fix(agentex): build valid OTLP metrics URLs

[scale-sf]

Summary

• fix worker OTLP metrics URL construction for normal DD_AGENT_HOST values like localhost, service names, and IPv4 literals
• keep IPv6 literals bracketed and preserve explicit ports
• add focused unit coverage for metrics URL construction

Closes #313. Supersedes stale external PR #323 with the same underlying fix on a fresh branch.

Tests

• uv run ruff check agentex/src/temporal/run_worker.py agentex/tests/unit/temporal/test_run_worker_metrics_url.py
• uv run --package agentex-backend --group test pytest agentex/tests/unit/temporal/test_run_worker_metrics_url.py -m unit -q
• uv run --package agentex-backend --group test pytest agentex/tests/unit/temporal -m unit -q
• Runtime repro with temporalio 1.23.0: old http://[{DD_AGENT_HOST}]:4317 URLs reject localhost, datadog-agent, and 10.0.0.5 with Invalid OTel URL: invalid IPv6 address; build_metrics_url(...) outputs are accepted by Runtime(telemetry=TelemetryConfig(metrics=OpenTelemetryConfig(url=...))).

Greptile Summary

Fixes the OTLP metrics URL construction for Temporal workers by replacing the broken http://[{DD_AGENT_HOST}]:4317 string interpolation with a dedicated build_metrics_url function that correctly handles all common DD_AGENT_HOST shapes and adds focused unit tests for each case.

• build_metrics_url correctly handles plain hostnames, IPv4 literals, bare IPv6 addresses (brackets them), pre-bracketed IPv6 (including the previously-identified empty-trailing-port edge case "[::1]:", now covered by a test), and explicit ports for all host types.
• One unguarded edge case remains: a malformed input that begins with "[" but has no closing "]" bypasses the inner parsing block and is then double-bracketed by the final colon-presence check, producing an invalid URL like http://[[::1]:4317.

Confidence Score: 5/5

Safe to merge — the fix correctly resolves the invalid IPv6-bracket wrapping for all realistic DD_AGENT_HOST values and is well-covered by the new unit tests.

The core bug (wrapping every host in IPv6 brackets) is definitively fixed and tested across all meaningful host shapes. The one unguarded path — a malformed input that begins with an unclosed bracket — is an unrealistic operator configuration and does not affect production behaviour.

No files require special attention; the logic in run_worker.py is straightforward and the test file covers all realistic cases.

Important Files Changed

Filename	Overview
agentex/src/temporal/run_worker.py	Replaces the broken http://[{DD_AGENT_HOST}]:4317 template with build_metrics_url, correctly handling plain hostnames, IPv4, bare IPv6 (brackets them), pre-bracketed IPv6 (strips and re-brackets), and explicit ports. One edge case remains: a malformed input like "[::1" (missing closing bracket) bypasses the inner block and then gets double-bracketed by the trailing guard, producing an invalid URL.
agentex/tests/unit/temporal/test_run_worker_metrics_url.py	New unit tests covering None/empty input, plain hostnames, IPv4, bare IPv6, pre-bracketed IPv6 (including the previously-reported "[::1]:" empty-port case), and explicit-port variants. No tests for the malformed "[::1" (missing closing bracket) case.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[build_metrics_url] --> B{host_url falsy?}
    B -- Yes --> C[return None]
    B -- No --> D[host = host_url.strip]
    D --> E{host empty?}
    E -- Yes --> C
    E -- No --> F[port = 4317 default]
    F --> G{host starts with bracket?}
    G -- Yes --> H[find closing bracket]
    H --> I{bracket found?}
    I -- Yes --> J[parse rest after bracket]
    J --> K{rest starts with colon?}
    K -- Yes --> L[port = rest after colon or default]
    K -- No --> M[port stays default]
    L --> N[host = inner IPv6 address]
    M --> N
    I -- No --> O[host unchanged with leading bracket - BUG PATH]
    G -- No --> P{exactly one colon in host?}
    P -- Yes --> Q[split host and port]
    P -- No --> R[host unchanged]
    Q --> S{colon in host?}
    N --> S
    O --> S
    R --> S
    S -- Yes --> T[wrap host in brackets]
    S -- No --> U[return http://host:port]
    T --> U

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flowchart TD
    A[build_metrics_url] --> B{host_url falsy?}
    B -- Yes --> C[return None]
    B -- No --> D[host = host_url.strip]
    D --> E{host empty?}
    E -- Yes --> C
    E -- No --> F[port = 4317 default]
    F --> G{host starts with bracket?}
    G -- Yes --> H[find closing bracket]
    H --> I{bracket found?}
    I -- Yes --> J[parse rest after bracket]
    J --> K{rest starts with colon?}
    K -- Yes --> L[port = rest after colon or default]
    K -- No --> M[port stays default]
    L --> N[host = inner IPv6 address]
    M --> N
    I -- No --> O[host unchanged with leading bracket - BUG PATH]
    G -- No --> P{exactly one colon in host?}
    P -- Yes --> Q[split host and port]
    P -- No --> R[host unchanged]
    Q --> S{colon in host?}
    N --> S
    O --> S
    R --> S
    S -- Yes --> T[wrap host in brackets]
    S -- No --> U[return http://host:port]
    T --> U

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_{Reviews (2): Last reviewed commit: "fix(agentex): default empty OTLP metrics..." | Re-trigger Greptile}

[smoreinis]

lgtm