Improve stderr drain performance by only record the first 100 lines

Author: orange475

samza-core/src/main/java/org/apache/samza/container/host/PosixCommandBasedStatisticsGetter.java

@@ -35,6 +35,7 @@ public class PosixCommandBasedStatisticsGetter implements SystemStatisticsGetter
 
   private static final Logger log = LoggerFactory.getLogger(PosixCommandBasedStatisticsGetter.class);
   private static final long COMMAND_TIMEOUT_SECONDS = 10;
+  private static final int MAX_ERROR_LINES_TO_CAPTURE = 100;
 
   /**
    * A convenience method to execute shell commands and return all lines of their output.
@@ -60,14 +61,7 @@ private List<String> getAllCommandOutput(String[] cmdArray) throws IOException {
       }
 
       // Consume error stream to prevent blocking
-      StringBuilder errorOutput = new StringBuilder();
-      while ((line = errorReader.readLine()) != null) {
-        errorOutput.append(line).append("\n");
-      }
-
-      if (!line.isEmpty()) {
-        log.error("stderr while running {}: {}", cmdArray, errorOutput);
-      }
+      consumeErrorStream(errorReader, cmdArray);
 
       // Wait for the process to complete to prevent resource leak
       try {
@@ -87,6 +81,37 @@ private List<String> getAllCommandOutput(String[] cmdArray) throws IOException {
     return psOutput;
   }
 
+  /**
+   * Consumes the error stream to prevent process blocking.
+   * Collects first MAX_ERROR_LINES_TO_CAPTURE lines and logs them together if any error output exists.
+   *
+   * @param errorReader the BufferedReader for the error stream
+   * @param cmdArray the command that was executed (for logging context)
+   * @throws IOException if reading from the stream fails
+   */
+  private void consumeErrorStream(BufferedReader errorReader, String[] cmdArray) throws IOException {
+    String line;
+    StringBuilder errorOutput = new StringBuilder();
+    int lineCount = 0;
+    int maxLinesToCapture = MAX_ERROR_LINES_TO_CAPTURE;
+
+    while ((line = errorReader.readLine()) != null) {
+      lineCount++;
+
+      if (lineCount <= maxLinesToCapture) {
+        errorOutput.append(line).append("\n");
+      }
+    }
+
+    if (lineCount > 0) {
+      String errorMessage = errorOutput.toString();
+      if (lineCount > maxLinesToCapture) {
+        errorMessage += String.format("... (%d more lines omitted)", lineCount - maxLinesToCapture);
+      }
+      log.error("Command {} produced error output:\n{}", Arrays.toString(cmdArray), errorMessage);
+    }
+  }
+
   private long getTotalPhysicalMemoryUsageBytes() throws IOException {
     // collect all child process ids of the main process that runs the application
     List<String> processIds = getAllCommandOutput(new String[]{"sh", "-c", "pgrep -P $PPID"});