Init with alpha version of converter

README.md

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+# Spring Startup To Collapse Stack
+
+spring-startup-to-collapse-stack is CLI tool converting output of 
+[startup endpoint](https://docs.spring.io/spring-boot/docs/current/actuator-api/htmlsingle/#startup)
+to collapse stack format. Collapsed stack can be converted to the flame graph with help of 
+[AsyncProfiler](https://github.com/jvm-profiling-tools/async-profiler).
+
+## Motivation
+
+Spring Boot allows to gather startup metrics since version 
+[2.4.0](https://spring.io/blog/2020/11/12/spring-boot-2-4-0-available-now) 
+([actuator docs](https://docs.spring.io/spring-boot/docs/current/actuator-api/htmlsingle/#startup), 
+[Spring Boot docs](https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#features.spring-application.startup-tracking),
+[Spring Framework docs](https://docs.spring.io/spring-framework/docs/current/reference/html/core.html#context-functionality-startup)).
+However there is lack of tool to visualize where our Spring Boot app spends time during the startup.
+Startup events could be gathered by JFR events and shown in JDK Mission Control:
+![img/jdk-mission-control.png](img.png)
+or can be listed by actuator as a json:
+```json
+{
+  "springBootVersion": "2.5.4",
+  "timeline": {
+    "startTime": "2021-10-09T17:35:50.813987Z",
+    "events": [
+      {
+        "endTime": "2021-10-09T17:35:50.899008Z",
+        "duration": 0.021545,
+        "startupStep": {
+          "name": "spring.boot.application.starting",
+          "id": 0,
+          "tags": [
+            {
+              "key": "mainApplicationClass",
+              "value": "com.github.wyhasany.Application"
+            }
+          ]
+        },
+        "startTime": "2021-10-09T17:35:50.877463Z"
+      },
+      "..."
+    ]
+  }
+}
+```
+Both approaches are troublesome to analyze that data.
+
+We can reinvent the wheel and create new visualization tool as it was tried before (
+[[1]](https://ik.am/eventviewer),
+[[2]](https://alexey-lapin.github.io/spring-boot-startup-analyzer/),
+[[3]](https://spring-boot-startup-analyzer.netlify.app/)).
+Or we can reuse flame graphs which ideally fits for that purpose. That approach has been
+chosen by this project.
+
+Example generated flame graph:
+![img/flamegraph.png](img/flamegraph.png)
+
+### Usage
+
+#### Spring configuration
+
+Configure your app to collect startup events:
+
+```java
+@SpringBootApplication
+public class App {
+    public static void main(String[] args) {
+        new SpringApplicationBuilder()
+            .applicationStartup(new BufferingApplicationStartup(2048))
+            .sources(Application.class)
+            .run(args);
+    }
+}
+```
+
+#### Download startup json
+
+```shell
+curl localhost:8091/actuator/startup > startup.json
+```
+
+#### Download spring-startup-to-collapse-stack converter
+
+#### Convert `startup.json` to collapse format
+
+Keep in mind to use JDK 17
+```shell
+java -jar converter-spring-boot-startup.jar startup.json startup.collapse
+```
+
+#### Convert collapse format to HTML 5 Flame Graph
+```shell
+# Download async-profiler's converter
+curl -L https://github.com/jvm-profiling-tools/async-profiler/releases/download/v2.5/converter.jar --output converter.jar
+# convert to flame graph
+java -cp converter.jar FlameGraph startup.collapse output.html
+```
+
+Open it in browser and explore as other Flame Graphs. 
+
+Note:
+
+Shown samples actually refers to the duration µseconds of given step.

build.gradle

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+plugins {
+    id 'com.github.johnrengelman.shadow' version '7.1.0'
+    id 'java'
+}
+
+group 'com.github.wyhasany'
+version '1.0-SNAPSHOT'
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    implementation 'com.fasterxml.jackson.core:jackson-core:2.13.0'
+    implementation 'com.fasterxml.jackson.core:jackson-databind:2.13.0'
+    testImplementation 'org.assertj:assertj-core:3.21.0'
+    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.8.1'
+    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.8.1'
+}
+
+task testJar(type: Jar) {
+    manifest {
+        attributes 'Main-Class': 'com.github.wyhasany.Main'
+    }
+}
+
+shadowJar {
+    manifest {
+        inheritFrom project.tasks.testJar.manifest
+    }
+    archivesBaseName = 'converter-spring-boot-startup'
+    archiveClassifier = ''
+    archiveVersion = ''
+}
+
+test {
+    useJUnitPlatform()
+}

gradlew

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+#!/usr/bin/env sh
+
+#
+# Copyright 2015 the original author or authors.
+#
+# Licensed 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
+#
+#      https://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.
+#
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MSYS* | MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if [ "$cygwin" = "true" -o "$msys" = "true" ] ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=`expr $i + 1`
+    done
+    case $i in
+        0) set -- ;;
+        1) set -- "$args0" ;;
+        2) set -- "$args0" "$args1" ;;
+        3) set -- "$args0" "$args1" "$args2" ;;
+        4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=`save "$@"`
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+exec "$JAVACMD" "$@"