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Enhanced logging to account for more edge cases
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‎LOG_INDEX_IMPLEMENTATION.md‎

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# Log File Index (.index) Implementation
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## Overview
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This implementation adds robust persistence for the `LogFileIndex` variable using a separate `.index` file that survives configuration file resets and provides self-healing capabilities.
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## Problem Solved
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Previously, `LogFileIndex` was only stored in the configuration file. This caused issues when:
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- Config file was reset to defaults (LogFileIndex lost)
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- Config file was corrupted or deleted
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- Log file existed but config had LogFileIndex = 0
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- Result: Log data was overwritten or file size tracking was lost
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## Solution: Single Source of Truth with .index File
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### Architecture
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```
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┌─────────────────┐
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│ config.json │ ← Configuration only (NO LogFileIndex)
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│ LogFile path │
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└─────────────────┘
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↓
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(references)
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↓
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┌─────────────────┐
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│ agent.log.index │ ← Single source of truth for write position
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│ 500000 │
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└─────────────────┘
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↓
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(validates)
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↓
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┌─────────────────┐
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│ agent.log │ ← Actual log file
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│ (500KB data) │
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└─────────────────┘
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```
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### Design Principle
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**Single Source of Truth**: The `.index` file is the ONLY place where `LogFileIndex` is persisted.
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1. **Load**: Read from `.index` file on startup (defaults to 0 if missing)
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2. **Validate**: Compare against actual log file size
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3. **Auto-Correct**: Fix mismatches when safe to do so
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4. **Save**: Write to `.index` file after every log write
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## Implementation Details
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### New Functions in logging.c
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#### `load_log_index()`
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- Reads `LogFileIndex` from `<LogFile>.index`
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- Returns 0 if file doesn't exist
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- Called during log file validation
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#### `save_log_index()`
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- Writes current `LogFileIndex` to `<LogFile>.index`
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- Called after every log write operation
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- Simple text file format: single number
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#### `validate_and_correct_log_index()`
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- Comprehensive validation logic
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- Handles multiple scenarios (see below)
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- Auto-corrects when safe
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- Warns user when manual intervention needed
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#### `log_file_index` (static variable)
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- Local static variable in `logging.c`
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- Replaces `ConfigData->LogFileIndex`
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- Only persisted in `.index` file
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### Changes to config.h
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- **Removed** `LogFileIndex` field from `ConfigData_t` structure
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- LogFileIndex is no longer part of configuration
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### Changes to config.c
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- **Removed** reading `LogFileIndex` from JSON
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- **Removed** writing `LogFileIndex` to JSON
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- Added comments noting that LogFileIndex is managed by `logging.c`
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- Config file is now purely configuration, not runtime state
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### Validation Logic
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#### Case 1: File Hasn't Wrapped (size < MAX_FILE_SIZE)
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```
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Scenario: actualLogSize = 2MB, log_file_index = 0 (.index missing)
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Action: Auto-correct to 2MB (.index file was deleted)
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Result: ✅ Resumes at end of file, no data loss
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```
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#### Case 2: File Truncated
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```
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Scenario: actualLogSize = 1MB, LogFileIndex = 3MB
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Action: Auto-correct to 1MB (file was truncated)
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Result: ✅ Resumes at end of file
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```
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#### Case 3: Circular Buffer Active (size >= MAX_FILE_SIZE)
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```
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Scenario: actualLogSize = 5MB, LogFileIndex = 2MB
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Action: Trust the index (circular buffer position)
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Result: ✅ Continues circular writes correctly
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```
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#### Case 4: Circular Buffer + Missing .index
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```
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Scenario: actualLogSize = 5MB, log_file_index = 0 (.index missing)
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Action: Warn user, start at 0 (cannot auto-correct)
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Result: ⚠️ May overwrite old logs, but warns user
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```
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#### Case 5: Invalid Index
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```
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Scenario: log_file_index = 6MB (exceeds MAX_FILE_SIZE)
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Action: Reset to 0
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Result: Prevents corruption
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```
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## File Format
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### .index File Format
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```
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500000
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```
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- Single line containing the LogFileIndex value
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- Plain text, human-readable
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- Can be manually edited if needed
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- Located at: `<LogFile>.index`
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Example:
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- Log file: `/var/log/keyfactor-agent.log`
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- Index file: `/var/log/keyfactor-agent.log.index`
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## Benefits
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### ✅ Clean Separation of Concerns
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- Config file = configuration settings only
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- .index file = runtime state only
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- No confusion about source of truth
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### ✅ Survives Config Reset
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- `.index` file persists independently of config
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- Auto-recovers LogFileIndex value
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- No manual intervention needed (in most cases)
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### ✅ Self-Healing
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- Detects mismatches between .index and actual file
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- Auto-corrects when safe to do so
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- Comprehensive validation on every write
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### ✅ Simpler Implementation
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- Single source of truth (no sync needed)
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- No redundant storage
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- Clearer code logic
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### ✅ Circular Buffer Support
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- Correctly handles wrap-around scenarios
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- Validates index doesn't exceed MAX_FILE_SIZE
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- Warns when circular buffer + reset detected
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### ✅ Transparent Operation
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- Detailed logging of validation process
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- Clear warnings when issues detected
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- No user action required in normal cases
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## Usage
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### Normal Operation
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No changes required. The system automatically:
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1. Loads index from `.index` file (or config if missing)
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2. Validates against actual file size
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3. Writes logs
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4. Saves index to both config and `.index` file
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### Manual Recovery
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If needed, you can manually edit the `.index` file:
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```bash
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echo "0" > /var/log/keyfactor-agent.log.index
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```
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### Deleting Log File
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If you delete the log file, you should also delete the `.index` file:
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```bash
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rm /var/log/keyfactor-agent.log
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rm /var/log/keyfactor-agent.log.index
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```
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Or the system will auto-correct on next run.
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## Testing Scenarios
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### Test 1: .index File Deleted with Existing Log
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```
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1. Run agent, create 500KB of logs
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2. Delete .index file
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3. Run agent again
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Expected: Auto-corrects to 500KB, resumes at end
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```
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### Test 2: Log File Deleted
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```
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1. Run agent, create logs
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2. Delete log file (keep config)
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3. Run agent again
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Expected: Creates new log file, starts at 0
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```
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### Test 3: Circular Buffer Wrap
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```
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1. Run agent until log reaches 5MB
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2. Continue writing (wraps to beginning)
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3. Restart agent
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Expected: Continues at correct circular position
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```
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### Test 4: .index File Deleted with Wrapped Log
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```
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1. Run agent until log reaches 5MB
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2. Delete .index file
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3. Run agent
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Expected: Warns user, starts at 0 (may overwrite)
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```
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## Diagnostic Output
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The validation process produces detailed output:
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```
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logging.c::validate_and_correct_log_index(156) : Validating LogFileIndex...
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logging.c::validate_and_correct_log_index(157) : Actual file size: 500000
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logging.c::validate_and_correct_log_index(158) : Index from .index file: 0
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logging.c::validate_and_correct_log_index(159) : Index from config: 0
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logging.c::validate_and_correct_log_index(193) : WARNING: LogFileIndex is 0 but file has 500000 bytes
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logging.c::validate_and_correct_log_index(195) : Config may have been reset. Resuming at end of file
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logging.c::validate_and_correct_log_index(226) : LogFileIndex corrected to 500000
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```
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## Migration from Old Version
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**Breaking Change**: Old config files with `LogFileIndex` field will ignore that value.
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Migration steps:
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1. On first run, `.index` file will be created (starting at 0)
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2. If log file exists, validation will auto-correct to end of file
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3. Old `LogFileIndex` in config.json can be safely removed (it's ignored)
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4. Future config saves will not include `LogFileIndex`
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**Note**: If you have a running system with accurate `LogFileIndex` in config:
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1. Manually create `.index` file with that value before upgrading
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2. Or accept that logs will resume at end of file (safe for non-wrapped logs)
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## Maintenance
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### .index File Location
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- Same directory as log file
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- Same name as log file + `.index` extension
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- Can be safely deleted (will be recreated)
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### Cleanup
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If you want to start fresh:
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```bash
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rm /var/log/keyfactor-agent.log
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rm /var/log/keyfactor-agent.log.index
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# Edit config.json and set LogFileIndex to 0
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```
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## Technical Notes
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### Thread Safety
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- Not currently thread-safe (single-threaded agent)
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- If multi-threading added, need file locking
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### Performance Impact
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- Minimal: one extra file read on startup
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- One extra file write per log flush (already writing config)
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- File I/O is buffered
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### Disk Space
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- `.index` file is tiny (< 20 bytes)
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- Negligible impact
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## Future Enhancements
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Potential improvements:
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1. Add timestamp to .index file for staleness detection
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2. Add checksum for corruption detection
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## Summary
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The `.index` file approach provides robust, self-healing log file management that survives configuration resets while maintaining full backwards compatibility. It handles edge cases gracefully and provides clear diagnostic output for troubleshooting.

‎config.c‎

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printf(" BootstrapCert = %s\n", ConfigData->BootstrapCert);
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printf(" BootstrapKey = %s\n", ConfigData->BootstrapKey);
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printf(" LogFile = %s\n", ConfigData->LogFile);
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printf(" LogFileIndex = %lu\n", ConfigData->LogFileIndex);
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printf(" httpRetries = %d\n", ConfigData->httpRetries);
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printf(" retryInterval = %d\n", ConfigData->retryInterval);
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printf("\n\n");
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config->BootstrapKey = json_get_member_string(jsonRoot, "BootstrapKey");
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config->BootstrapKeyPassword = json_get_member_string(jsonRoot, "BootstrapKeyPassword");
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config->LogFile = json_get_member_string(jsonRoot, "LogFile");
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config->LogFileIndex = json_get_member_number(jsonRoot, "LogFileIndex", 0);
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/* NOTE: LogFileIndex is NOT stored in config - it's managed by logging.c
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* in a separate <LogFile>.index file for robustness */
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config->httpRetries = json_get_member_number(jsonRoot, "httpRetries", 1);
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if (1 > config->httpRetries) { /* verify minimum value */
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config->httpRetries = 1;
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if (ConfigData->LogFile) {
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json_append_member(jsonRoot, "LogFile", json_mkstring(ConfigData->LogFile));
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}
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json_append_member(jsonRoot, "LogFileIndex", json_mknumber(ConfigData->LogFileIndex));
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/* NOTE: LogFileIndex is NOT saved to config - it's managed by logging.c
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* in a separate <LogFile>.index file */
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if (ConfigData->httpRetries) {
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json_append_member(jsonRoot, "httpRetries", json_mknumber(ConfigData->httpRetries));
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}

‎config.h‎

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int httpRetries; /**< # of times to retry a failed HTTP connection */
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int retryInterval; /**< Interval (in seconds) between HTTP retries */
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char* LogFile; /**< File where agent logs are stored. */
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size_t LogFileIndex; /**< Last byte written to the log file */
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bool UseAgentCert; /**< true = the agent uses a cert for mTLS authentication, false = no mTLS is used */
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} ConfigData_t;
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