Make it possible to limit number of log lines returned

2 files changed, 6 insertions, 2 deletions

diff --git a/container-core/src/main/java/com/yahoo/container/handler/LogHandler.java b/container-core/src/main/java/com/yahoo/container/handler/LogHandler.java
index c9dc804c46d..72a399744f3 100644
--- a/container-core/src/main/java/com/yahoo/container/handler/LogHandler.java
+++ b/container-core/src/main/java/com/yahoo/container/handler/LogHandler.java
@@ -36,6 +36,8 @@ public class LogHandler extends ThreadedHttpRequestHandler {
                                .map(Long::valueOf).map(Instant::ofEpochMilli).orElse(Instant.MIN);
         Instant to = Optional.ofNullable(request.getProperty("to"))
                              .map(Long::valueOf).map(Instant::ofEpochMilli).orElse(Instant.MAX);
+        long maxLines = Optional.ofNullable(request.getProperty("maxLines"))
+                                .map(Long::valueOf).orElse(100_000L);
         Optional<String> hostname = Optional.ofNullable(request.getProperty("hostname"));
 
         return new AsyncHttpResponse(200) {
@@ -44,7 +46,7 @@ public class LogHandler extends ThreadedHttpRequestHandler {
             @Override
             public void render(OutputStream output, ContentChannel networkChannel, CompletionHandler handler) {
                 try (output) {
-                    logReader.writeLogs(output, from, to, hostname);
+                    logReader.writeLogs(output, from, to, maxLines, hostname);
                 }
                 catch (Throwable t) {
                     log.log(Level.WARNING, "Failed reading logs from " + from + " to " + to, t);
diff --git a/container-core/src/main/java/com/yahoo/container/handler/LogReader.java b/container-core/src/main/java/com/yahoo/container/handler/LogReader.java
index 98f9ee3b79e..dae4b940307 100644
--- a/container-core/src/main/java/com/yahoo/container/handler/LogReader.java
+++ b/container-core/src/main/java/com/yahoo/container/handler/LogReader.java
@@ -59,9 +59,10 @@ class LogReader {
         this.logFilePattern = logFilePattern;
     }
 
-    void writeLogs(OutputStream out, Instant from, Instant to, Optional<String> hostname) {
+    void writeLogs(OutputStream out, Instant from, Instant to, long maxLines, Optional<String> hostname) {
         double fromSeconds = from.getEpochSecond() + from.getNano() / 1e9;
         double toSeconds = to.getEpochSecond() + to.getNano() / 1e9;
+        long linesWritten = 0;
         BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out));
         for (List<Path> logs : getMatchingFiles(from, to)) {
             List<LogLineIterator> logLineIterators = new ArrayList<>();
@@ -73,6 +74,7 @@ class LogReader {
                 Iterator<LineWithTimestamp> lines = Iterators.mergeSorted(logLineIterators,
                                                                           Comparator.comparingDouble(LineWithTimestamp::timestamp));
                 while (lines.hasNext()) {
+                    if (linesWritten++ >= maxLines) return;
                     String line = lines.next().line();
                     writer.write(line);
                     writer.newLine();