Embedded Files
PART 1
Strategy Pattern Deep Dive
Context: The "orchestrator" or the part of your application that needs to execute different behaviors based on configuration.
Strategy Interface: Defines the contract for all concrete strategies. This ensures that all strategies can be used interchangeably by the context.
Concrete Strategies: Implementations of the Strategy Interface, each encapsulating a specific behavior or algorithm.
Configuration: The mechanism to select the appropriate strategy at runtime. This could be from a database, configuration file, environment variables, or even user input.
Applying to Database & gRPC
Kotlin
interface DataAccessor {
fun fetchData(): Data // Assuming a common 'Data' type for simplicity
}
class MongoDataAccessor : DataAccessor {
override fun fetchData(): Data {
// MongoDB logic here
}
}
class GrpcDataAccessor : DataAccessor {
override fun fetchData(): Data {
// gRPC call logic here
}
}
// Orchestrator (Context)
class DataOrchestrator(private val config: Config) { // Assume a 'Config' class
fun fetchData(): Data {
val accessor = when (config.dataSource) {
"mongo" -> MongoDataAccessor()
"grpc" -> GrpcDataAccessor()
else -> throw IllegalArgumentException("Invalid data source")
}
return accessor.fetchData()
}
}
Versioning Strategies
Version in Configuration: Include a version identifier in your configuration.
Strategy Naming: Append version numbers to strategy class names (e.g., MongoDataAccessorV1, MongoDataAccessorV2).
Factory Pattern: Use a factory to create strategies based on version and other configuration parameters.
Example with Versioning
Kotlin
// Factory
object DataAccessorFactory {
fun create(config: Config): DataAccessor {
return when (config.dataSource) {
"mongo" -> when (config.version) {
1 -> MongoDataAccessorV1()
2 -> MongoDataAccessorV2()
else -> throw IllegalArgumentException("Invalid version")
}
"grpc" -> GrpcDataAccessor() // Assume no versioning for gRPC for now
else -> throw IllegalArgumentException("Invalid data source")
}
}
}
// Orchestrator using the factory
class DataOrchestrator(private val config: Config) {
fun fetchData(): Data {
val accessor = DataAccessorFactory.create(config)
return accessor.fetchData()
}
}
Key Points
The Strategy pattern promotes loose coupling, making your code more flexible and easier to maintain.
Versioning allows you to evolve your strategies without breaking existing functionality.
Consider combining the Strategy pattern with other patterns like the Factory pattern for more complex scenarios.
Thoroughly test your configuration and versioning logic to ensure correctness.
1. Define Orchestrator Interface and Context
interface Orchestrator {
fun execute(context: OrchestrationContext): OrchestrationContext
}
data class OrchestrationContext(
// ... your data fields here, e.g.,
val requestData: Any,
val intermediateResults: MutableMap<String, Any> = mutableMapOf(),
val errors: MutableList<Exception> = mutableListOf()
)
2. Implement Concrete Strategies with Retry and Resiliency
We'll use the kotlinx-coroutines library for asynchronous operations and retry mechanisms.
Kotlin
import kotlinx.coroutines.*
import kotlinx.coroutines.future.await
import org.springframework.data.mongodb.core.MongoTemplate // Assuming Spring Data MongoDB
import org.springframework.web.client.RestTemplate // For REST API calls
import io.grpc.ManagedChannelBuilder // For gRPC
// ... (other necessary imports)
class MongoDbCallStrategy(private val mongoTemplate: MongoTemplate) : Orchestrator {
override suspend fun execute(context: OrchestrationContext): OrchestrationContext {
return withContext(Dispatchers.IO) {
try {
retry(retries = 3, initialDelayMillis = 1000, maxDelayMillis = 5000, factor = 2.0) {
// ... MongoDB interaction logic using mongoTemplate
// e.g., val result = mongoTemplate.find(...)
context.intermediateResults["mongoDbResult"] = result
}
context
} catch (e: Exception) {
context.copy(errors = context.errors + e)
}
}
}
}
class ExternalRuleEngineCallStrategy(private val restTemplate: RestTemplate) : Orchestrator {
override suspend fun execute(context: OrchestrationContext): OrchestrationContext {
return withContext(Dispatchers.IO) {
try {
retry(retries = 2, initialDelayMillis = 500, maxDelayMillis = 2000, factor = 1.5) {
// ... REST API call to rule engine using restTemplate
// e.g., val response = restTemplate.postForEntity(...)
context.intermediateResults["ruleEngineResult"] = response
}
context
} catch (e: Exception) {
context.copy(errors = context.errors + e)
}
}
}
}
// ... Similarly implement strategies for gRPC calls and other steps
// Helper function for gRPC calls with retry (adjust as needed for your gRPC setup)
suspend fun <T> withGrpcRetry(
channel: ManagedChannel,
retries: Int = 3,
block: suspend (channel: ManagedChannel) -> T
): T {
var currentAttempt = 0
var delayMillis = 1000L
while (currentAttempt < retries) {
try {
return block(channel)
} catch (e: Exception) {
currentAttempt++
if (currentAttempt < retries) {
delay(delayMillis)
delayMillis *= 2
} else {
throw e
}
}
}
throw IllegalStateException("Should never reach here")
}
3. Configuration and Strategy Selection (Unchanged)
The configuration and strategy selection logic remains the same as explained previously.
4. Orchestration Execution with Error Handling
suspend fun executeOrchestration(version: String, initialContext: OrchestrationContext) {
val orchestrators = getOrchestratorForFlow(version)
var context = initialContext
for (orchestrator in orchestrators) {
context = orchestrator.execute(context)
if (context.errors.isNotEmpty()) {
// Handle errors based on your strategy (log, retry specific steps, etc.)
break // Or continue based on your error handling logic
}
}
// ... Handle the final context based on errors or successful completion
}
Important Considerations
Retry Strategies: Customize retry parameters (retries, delays, backoff factors) based on the specific requirements and expected failure modes of each step.
Error Handling: Implement comprehensive error handling at each step and at the orchestration level. Consider logging errors, notifying relevant systems, or taking corrective actions.
Circuit Breakers: For critical external dependencies, consider implementing circuit breaker patterns to prevent cascading failures and protect your system.
Bulkheads: Isolate different parts of your orchestration to prevent failures in one area from impacting the entire system.
Monitoring and Observability: Instrument your orchestration flow with metrics and logs to gain insights into its performance and identify potential issues.
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