Refactor repository

Fix issues
Improve transaction API
Make hardcoded constants configurable
Make error messages consistent and always add context info

internal/repository/config.go

@@ -0,0 +1,67 @@
+// Copyright (C) NHR@FAU, University Erlangen-Nuremberg.
+// All rights reserved. This file is part of cc-backend.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+package repository
+
+import "time"
+
+// RepositoryConfig holds configuration for repository operations.
+// All fields have sensible defaults, so this configuration is optional.
+type RepositoryConfig struct {
+	// CacheSize is the LRU cache size in bytes for job metadata and energy footprints.
+	// Default: 1MB (1024 * 1024 bytes)
+	CacheSize int
+
+	// MaxOpenConnections is the maximum number of open database connections.
+	// Default: 4
+	MaxOpenConnections int
+
+	// MaxIdleConnections is the maximum number of idle database connections.
+	// Default: 4
+	MaxIdleConnections int
+
+	// ConnectionMaxLifetime is the maximum amount of time a connection may be reused.
+	// Default: 1 hour
+	ConnectionMaxLifetime time.Duration
+
+	// ConnectionMaxIdleTime is the maximum amount of time a connection may be idle.
+	// Default: 1 hour
+	ConnectionMaxIdleTime time.Duration
+
+	// MinRunningJobDuration is the minimum duration in seconds for a job to be
+	// considered in "running jobs" queries. This filters out very short jobs.
+	// Default: 600 seconds (10 minutes)
+	MinRunningJobDuration int
+}
+
+// DefaultConfig returns the default repository configuration.
+// These values are optimized for typical deployments.
+func DefaultConfig() *RepositoryConfig {
+	return &RepositoryConfig{
+		CacheSize:              1 * 1024 * 1024, // 1MB
+		MaxOpenConnections:     4,
+		MaxIdleConnections:     4,
+		ConnectionMaxLifetime:  time.Hour,
+		ConnectionMaxIdleTime:  time.Hour,
+		MinRunningJobDuration:  600, // 10 minutes
+	}
+}
+
+// repoConfig is the package-level configuration instance.
+// It is initialized with defaults and can be overridden via SetConfig.
+var repoConfig *RepositoryConfig = DefaultConfig()
+
+// SetConfig sets the repository configuration.
+// This must be called before any repository initialization (Connect, GetJobRepository, etc.).
+// If not called, default values from DefaultConfig() are used.
+func SetConfig(cfg *RepositoryConfig) {
+	if cfg != nil {
+		repoConfig = cfg
+	}
+}
+
+// GetConfig returns the current repository configuration.
+func GetConfig() *RepositoryConfig {
+	return repoConfig
+}