0
# Dynamic Compilation and Interpretation
1

2
Dynamic Scala compilation and interpretation capabilities that enable runtime code generation, interactive development, and flexible application behavior modification within Spark applications running on the CDAP platform.
3

4
## Capabilities
5

6
### Default Spark Compiler
7

8
Scala compiler implementation that provides dynamic compilation capabilities for runtime code generation and flexible application behavior.
9

10
```scala { .api }
11
/**
12
 * Default compiler for dynamic Scala code compilation in Spark
13
 * Enables runtime compilation of Scala code within CDAP Spark applications
14
 */
15
class DefaultSparkCompiler extends SparkCompiler {
16
    /**
17
     * Compiles Scala code and returns the resulting class
18
     * @param code Scala source code to compile
19
     * @return Option containing the compiled class, or None if compilation fails
20
     * @throws CompilationException if compilation errors occur
21
     */
22
    def compile(code: String): Option[Class[_]]
23
    
24
    /**
25
     * Compiles Scala code with a specific class name
26
     * @param className Fully qualified name for the compiled class
27
     * @param code Scala source code to compile
28
     * @return Option containing the compiled class, or None if compilation fails
29
     * @throws CompilationException if compilation errors occur
30
     */
31
    def compileClass(className: String, code: String): Option[Class[_]]
32
    
33
    /**
34
     * Compiles multiple Scala source files
35
     * @param sources Map of class names to source code
36
     * @return Map of class names to compiled classes
37
     * @throws CompilationException if compilation errors occur
38
     */
39
    def compileClasses(sources: Map[String, String]): Map[String, Class[_]]
40
    
41
    /**
42
     * Sets the compiler class path
43
     * @param classpath Array of classpath entries
44
     */
45
    def setClassPath(classpath: Array[String]): Unit
46
    
47
    /**
48
     * Gets the current compiler settings
49
     * @return CompilerSettings containing current configuration
50
     */
51
    def getSettings: CompilerSettings
52
    
53
    /**
54
     * Validates Scala code syntax without compilation
55
     * @param code Scala source code to validate
56
     * @return ValidationResult containing validation status and errors
57
     */
58
    def validate(code: String): ValidationResult
59
}
60
```
61

62
### Default Spark Interpreter
63

64
Scala interpreter implementation that provides interactive code execution and REPL-like capabilities within Spark applications.
65

66
```scala { .api }
67
/**
68
 * Default interpreter for dynamic Scala code execution in Spark
69
 * Provides REPL-like capabilities for interactive development
70
 */
71
class DefaultSparkInterpreter extends SparkInterpreter {
72
    /**
73
     * Interprets and executes Scala code
74
     * @param code Scala code to interpret and execute
75
     * @throws InterpretationException if interpretation or execution fails
76
     */
77
    def interpret(code: String): Unit
78
    
79
    /**
80
     * Interprets code and returns the result
81
     * @param code Scala expression to evaluate
82
     * @tparam T Expected return type
83
     * @return Result of the expression evaluation
84
     * @throws InterpretationException if interpretation fails
85
     */
86
    def interpretAndReturn[T](code: String): T
87
    
88
    /**
89
     * Binds a variable to the interpreter context
90
     * @param name Variable name
91
     * @param value Variable value
92
     * @tparam T Type of the value
93
     */
94
    def bind[T](name: String, value: T): Unit
95
    
96
    /**
97
     * Binds a variable with explicit type
98
     * @param name Variable name
99
     * @param tpe Type information
100
     * @param value Variable value
101
     */
102
    def bind(name: String, tpe: String, value: Any): Unit
103
    
104
    /**
105
     * Resets the interpreter state
106
     * Clears all bindings and compiled code
107
     */
108
    def reset(): Unit
109
    
110
    /**
111
     * Gets a bound variable value
112
     * @param name Variable name
113
     * @tparam T Expected type
114
     * @return Variable value
115
     * @throws NoSuchElementException if variable not found
116
     */
117
    def get[T](name: String): T
118
    
119
    /**
120
     * Checks if a variable is bound
121
     * @param name Variable name
122
     * @return true if variable exists in interpreter context
123
     */
124
    def isBound(name: String): Boolean
125
    
126
    /**
127
     * Gets all bound variable names
128
     * @return Set of bound variable names
129
     */
130
    def getBoundNames: Set[String]
131
}
132
```
133

134
### Spark Compiler Interface
135

136
Base interface defining the contract for Spark compiler implementations.
137

138
```scala { .api }
139
/**
140
 * Interface for Spark compiler implementations
141
 * Defines the contract for dynamic Scala compilation
142
 */
143
trait SparkCompiler {
144
    /**
145
     * Compiles Scala source code
146
     * @param code Source code to compile
147
     * @return Option containing compiled class or None if compilation fails
148
     */
149
    def compile(code: String): Option[Class[_]]
150
    
151
    /**
152
     * Compiles code with specific class name
153
     * @param className Target class name
154
     * @param code Source code to compile
155
     * @return Option containing compiled class or None if compilation fails
156
     */
157
    def compileClass(className: String, code: String): Option[Class[_]]
158
    
159
    /**
160
     * Gets compiler configuration settings
161
     * @return Current compiler settings
162
     */
163
    def getSettings: CompilerSettings
164
}
165
```
166

167
### Spark Interpreter Interface
168

169
Base interface defining the contract for Spark interpreter implementations.
170

171
```scala { .api }
172
/**
173
 * Interface for Spark interpreter implementations
174
 * Defines the contract for interactive Scala code execution
175
 */
176
trait SparkInterpreter {
177
    /**
178
     * Interprets and executes Scala code
179
     * @param code Code to interpret
180
     */
181
    def interpret(code: String): Unit
182
    
183
    /**
184
     * Binds a variable to interpreter context
185
     * @param name Variable name
186
     * @param value Variable value
187
     */
188
    def bind(name: String, value: Any): Unit
189
    
190
    /**
191
     * Resets interpreter state
192
     */
193
    def reset(): Unit
194
}
195
```
196

197
## Usage Examples
198

199
**Dynamic Compilation:**
200

201
```scala
202
import co.cask.cdap.app.runtime.spark.dynamic.DefaultSparkCompiler
203

204
// Create compiler instance
205
val compiler = new DefaultSparkCompiler()
206

207
// Set up classpath
208
compiler.setClassPath(Array(
209
    "/path/to/spark-core.jar",
210
    "/path/to/cdap-api.jar"
211
))
212

213
// Compile simple class
214
val code = """
215
class DynamicTransform {
216
  def transform(input: String): String = {
217
    input.toUpperCase.reverse
218
  }
219
}
220
"""
221

222
compiler.compile(code) match {
223
    case Some(clazz) =>
224
        // Create instance and use
225
        val instance = clazz.newInstance()
226
        val method = clazz.getMethod("transform", classOf[String])
227
        val result = method.invoke(instance, "hello world")
228
        println(s"Result: $result") // Result: DLROW OLLEH
229
        
230
    case None =>
231
        println("Compilation failed")
232
}
233

234
// Compile with specific class name
235
val transformerCode = """
236
package com.example
237
class CustomTransformer(multiplier: Int) {
238
  def process(values: Array[Int]): Array[Int] = {
239
    values.map(_ * multiplier)
240
  }
241
}
242
"""
243

244
compiler.compileClass("com.example.CustomTransformer", transformerCode) match {
245
    case Some(clazz) =>
246
        val constructor = clazz.getConstructor(classOf[Int])
247
        val transformer = constructor.newInstance(Int.box(2))
248
        // Use transformer...
249
    case None =>
250
        println("Compilation failed")
251
}
252
```
253

254
**Interactive Interpretation:**
255

256
```scala
257
import co.cask.cdap.app.runtime.spark.dynamic.DefaultSparkInterpreter
258

259
// Create interpreter instance
260
val interpreter = new DefaultSparkInterpreter()
261

262
// Bind variables
263
interpreter.bind("sparkContext", sparkContext)
264
interpreter.bind("inputData", Array(1, 2, 3, 4, 5))
265

266
// Execute code interactively
267
interpreter.interpret("val doubled = inputData.map(_ * 2)")
268
interpreter.interpret("println(s\"Doubled: ${doubled.mkString(', ')}\")")
269

270
// Get results back
271
val result = interpreter.interpretAndReturn[Array[Int]]("doubled")
272
println(s"Result array: ${result.mkString(", ")}")
273

274
// Check bindings
275
if (interpreter.isBound("doubled")) {
276
    val boundValue = interpreter.get[Array[Int]]("doubled")
277
    println(s"Bound value: ${boundValue.mkString(", ")}")
278
}
279

280
// Reset interpreter
281
interpreter.reset()
282
```
283

284
**Spark Integration Example:**
285

286
```scala
287
import org.apache.spark.SparkContext
288
import co.cask.cdap.app.runtime.spark.dynamic.{DefaultSparkCompiler, DefaultSparkInterpreter}
289

290
// Create Spark RDD processing with dynamic code
291
def processWithDynamicCode(sc: SparkContext, 
292
                          data: Array[String], 
293
                          transformCode: String): Array[String] = {
294
    
295
    val compiler = new DefaultSparkCompiler()
296
    
297
    // Compile transform function
298
    val wrapperCode = s"""
299
    class DynamicProcessor {
300
      def process(input: String): String = {
301
        $transformCode
302
      }
303
    }
304
    """
305
    
306
    compiler.compile(wrapperCode) match {
307
        case Some(clazz) =>
308
            // Create RDD and apply dynamic transformation
309
            val rdd = sc.parallelize(data)
310
            val transformedRDD = rdd.map { item =>
311
                val processor = clazz.newInstance()
312
                val method = clazz.getMethod("process", classOf[String])
313
                method.invoke(processor, item).asInstanceOf[String]
314
            }
315
            transformedRDD.collect()
316
            
317
        case None =>
318
            throw new RuntimeException("Failed to compile transformation code")
319
    }
320
}
321

322
// Usage
323
val inputData = Array("apple", "banana", "cherry")
324
val transformCode = "input.toUpperCase + \"_PROCESSED\""
325
val results = processWithDynamicCode(sparkContext, inputData, transformCode)
326
// Results: Array("APPLE_PROCESSED", "BANANA_PROCESSED", "CHERRY_PROCESSED")
327
```
328

329
**REPL-like Development:**
330

331
```scala
332
import co.cask.cdap.app.runtime.spark.dynamic.DefaultSparkInterpreter
333

334
// Create development environment
335
class SparkREPL(sparkContext: SparkContext) {
336
    private val interpreter = new DefaultSparkInterpreter()
337
    
338
    // Initialize with common imports and bindings
339
    interpreter.interpret("import org.apache.spark.SparkContext")
340
    interpreter.interpret("import org.apache.spark.rdd.RDD")
341
    interpreter.bind("sc", sparkContext)
342
    
343
    def execute(code: String): Unit = {
344
        try {
345
            interpreter.interpret(code)
346
        } catch {
347
            case e: Exception => println(s"Error: ${e.getMessage}")
348
        }
349
    }
350
    
351
    def bindData(name: String, data: Any): Unit = {
352
        interpreter.bind(name, data)
353
    }
354
    
355
    def getResult[T](expression: String): T = {
356
        interpreter.interpretAndReturn[T](expression)
357
    }
358
}
359

360
// Usage
361
val repl = new SparkREPL(sparkContext)
362

363
// Bind data
364
repl.bindData("numbers", Array(1, 2, 3, 4, 5))
365

366
// Execute transformations
367
repl.execute("val rdd = sc.parallelize(numbers)")
368
repl.execute("val squares = rdd.map(x => x * x)")
369
repl.execute("val sum = squares.reduce(_ + _)")
370

371
// Get results
372
val finalSum = repl.getResult[Int]("sum")
373
println(s"Sum of squares: $finalSum") // Sum of squares: 55
374
```
375

376
## Types
377

378
```scala { .api }
379
/**
380
 * Compiler configuration settings
381
 */
382
case class CompilerSettings(
383
    /**
384
     * Classpath entries for compilation
385
     */
386
    classpath: Array[String],
387
    
388
    /**
389
     * Output directory for compiled classes
390
     */
391
    outputDirectory: String,
392
    
393
    /**
394
     * Scala compiler options
395
     */
396
    options: Map[String, String],
397
    
398
    /**
399
     * Maximum compilation time in milliseconds
400
     */
401
    maxCompilationTime: Long
402
)
403

404
/**
405
 * Result of code validation
406
 */
407
case class ValidationResult(
408
    /**
409
     * Whether the code is syntactically valid
410
     */
411
    isValid: Boolean,
412
    
413
    /**
414
     * Compilation errors if any
415
     */
416
    errors: List[CompilationError],
417
    
418
    /**
419
     * Compilation warnings if any
420
     */
421
    warnings: List[CompilationWarning]
422
)
423

424
/**
425
 * Compilation error information
426
 */
427
case class CompilationError(
428
    /**
429
     * Error message
430
     */
431
    message: String,
432
    
433
    /**
434
     * Line number where error occurred
435
     */
436
    line: Int,
437
    
438
    /**
439
     * Column number where error occurred
440
     */
441
    column: Int,
442
    
443
    /**
444
     * Severity level of the error
445
     */
446
    severity: ErrorSeverity
447
)
448

449
/**
450
 * Compilation warning information
451
 */
452
case class CompilationWarning(
453
    /**
454
     * Warning message
455
     */
456
    message: String,
457
    
458
    /**
459
     * Line number where warning occurred
460
     */
461
    line: Int,
462
    
463
    /**
464
     * Column number where warning occurred
465
     */
466
    column: Int
467
)
468

469
/**
470
 * Error severity levels
471
 */
472
sealed trait ErrorSeverity
473
object ErrorSeverity {
474
    case object Info extends ErrorSeverity
475
    case object Warning extends ErrorSeverity
476
    case object Error extends ErrorSeverity
477
    case object Fatal extends ErrorSeverity
478
}
479

480
/**
481
 * Exception thrown during compilation
482
 */
483
class CompilationException(message: String, cause: Throwable = null) extends Exception(message, cause)
484

485
/**
486
 * Exception thrown during interpretation
487
 */
488
class InterpretationException(message: String, cause: Throwable = null) extends Exception(message, cause)
489
```