SEC-1601: JMX exporter

[Alexander-Cairns]

Summary by CodeRabbit

Release Notes

• New Features

  • Integrated JMX exporter with configurable rules to enable Java Management Extensions metrics collection and monitoring capabilities within the application runtime environment.

• Chores

  • Updated Java memory environment configuration with improved variable naming and structure. Introduced a dedicated startup entrypoint script that manages the application initialization process.

[coderabbitai]

Walkthrough

The Docker configuration is modified to introduce JMX exporter integration for monitoring and replace the heap-specific ALPACA_HEAP environment variable with a generalized JAVA_MEMORY variable. A new entrypoint script is created to encapsulate startup logic and enable the Java agent.

Changes

Cohort / File(s)	Summary
Docker build configuration Dockerfile	Replaces ALPACA_HEAP with JAVA_MEMORY env variable; adds JMX_EXPORTER_VERSION and JMX_EXPORTER_DIGEST build arguments; downloads and integrates JMX Prometheus Java agent; creates /entrypoint.sh via heredoc-based COPY; changes CMD to invoke the new entrypoint script instead of direct Java execution.
JMX configuration jmx.yml	New configuration file for JMX exporter with a rules block containing a pattern-matching rule (.*).

Sequence Diagram

sequenceDiagram
    participant Docker as Docker Container
    participant Entrypoint as /entrypoint.sh
    participant JVM as Java Virtual Machine
    participant App as Alpaca App
    participant JMX as JMX Exporter Agent

    Docker->>Entrypoint: CMD executes entrypoint.sh
    Entrypoint->>Entrypoint: Set JAVA_OPTS with -Xmx${JAVA_MEMORY}
    Entrypoint->>Entrypoint: Enable JMX agent via javaagent flag
    Entrypoint->>JVM: Launch java with agent + memory config
    JVM->>JMX: Initialize JMX Prometheus agent
    JVM->>App: Start Alpaca application
    JMX-->>JVM: Monitor & export metrics
    App-->>Docker: Application running

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Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

• Verify JMX exporter version and digest are correctly specified and match upstream releases
• Confirm the entrypoint script logic (variable substitution, Java agent syntax) is correct
• Check that the jmx.yml rules configuration is appropriate for the monitoring use case

Poem

🐰 A Java agent hops into town,
With JMX metrics to track and renown,
The entrypoint script now leads the way,
Memory management refined today,
Alpaca runs faster, monitored with care! 📊

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'SEC-1601: JMX exporter' accurately reflects the main change: integrating JMX exporter functionality into the Docker image with associated configuration and entrypoint modifications.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch SEC-1601

Warning

Review ran into problems

🔥 Problems

Errors were encountered while retrieving linked issues.

Errors (1)

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[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (3)

Dockerfile (3)

38-54: Consider the implications of set -x verbose logging and JMX port configurability.

The entrypoint script uses set -x (line 41) which enables verbose output of all commands before execution. While useful for debugging, this will produce logs for every environment variable substitution and command execution in production, potentially cluttering logs.

Additionally, the JMX agent port (3001 on line 51) is hardcoded with no mechanism to override it via environment variable. Consider:

• Whether set -x is appropriate for production logging, or if it should be conditional
• Making the JMX port configurable (e.g., JMX_EXPORTER_PORT ENV var with default 3001)

---

23-54: Document JMX exporter security and operational configuration.

The JMX exporter is now integrated and listening on port 3001 with configuration from jmx.yml. A few operational and security considerations:

• No TLS/Authentication: JMX exporter listens unencrypted; ensure the port is properly firewalled and not exposed to untrusted networks
• Port Binding: The agent binds to all interfaces by default; document the port exposure strategy
• Metrics Scope: Combined with the broad ".*" pattern in jmx.yml, all available metrics will be exposed—ensure this aligns with your security and privacy requirements

Please document:

• How the JMX metrics port should be secured/firewalled in deployment
• Which metrics are expected to be exported and whether this is comprehensive or should be narrowed

---

38-54: Add inline documentation to the entrypoint script.

The entrypoint script encapsulates important configuration logic but lacks comments explaining the setup. Consider adding a comment block at the top of the script documenting:

• The purpose of the JMX agent configuration
• How to modify the JMX port if needed
• The significance of set -x for logging

This will help future maintainers understand the startup flow and troubleshoot issues.

📜 Review details

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Review profile: CHILL

Plan: Pro

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📥 Commits

Reviewing files that changed from the base of the PR and between 7adeb68 and 7d2d6f7.

📒 Files selected for processing (2)

• Dockerfile (2 hunks)
• jmx.yml (1 hunks)

🔇 Additional comments (4)

jmx.yml (1)

1-2: Clarify the intent of the overly broad ".*" pattern.

The pattern ".*" matches any string without restrictions. Depending on the jmx_exporter rule semantics, this could expose all available JMX metrics, including potentially sensitive internal attributes.

Please clarify:

• Is this intentionally capturing all metrics for comprehensive monitoring?
• Should the pattern be more restrictive to limit exported metrics to relevant ones?
• Are there any sensitive metrics that should be excluded?

Dockerfile (3)

6-6: Verify shell expansion safety of JAVA_MEMORY variable.

Line 6 defines JAVA_MEMORY="-Xms512m -Xmx512m" which is used unquoted in the entrypoint script (line 50: $JAVA_MEMORY). This relies on shell word-splitting to separate the memory arguments, which works for the default value but creates a risk if users set JAVA_MEMORY with unexpected content (special characters, spaces in values, etc.).

Consider documenting the expected format of JAVA_MEMORY or protecting the expansion with quotes/arrays if stricter validation is needed. For now, please verify this expansion behaves as intended across expected use cases.

Also applies to: 50-50

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23-32: Verify JMX exporter version and checksum validity.

The JMX exporter version 1.4.0 and its associated SHA256 checksum are hardcoded. Please verify:

• Version 1.4.0 is still maintained and has no known security advisories
• The provided checksum matches the official release for this version
• This version is compatible with the Java 11 runtime in use

---

38-56: Verify /entrypoint.sh execution permissions and WORKDIR state.

The entrypoint script is created with --chmod=755 (line 38), making it executable. The WORKDIR is changed to /jmx for JMX setup (line 26) but restored to /opt/alpaca (line 36) before running the application, which is correct.

Please verify:

• The script has proper shebang and bash is available in the image
• The WORKDIR management doesn't cause any unintended side effects