Fix hostname parsing and improve decommission process

[WalBeh]

Summary of changes

Added

• Persistent Logging: Dual logging to both STDOUT and persistent file with automatic rotation

  • New --log-file CLI flag (default: /resource/heapdump/dc_util.log)
  • Automatic file rotation when approaching 1MB to prevent disk space issues
  • Failsafe design - continues STDOUT logging even if file logging fails
  • Essential for debugging Kubernetes lifecycle hooks where container logs may not be accessible
  • Creates directory structure if it doesn't exist

• PostStart Hook Detection: Intelligent detection of StatefulSet PostStart hooks

  • Automatically scans StatefulSet containers for PostStart hooks with dc_util --reset-routing
  • Prevents routing allocation changes when no PostStart hook exists to reset them
  • Solves historical issue where NEW_PRIMARIES routing allocation could not be reliably reset
  • Supports both single dash (-reset-routing) and double dash (--reset-routing) flag formats
  • Precise word boundary matching prevents false positives from similar flag names
  • Logs clear messages when PostStart hooks are found or missing

• Single Node Cluster Detection: Automatic detection and handling of single node clusters

  • Detects when StatefulSet has exactly 1 replica and skips decommission
  • Prevents unnecessary overhead and potential failures in single node deployments
  • Clear logging explains why decommission was skipped
  • Maintains existing behavior for multi-node clusters (≥2 replicas)

• Configurable Lock File Path: New --lock-file CLI flag

  • Default: /resource/heapdump/dc_util.lock
  • Allows customization for different deployment scenarios
  • All lock file operations now use configurable path

• Enhanced Flag Support: Improved command-line flag handling

  • Both -reset-routing and --reset-routing formats now supported
  • Maintains backward compatibility with existing deployments
  • Better error handling and validation

• Multi-Architecture Support: Automatic CPU architecture detection in hook configurations

  • Hook examples now include automatic detection of x86_64/amd64 and aarch64/arm64 architectures
  • Downloads appropriate binary based on detected architecture (dc_util-linux-amd64 or dc_util-linux-arm64)
  • Eliminates need for separate configuration files for different node architectures
  • Graceful error handling for unsupported architectures

Changed

• Routing Allocation Logic: Enhanced PreStop process with PostStart hook detection

  • Routing allocation changes now only occur when corresponding PostStart hook exists
  • Prevents permanent cluster misconfiguration in deployments without PostStart hooks
  • More intelligent decision making based on actual StatefulSet configuration

• Replica Count Handling: Improved logic for different cluster sizes

  • Zero replicas (scaled down): Skips decommission with clear logging
  • Single replica: Skips decommission to prevent failures
  • Multiple replicas: Proceeds with normal decommission process
  • Better log messages explaining the decision for each scenario

• Function Signatures: Updated internal functions to support configurable paths

  • createLockFile() now accepts lock file path parameter
  • removeLockFile() now accepts lock file path parameter
  • lockFileExists() now accepts lock file path parameter
  • handleResetRouting() now accepts lock file path parameter

Improved

• Logging Experience: Comprehensive logging improvements

  • All log messages now appear in both STDOUT and persistent file
  • Better visibility into hook execution for debugging
  • Historical logs available even after pod restarts
  • Easier troubleshooting and operations monitoring

• Documentation: Extensively updated README.md

  • Added "Recent Updates" section highlighting new features
  • New "Replica Count Logic" section with examples
  • Updated CLI parameter table with new flags
  • Enhanced "PostStart Hook Detection" documentation
  • Added complete "Persistent Logging" section with usage examples
  • Updated sample logs sections to reflect new capabilities
  • All hook configuration examples now include automatic architecture detection
  • Clear separation between basic (preStop only) and complete (both hooks) configurations

• Testing: Comprehensive test coverage for all new features

  • TestHasPostStartHookWithResetRouting: PostStart hook detection with various scenarios
  • TestPostStopRoutingAllocationIntegration: Integration tests for routing allocation logic
  • TestLoggingIntegration: Dual logging functionality verification
  • TestLogRotation: File rotation behavior validation
  • TestSingleNodeClusterBehavior: Single node cluster detection tests
  • TestReplicaCountBehavior: Comprehensive replica count handling tests
  • All existing tests updated to work with new function signatures

Checklist

• [x] Link to issue this PR refers to: https://github.com/crate/cloud/issues/2755
• [x] Relevant changes are reflected in CHANGES.rst
• [x] Added or changed code is covered by tests
• [ ] Documentation has been updated if necessary
• [ ] Changed code does not contain any breaking changes (or this is a major version change)