fix(agentex): build valid OTLP metrics URLs (#346)

## 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_comment -->

<h3>Greptile Summary</h3>

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`.

<details><summary><h3>Confidence Score: 5/5</h3></summary>

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.
</details>

<details><summary><h3>Important Files Changed</h3></summary>

| 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. |

</details>

<details><summary><h3>Flowchart</h3></summary>

<a href="#gh-light-mode-only">

```mermaid
%%{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
```

</a>
<a href="#gh-dark-mode-only">

```mermaid
%%{init: {'theme': 'base', 'themeVariables': {"darkMode": true, "background": "#0d1117", "primaryColor": "#21262d", "primaryTextColor": "#e6edf3", "primaryBorderColor": "#8b949e", "lineColor": "#8b949e", "textColor": "#e6edf3", "edgeLabelBackground": "#161b22", "actorBkg": "#21262d", "actorBorder": "#8b949e", "actorTextColor": "#e6edf3", "actorLineColor": "#8b949e", "signalColor": "#8b949e", "signalTextColor": "#e6edf3", "noteBkgColor": "#373320", "noteBorderColor": "#d4a72c", "noteTextColor": "#f0e6c0", "labelBoxBkgColor": "#21262d", "labelBoxBorderColor": "#8b949e", "labelTextColor": "#e6edf3", "loopTextColor": "#e6edf3", "activationBkgColor": "#30363d", "activationBorderColor": "#8b949e"}}}%%
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
```

</a>
</details>

<sub>Reviews (2): Last reviewed commit: ["fix(agentex): default empty
OTLP
metrics..."](24de57e)
| [Re-trigger
Greptile](https://app.greptile.com/api/retrigger?id=42166768)</sub>

<!-- /greptile_comment -->

Author: scale-sf

agentex/src/temporal/run_worker.py

@@ -48,6 +48,31 @@
 
 # Task queue name for agentex server operations
 AGENTEX_SERVER_TASK_QUEUE = "agentex-server"
+OTLP_METRICS_DEFAULT_PORT = 4317
+
+
+def build_metrics_url(host_url: str | None) -> str | None:
+    """Build the worker OTLP metrics URL from DD_AGENT_HOST."""
+    if not host_url:
+        return None
+
+    host = host_url.strip()
+    if not host:
+        return None
+
+    port: str | int = OTLP_METRICS_DEFAULT_PORT
+    if host.startswith("["):
+        bracket_end = host.find("]")
+        if bracket_end != -1:
+            rest = host[bracket_end + 1 :]
+            port = rest[1:] or port if rest.startswith(":") else port
+            host = host[1:bracket_end]
+    elif host.count(":") == 1:
+        host, port = host.split(":", 1)
+
+    if ":" in host:
+        host = f"[{host}]"
+    return f"http://{host}:{port}"
 
 # Global worker instance
 health_check_worker: Worker | None = None
@@ -93,7 +118,7 @@ async def run_worker(
 
         # Check for metrics configuration
         host_url = os.environ.get("DD_AGENT_HOST")
-        metrics_url = f"http://[{host_url}]:4317" if host_url else None
+        metrics_url = build_metrics_url(host_url)
         if metrics_url:
             logger.info(f"Configuring worker with metrics URL: {metrics_url}")
 

agentex/tests/unit/temporal/test_run_worker_metrics_url.py

@@ -0,0 +1,42 @@
+import pytest
+from src.temporal.run_worker import build_metrics_url
+
+
+@pytest.mark.unit
+def test_metrics_url_is_none_without_host():
+    assert build_metrics_url(None) is None
+    assert build_metrics_url("") is None
+    assert build_metrics_url("   ") is None
+
+
+@pytest.mark.unit
+@pytest.mark.parametrize("host", ["localhost", "datadog-agent", "10.0.0.5"])
+def test_hostname_and_ipv4_hosts_are_not_bracketed(host):
+    assert build_metrics_url(host) == f"http://{host}:4317"
+
+
+@pytest.mark.unit
+@pytest.mark.parametrize(
+    ("host", "expected"),
+    [
+        ("::1", "http://[::1]:4317"),
+        ("fe80::1", "http://[fe80::1]:4317"),
+        ("[::1]", "http://[::1]:4317"),
+        ("[::1]:", "http://[::1]:4317"),
+    ],
+)
+def test_ipv6_literals_are_bracketed(host, expected):
+    assert build_metrics_url(host) == expected
+
+
+@pytest.mark.unit
+@pytest.mark.parametrize(
+    ("host", "expected"),
+    [
+        ("datadog-agent:5555", "http://datadog-agent:5555"),
+        ("10.0.0.5:5555", "http://10.0.0.5:5555"),
+        ("[::1]:5555", "http://[::1]:5555"),
+    ],
+)
+def test_explicit_port_is_preserved(host, expected):
+    assert build_metrics_url(host) == expected