CAMEL-26929: camel-cli-connector - the trace file starts again at 10 MB, and camel trace and the TUI follow the new file

catalog/camel-catalog/src/generated/resources/org/apache/camel/catalog/docs/cli-connector.adoc

@@ -68,6 +68,10 @@ file is added to it, and with every status it lists it anyway. It also writes th
 phase, such as when it has started, and after it answers actions (at most every 200 millis), so the status shows what
 an action did.
 
+While tracing is on, the connector appends the new traces to `~/.camel/<pid>-trace.json`, one JSON object per line.
+When the file would grow past 10 MB, it starts a new file: a tool that follows the file sees it become smaller, and
+reads the new file from its start.
+
 Write the action file atomically (write a temporary file, then move it), so the connector never reads half an action.
 An action file that cannot be read yet is retried for two seconds. Deleting the action file before the answer is
 written cancels the action.

dsl/camel-cli-connector/src/main/docs/cli-connector.adoc

@@ -68,6 +68,10 @@ file is added to it, and with every status it lists it anyway. It also writes th
 phase, such as when it has started, and after it answers actions (at most every 200 millis), so the status shows what
 an action did.
 
+While tracing is on, the connector appends the new traces to `~/.camel/<pid>-trace.json`, one JSON object per line.
+When the file would grow past 10 MB, it starts a new file: a tool that follows the file sees it become smaller, and
+reads the new file from its start.
+
 Write the action file atomically (write a temporary file, then move it), so the connector never reads half an action.
 An action file that cannot be read yet is retried for two seconds. Deleting the action file before the answer is
 written cancels the action.

dsl/camel-cli-connector/src/main/java/org/apache/camel/cli/connector/FileCliConnectorTransport.java

@@ -98,6 +98,9 @@ public class FileCliConnectorTransport extends ServiceSupport implements CliConn
     private static final long CLOCK_TICK_MS = 20;
     // how often at most the status is written for the actions answered between two snapshots, as collecting it costs
     private static final long ANSWERED_STATUS_MS = 200;
+    // the trace file starts again when it would grow past this: it grew without limit while tracing is on, about 15 MB a
+    // minute at 100 exchanges a second, and camel trace reads it whole (CAMEL-26929)
+    static final long MAX_TRACE_FILE_SIZE = 10 * 1024 * 1024;
 
     private record PendingAction(File output, boolean replyAlways, CompletableFuture<CliActionOutcome> outcome) {
     }
@@ -446,6 +449,20 @@ protected void statusTask() {
         }
     }
 
+    /**
+     * Deletes the file when the data to append would make it larger than the maximum, so the data starts a new file. A
+     * reader that follows the file sees it become smaller, and reads the new file from its start.
+     *
+     * @return whether the file was deleted
+     */
+    static boolean startNewFileIfFull(File file, long append, long max) {
+        long length = file.length();
+        if (length > 0 && length + append > max) {
+            return FileUtil.deleteFile(file);
+        }
+        return false;
+    }
+
     protected void traceTask() {
         try {
             JsonObject json = snapshots.trace();
@@ -462,6 +479,7 @@ protected void traceTask() {
                     // store traces in a special file
                     LOG.trace("Updating trace file: {}", traceFile);
                     String data = json.toJson() + System.lineSeparator();
+                    startNewFileIfFull(traceFile, data.length(), MAX_TRACE_FILE_SIZE);
                     IOHelper.appendText(data, traceFile);
                     json = arr.getMap(arr.size() - 1);
                     traceFilePos = json.getLong("uid");

dsl/camel-cli-connector/src/test/java/org/apache/camel/cli/connector/TraceFileSizeTest.java

@@ -0,0 +1,64 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.camel.cli.connector;
+
+import java.io.File;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * The trace file starts again when it is full, instead of growing while tracing is on (CAMEL-26929).
+ */
+class TraceFileSizeTest {
+
+    @TempDir
+    Path dir;
+
+    @Test
+    void aFileThatWouldGrowPastTheMaximumStartsAgain() throws Exception {
+        File file = Files.writeString(dir.resolve("1-trace.json"), "x".repeat(90)).toFile();
+
+        assertThat(FileCliConnectorTransport.startNewFileIfFull(file, 20, 100)).isTrue();
+        assertThat(file).doesNotExist();
+    }
+
+    @Test
+    void aFileWithRoomIsAppendedTo() throws Exception {
+        File file = Files.writeString(dir.resolve("1-trace.json"), "x".repeat(50)).toFile();
+
+        assertThat(FileCliConnectorTransport.startNewFileIfFull(file, 20, 100)).isFalse();
+        assertThat(file).hasContent("x".repeat(50));
+    }
+
+    @Test
+    void anEmptyFileTakesDataLargerThanTheMaximum() throws Exception {
+        // a single snapshot larger than the maximum is still written
+        File file = dir.resolve("1-trace.json").toFile();
+
+        assertThat(FileCliConnectorTransport.startNewFileIfFull(file, 200, 100)).isFalse();
+    }
+
+    @Test
+    void theMaximumIsTenMegabytes() {
+        assertThat(FileCliConnectorTransport.MAX_TRACE_FILE_SIZE).isEqualTo(10L * 1024 * 1024);
+    }
+}

dsl/camel-jbang/camel-jbang-core/src/main/java/org/apache/camel/dsl/jbang/core/commands/action/CamelTraceAction.java

@@ -514,13 +514,19 @@ private int readTraceFiles(Map<Long, Pid> pids) throws Exception {
         int lines = 0;
 
         for (Pid pid : pids.values()) {
+            Path file = getTraceFile(pid.pid);
+            long size = Files.exists(file) ? Files.size(file) : 0;
+            if (pid.reader != null && isNewFile(pid.size, size)) {
+                // the integration started a new trace file, as the old one was full: read the new one from its start
+                IOHelper.close(pid.reader);
+                pid.reader = new LineNumberReader(Files.newBufferedReader(file));
+            }
+            pid.size = size;
             if (pid.reader == null) {
-                Path file = getTraceFile(pid.pid);
                 if (Files.exists(file)) {
                     pid.reader = new LineNumberReader(Files.newBufferedReader(file));
                     if (tail == 0) {
                         // only read new lines so forward to end of reader
-                        long size = Files.size(file);
                         pid.reader.skip(size);
                     }
                 }
@@ -549,6 +555,13 @@ private int readTraceFiles(Map<Long, Pid> pids) throws Exception {
         return lines;
     }
 
+    /**
+     * Whether a file that a reader follows was started again: it is smaller than when it was last read (CAMEL-26929).
+     */
+    static boolean isNewFile(long lastSize, long size) {
+        return size < lastSize;
+    }
+
     private List<Row> parseTraceLine(Pid pid, String line) {
         JsonObject root = null;
         try {
@@ -942,6 +955,8 @@ private static class Pid {
         Queue<String> fifo;
         int depth;
         LineNumberReader reader;
+        // the size of the trace file when it was last read
+        long size;
     }
 
     private static class Row {

dsl/camel-jbang/camel-jbang-core/src/test/java/org/apache/camel/dsl/jbang/core/commands/action/CamelTraceActionTest.java

@@ -277,4 +277,13 @@ private static JsonObject status(boolean enabled, boolean standby) {
         root.put("trace", trace);
         return root;
     }
+
+    @Test
+    void aTraceFileThatGotSmallerIsANewFile() {
+        // CAMEL-26929: the integration starts a new trace file when it is full, and camel trace reads it from its start
+        assertThat(CamelTraceAction.isNewFile(10_000, 120)).isTrue();
+        assertThat(CamelTraceAction.isNewFile(10_000, 10_000)).isFalse();
+        assertThat(CamelTraceAction.isNewFile(10_000, 12_000)).isFalse();
+        assertThat(CamelTraceAction.isNewFile(0, 120)).isFalse();
+    }
 }

dsl/camel-jbang/camel-jbang-plugin-tui/src/main/java/org/apache/camel/dsl/jbang/core/commands/tui/DataRefreshService.java

@@ -668,6 +668,14 @@ void refreshTraceData(List<Long> pids) {
         traces.set(allTraces);
     }
 
+    /**
+     * Where to read a file that grows on from: the position read up to, or the start when the file is smaller than
+     * that, as the integration started a new trace file when it was full (CAMEL-26929).
+     */
+    static long readFrom(long lastPos, long length) {
+        return length < lastPos ? 0 : lastPos;
+    }
+
     private void readTraceFile(String pid, List<TraceEntry> allTraces) {
         Path traceFile = CommandLineHelper.getCamelDir().resolve(pid + "-trace.json");
         if (!Files.exists(traceFile)) {
@@ -678,6 +686,7 @@ private void readTraceFile(String pid, List<TraceEntry> allTraces) {
 
         try (RandomAccessFile raf = new RandomAccessFile(traceFile.toFile(), "r")) {
             long length = raf.length();
+            lastPos = readFrom(lastPos, length);
             if (length <= lastPos) {
                 return; // no new data
             }

dsl/camel-jbang/camel-jbang-plugin-tui/src/test/java/org/apache/camel/dsl/jbang/core/commands/tui/DataRefreshMembershipTest.java

@@ -169,4 +169,12 @@ public boolean isInfraSelected() {
                 },
                 Path::of, Path::of);
     }
+
+    @Test
+    void aTraceFileThatGotSmallerIsReadFromItsStart() {
+        // CAMEL-26929: the integration starts a new trace file when it is full; the panel read nothing from it again
+        assertThat(DataRefreshService.readFrom(10_000, 120)).isZero();
+        assertThat(DataRefreshService.readFrom(10_000, 12_000)).isEqualTo(10_000);
+        assertThat(DataRefreshService.readFrom(0, 120)).isZero();
+    }
 }