Add pool management.

pool.go

@@ -0,0 +1,251 @@
+package gql
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	libpack_logger "github.com/lukaszraczylo/go-simple-graphql/logging"
+)
+
+// warmupConnectionPool pre-creates connections by executing warmup queries
+// This establishes connections in the pool before actual traffic arrives
+func (b *BaseClient) warmupConnectionPool() {
+	b.Logger.Info(&libpack_logger.LogMessage{
+		Message: "Warming up connection pool",
+		Pairs: map[string]interface{}{
+			"pool_size":    b.pool_size,
+			"warmup_query": b.pool_warmup_query,
+			"endpoint":     b.endpoint,
+		},
+	})
+
+	startTime := time.Now()
+	var wg sync.WaitGroup
+	successCount := 0
+	failCount := 0
+	var mu sync.Mutex
+
+	// Pre-create connections concurrently
+	for i := 0; i < b.pool_size; i++ {
+		wg.Add(1)
+		go func(index int) {
+			defer wg.Done()
+
+			// Execute warmup query to establish connection
+			_, err := b.Query(b.pool_warmup_query, nil, nil)
+
+			mu.Lock()
+			if err != nil {
+				failCount++
+				b.Logger.Warning(&libpack_logger.LogMessage{
+					Message: "Failed to warm up connection",
+					Pairs: map[string]interface{}{
+						"connection_index": index,
+						"error":            err.Error(),
+					},
+				})
+			} else {
+				successCount++
+				b.Logger.Debug(&libpack_logger.LogMessage{
+					Message: "Connection warmed up successfully",
+					Pairs: map[string]interface{}{
+						"connection_index": index,
+					},
+				})
+			}
+			mu.Unlock()
+		}(i)
+	}
+
+	wg.Wait()
+	duration := time.Since(startTime)
+
+	b.Logger.Info(&libpack_logger.LogMessage{
+		Message: "Connection pool warmup completed",
+		Pairs: map[string]interface{}{
+			"successful":  successCount,
+			"failed":      failCount,
+			"total":       b.pool_size,
+			"duration_ms": duration.Milliseconds(),
+		},
+	})
+}
+
+// startPoolHealthMonitor starts a background goroutine that periodically
+// checks and maintains pool health by sending health check queries
+func (b *BaseClient) startPoolHealthMonitor() {
+	b.Logger.Info(&libpack_logger.LogMessage{
+		Message: "Starting connection pool health monitor",
+		Pairs: map[string]interface{}{
+			"check_interval": b.pool_health_interval,
+			"pool_size":      b.pool_size,
+		},
+	})
+
+	go func() {
+		ticker := time.NewTicker(b.pool_health_interval)
+		defer ticker.Stop()
+
+		for {
+			select {
+			case <-ticker.C:
+				b.performPoolHealthCheck()
+			case <-b.pool_stop:
+				b.Logger.Info(&libpack_logger.LogMessage{
+					Message: "Stopping connection pool health monitor",
+					Pairs:   nil,
+				})
+				return
+			}
+		}
+	}()
+}
+
+// performPoolHealthCheck executes health check queries to maintain pool connections
+// This keeps connections alive and detects/replaces dead connections
+func (b *BaseClient) performPoolHealthCheck() {
+	b.Logger.Debug(&libpack_logger.LogMessage{
+		Message: "Performing pool health check",
+		Pairs: map[string]interface{}{
+			"pool_size": b.pool_size,
+		},
+	})
+
+	startTime := time.Now()
+	var wg sync.WaitGroup
+	healthyCount := 0
+	unhealthyCount := 0
+	var mu sync.Mutex
+
+	// Check a subset of connections to ensure pool health
+	// We check pool_size/2 to balance between thoroughness and overhead
+	checkCount := max(1, b.pool_size/2)
+
+	for i := 0; i < checkCount; i++ {
+		wg.Add(1)
+		go func(index int) {
+			defer wg.Done()
+
+			// Create a context with timeout for health check
+			ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+			defer cancel()
+
+			// Use a channel to handle timeout
+			done := make(chan error, 1)
+			go func() {
+				_, err := b.Query(b.pool_warmup_query, nil, nil)
+				done <- err
+			}()
+
+			select {
+			case err := <-done:
+				mu.Lock()
+				if err != nil {
+					unhealthyCount++
+					b.Logger.Warning(&libpack_logger.LogMessage{
+						Message: "Pool health check failed",
+						Pairs: map[string]interface{}{
+							"check_index": index,
+							"error":       err.Error(),
+						},
+					})
+				} else {
+					healthyCount++
+				}
+				mu.Unlock()
+			case <-ctx.Done():
+				mu.Lock()
+				unhealthyCount++
+				b.Logger.Warning(&libpack_logger.LogMessage{
+					Message: "Pool health check timeout",
+					Pairs: map[string]interface{}{
+						"check_index": index,
+					},
+				})
+				mu.Unlock()
+			}
+		}(i)
+	}
+
+	wg.Wait()
+	duration := time.Since(startTime)
+
+	b.Logger.Debug(&libpack_logger.LogMessage{
+		Message: "Pool health check completed",
+		Pairs: map[string]interface{}{
+			"healthy":     healthyCount,
+			"unhealthy":   unhealthyCount,
+			"checked":     checkCount,
+			"duration_ms": duration.Milliseconds(),
+		},
+	})
+
+	// If more than 50% of checks failed, trigger a pool refresh
+	if unhealthyCount > checkCount/2 {
+		b.Logger.Warning(&libpack_logger.LogMessage{
+			Message: "Pool health degraded, triggering refresh",
+			Pairs: map[string]interface{}{
+				"unhealthy_ratio": float64(unhealthyCount) / float64(checkCount),
+			},
+		})
+		b.refreshConnectionPool()
+	}
+}
+
+// refreshConnectionPool attempts to refresh the connection pool
+// by executing warmup queries to replace stale connections
+func (b *BaseClient) refreshConnectionPool() {
+	b.Logger.Info(&libpack_logger.LogMessage{
+		Message: "Refreshing connection pool",
+		Pairs: map[string]interface{}{
+			"pool_size": b.pool_size,
+		},
+	})
+
+	var wg sync.WaitGroup
+	refreshCount := max(1, b.pool_size/3) // Refresh 1/3 of pool
+
+	for i := 0; i < refreshCount; i++ {
+		wg.Add(1)
+		go func(index int) {
+			defer wg.Done()
+
+			_, err := b.Query(b.pool_warmup_query, nil, nil)
+			if err != nil {
+				b.Logger.Debug(&libpack_logger.LogMessage{
+					Message: "Pool refresh connection failed",
+					Pairs: map[string]interface{}{
+						"connection_index": index,
+						"error":            err.Error(),
+					},
+				})
+			} else {
+				b.Logger.Debug(&libpack_logger.LogMessage{
+					Message: "Pool connection refreshed",
+					Pairs: map[string]interface{}{
+						"connection_index": index,
+					},
+				})
+			}
+		}(i)
+	}
+
+	wg.Wait()
+}
+
+// StopPoolMonitor gracefully stops the pool health monitor
+// Call this when shutting down the application
+func (b *BaseClient) StopPoolMonitor() {
+	if b.pool_warmup_enabled {
+		b.Logger.Info(&libpack_logger.LogMessage{
+			Message: "Stopping pool monitor",
+			Pairs:   nil,
+		})
+		select {
+		case b.pool_stop <- true:
+		default:
+			// Channel already has a value or monitor already stopped
+		}
+	}
+}