocker — inherent to a SerperDev-based example.
• OpikConnector(name="haystack-multi-agent-scout") reuses the project-name string as the connector name; the name is really the trace/connector label, so a distinct descriptive name would be a touch clearer. Trivial.
• .env.example is missing a trailing newline.

Otherwise this is approvable once 1 and 2 are in. Thanks for a clean, well-structured integration!

[lucifertrj]

perfect. I missed the .env.example part for the project name. I will make the fix.

[lucifertrj]

resolved:

• Why comment for constructing OPIKConnector
• Trailing newline in .env.example and keeping the OPIK_PROJECT_NAME as haystack-multi-agent-scout consistent across config.py, run.sh, .env.example, and readme.

@LeoRoccoBreedt