Added wal-g exporter to prometheus

exporter/.golangci.yml

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+run:
+  timeout: 5m
+  modules-download-mode: readonly
+
+linters:
+  enable:
+    - gofmt
+    - goimports
+    - govet
+    - ineffassign
+    - misspell
+    - revive
+    - staticcheck
+    - unused
+  disable:
+    - errcheck
+    - gosec
+    - gosimple
+
+linters-settings:
+  revive:
+    rules:
+      - name: unused-parameter
+        disabled: true
+      - name: exported
+        disabled: true
+
+issues:
+  exclude-use-default: false
+  max-issues-per-linter: 0
+  max-same-issues: 0
+
+  exclude-rules:
+    - text: "should have comment"
+      linters:
+        - revive
+    - text: "comment on exported"
+      linters:
+        - revive 

exporter/README.md

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+# WAL-G Prometheus Exporter
+
+A Prometheus exporter for WAL-G backup and WAL metrics for PostgreSQL databases.
+
+## Features
+
+- **Backup lag monitoring**: Track time since last backup-push (full and delta backups)
+- **WAL lag monitoring**: Monitor time since last wal-push operation
+- **LSN delta lag**: Calculate LSN lag in bytes between current and archived WAL
+- **PITR window**: Monitor point-in-time recovery window size
+- **Error monitoring**: Track WAL-G operation errors
+- **WAL integrity**: Monitor WAL segment integrity status per timeline
+
+## Metrics
+
+The exporter provides the following metrics:
+
+### Backup Metrics
+- `walg_backup_lag_seconds{backup_type}` - Time since last backup-push in seconds
+- `walg_backup_count{backup_type}` - Number of backups (full/delta)
+- `walg_backup_timestamp{backup_type}` - Timestamp of last backup
+
+### WAL Metrics
+- `walg_wal_lag_seconds{timeline}` - Time since last wal-push in seconds
+- `walg_lsn_lag_bytes{timeline}` - LSN delta lag in bytes
+- `walg_wal_integrity_status{timeline}` - WAL integrity status (1 = OK, 0 = ERROR)
+
+### PITR Metrics
+- `walg_pitr_window_seconds` - Point-in-time recovery window size in seconds
+
+### Error Metrics
+- `walg_errors_total{operation,error_type}` - Total number of WAL-G errors
+
+### Exporter Metrics
+- `walg_scrape_duration_seconds` - Duration of the last scrape
+- `walg_scrape_errors_total` - Total number of scrape errors
+
+## Installation
+
+### From Source
+
+```bash
+cd exporter
+go build -o walg-exporter .
+```
+
+### Using Docker
+
+```bash
+docker build -t walg-exporter .
+docker run -p 9351:9351 walg-exporter
+```
+
+## Usage
+
+### Command Line Options
+
+```bash
+./walg-exporter [flags]
+```
+
+**Flags:**
+- `--web.listen-address` - Address to listen on (default: `:9351`)
+- `--web.telemetry-path` - Path for metrics endpoint (default: `/metrics`)
+- `--walg.path` - Path to wal-g binary (default: `wal-g`)
+- `--scrape.interval` - Scrape interval (default: `60s`)
+- `--log.level` - Log level (default: `info`)
+
+### Example
+
+```bash
+# Basic usage
+./walg-exporter
+
+# Custom configuration
+./walg-exporter \
+  --web.listen-address=":8080" \
+  --walg.path="/usr/local/bin/wal-g" \
+  --scrape.interval="30s"
+```
+
+## Configuration
+
+The exporter requires WAL-G to be properly configured and accessible. Ensure that:
+
+1. WAL-G is installed and in PATH (or specify with `--walg.path`)
+2. WAL-G configuration is properly set up (environment variables, config file)
+3. The exporter has access to execute WAL-G commands
+
+### WAL-G Commands Used
+
+The exporter executes the following WAL-G commands:
+- `wal-g backup-list --detail --json` - Get backup information
+- `wal-g wal-show --detailed-json` - Get WAL segment information
+
+## Prometheus Configuration
+
+Add the following to your Prometheus configuration:
+
+```yaml
+scrape_configs:
+  - job_name: 'walg-exporter'
+    static_configs:
+      - targets: ['localhost:9351']
+    scrape_interval: 60s
+    metrics_path: /metrics
+```
+
+## Grafana Dashboard
+
+Example Grafana queries:
+
+### Backup Lag
+```promql
+walg_backup_lag_seconds{backup_type="full"}
+```
+
+### WAL Lag
+```promql
+walg_wal_lag_seconds
+```
+
+### PITR Window (in hours)
+```promql
+walg_pitr_window_seconds / 3600
+```
+
+### Error Rate
+```promql
+rate(walg_errors_total[5m])
+```
+
+## Development
+
+### Running Tests
+
+```bash
+go test -v ./...
+```
+
+### Running Benchmarks
+
+```bash
+go test -bench=. -benchmem ./...
+```
+
+### Mock Testing
+
+The exporter includes comprehensive tests with mock WAL-G commands:
+
+```bash
+# Create a mock wal-g script
+cat > mock-wal-g << 'EOF'
+#!/bin/bash
+case "$1" in
+  "backup-list")
+    echo '[{"backup_name":"test","time":"2024-01-01T12:00:00Z","is_full":true}]'
+    ;;
+  "wal-show")
+    echo '{"integrity":{"status":"OK","details":[{"timeline_id":1,"status":"FOUND"}]}}'
+    ;;
+esac
+EOF
+chmod +x mock-wal-g
+
+# Test with mock
+./walg-exporter --walg.path=./mock-wal-g
+```
+
+## Architecture
+
+The exporter consists of several components:
+
+- **main.go**: HTTP server and command-line interface
+- **exporter.go**: Core Prometheus collector implementation
+- **wal_lag.go**: LSN parsing and WAL lag calculation
+- **pitr.go**: PITR window calculation logic
+
+### LSN Parsing
+
+The exporter includes a full LSN parser that handles PostgreSQL LSN format:
+
+```go
+lsn, err := ParseLSN("0/1A2B3C4D")
+fmt.Println(lsn.String()) // "0/1A2B3C4D"
+fmt.Println(lsn.Bytes())  // 439041101
+```
+
+### Lag Calculation
+
+WAL and LSN lag calculations:
+
+```go
+// Time-based lag
+walLag := calculateWalLag(lastWalTime)
+
+// LSN-based lag in bytes
+lsnLag := calculateLSNLag(currentLSN, lastArchivedLSN)
+```
+
+## Troubleshooting
+
+### Common Issues
+
+1. **WAL-G command not found**
+   - Ensure WAL-G is in PATH or specify with `--walg.path`
+   - Check that WAL-G is executable
+
+2. **Permission denied**
+   - Ensure the exporter has permission to execute WAL-G
+   - Check WAL-G configuration file permissions
+
+3. **No metrics**
+   - Verify WAL-G commands work manually
+   - Check exporter logs for errors
+   - Ensure WAL-G is properly configured
+
+### Debug Mode
+
+Enable debug logging:
+
+```bash
+./walg-exporter --log.level=debug
+```
+
+### Health Check
+
+The exporter provides a health endpoint:
+
+```bash
+curl http://localhost:9351/
+```
+
+## Contributing
+
+1. Fork the repository
+2. Create a feature branch
+3. Add tests for new functionality
+4. Ensure all tests pass
+5. Submit a pull request
+
+## License
+
+This project is licensed under the same license as WAL-G.
+
+## Support
+
+For issues and questions:
+- Check the [WAL-G documentation](https://github.com/wal-g/wal-g)
+- File an issue in the WAL-G repository
+- Join the WAL-G community discussions