feat: 新增 java run，按 JDK 版本自动套用调优参数运行 Java 应用
- 自动识别 JDK 8/11/17/21 与宿主机 CPU、可用内存；容器内以 cgroup 限额为准；堆默认取可用内存 50%，-Xms 与 -Xmx 同值 - 按版本分支生成参数：JDK 8 用 -Xloggc 一组，JDK 9+ 用 -Xlog:； 堆超过 30g 时自动省略压缩指针参数 - 支持 --jdk/--java/--heap/--xms/--env/--gc-log/--heap-dump-on-oom/ --print-flags/--dry-run；jar 之后的参数原样交给应用 - 前台运行：stdio 直连、退出码透传、SIGINT/SIGTERM 转发给 JVM - BuiltinRequest 增加 Stdin，使内置命令可以读取调用方输入 - 修正帮助中的用法行重复（自定义 Usage 不再追加通用透传尾巴） - 文档：新增 README.java.md，主 README 补充导航与示例
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package executor
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import (
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"fmt"
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"os"
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"strconv"
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"strings"
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)
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// javaTuning is everything BuildJavaFlags needs to describe one JVM launch.
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type javaTuning struct {
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JDK string // normalised release: "8", "11", "17", "21"
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CPUs int // usable CPUs, 0 when unknown
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Memory int64 // usable memory in bytes, 0 when unknown
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Heap string // -Xmx value; empty means "compute from Memory"
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Initial string // -Xms value; empty means "same as -Xmx"
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Env string // used for -Dconfig.file=application-<Env>.yaml
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GCDir string // directory for GC logs; empty means no GC log
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HeapDump bool // add -XX:+HeapDumpOnOutOfMemoryError
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}
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// javaHeapRatio is the fraction of available memory used for the heap when the
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// user does not pick a size: half leaves room for metaspace, thread stacks,
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// direct buffers and the OS page cache.
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const javaHeapRatioPercent = 50
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// compressedOopsLimit is the largest heap for which compressed oops help; JVM
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// warns and effectively disables them beyond this, so kopsc stops emitting the
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// flags at 30 GiB (the commonly recommended ceiling, below the 32 GiB limit).
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const compressedOopsLimit = int64(30) << 30
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// BuildJavaFlags renders the ordered java arguments for one launch.
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//
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// The order mirrors a hand-written command line so `--print-flags` output can
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// be pasted into a Dockerfile or systemd unit unchanged: JVM ergonomics first,
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// then heap, then GC and logging, then application properties.
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func BuildJavaFlags(t javaTuning) []string {
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flags := []string{"-server"}
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// Heap: -Xms and -Xmx are equal to keep the heap from resizing at runtime.
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heapBytes, heapText := resolveHeap(t)
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initialText := t.Initial
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if initialText == "" {
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initialText = heapText
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}
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if heapText != "" {
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flags = append(flags, "-Xmx"+heapText)
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}
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if initialText != "" {
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flags = append(flags, "-Xms"+initialText)
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}
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flags = append(flags,
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"-Xss256k",
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"-XX:MaxDirectMemorySize="+directMemory(heapBytes),
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)
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// Compressed oops only make sense while the heap fits under the limit.
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if heapBytes <= 0 || heapBytes <= compressedOopsLimit {
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flags = append(flags, "-XX:+UseCompressedOops", "-XX:+UseCompressedClassPointers")
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}
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flags = append(flags,
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"-XX:+SegmentedCodeCache",
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"-XX:+UseG1GC",
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"-XX:+ExplicitGCInvokesConcurrent",
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)
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if jdkMajor(t.JDK) >= 9 {
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flags = append(flags, "-XX:+PrintCommandLineFlags")
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if t.GCDir != "" {
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flags = append(flags, "-Xlog:gc*,safepoint:"+gcLogPath(t.GCDir)+":time,uptime:filecount=100,filesize=50M")
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}
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} else {
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// JDK 8 has no -Xlog:; it uses -Xloggc plus its own rotation options.
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// Emitting -Xlog: on JDK 8 makes the JVM refuse to start.
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flags = append(flags, "-verbose:gc", "-XX:+PrintCommandLineFlags", "-XX:+PrintGCDetails", "-XX:+PrintGCDateStamps")
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if t.GCDir != "" {
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flags = append(flags,
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"-Xloggc:"+gcLogPath(t.GCDir),
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"-XX:+UseGCLogFileRotation",
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"-XX:NumberOfGCLogFiles=100",
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"-XX:GCLogFileSize=50M",
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)
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}
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}
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flags = append(flags, "-Djava.security.egd=file:/dev/./urandom")
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if t.HeapDump {
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flags = append(flags, "-XX:+HeapDumpOnOutOfMemoryError")
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}
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flags = append(flags, "-Dconfig.file="+configFile(t.Env))
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return flags
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}
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// configFile renders the Spring-style config property: --env wins, then the
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// APP_ENV environment variable, then "prod".
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func configFile(env string) string {
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if env == "" {
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env = os.Getenv("APP_ENV")
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}
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if env == "" {
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env = "prod"
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}
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return "application-" + env + ".yaml"
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}
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// resolveHeap decides the heap size: an explicit value wins, otherwise half of
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// the available memory.
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func resolveHeap(t javaTuning) (int64, string) {
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if t.Heap != "" {
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return parseJVMSize(t.Heap), t.Heap
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}
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if t.Memory <= 0 {
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return 0, ""
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}
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// Multiply first: dividing by 100 up front truncates, turning 8 GiB into
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// 3.5g because the remainder is lost before the ratio is applied.
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bytes := t.Memory * javaHeapRatioPercent / 100
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return bytes, formatJVMSize(bytes)
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}
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// directMemory returns MaxDirectMemorySize as a quarter of the heap (the JVM's
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// own default), at least 64 MiB so small heaps still work with NIO.
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func directMemory(heapBytes int64) string {
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if heapBytes <= 0 {
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return "256m"
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}
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quarter := heapBytes / 4
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if quarter < 64<<20 {
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quarter = 64 << 20
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}
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return formatJVMSize(quarter)
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}
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// gcLogPath joins the GC directory and the standard file name.
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func gcLogPath(dir string) string {
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return strings.TrimRight(dir, `/\`) + "/gc.log"
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}
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// jdkMajor parses the normalised release into a number; "8" when unknown so
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// the conservative JDK 8 flag set is used.
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func jdkMajor(jdk string) int {
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n, err := strconv.Atoi(strings.TrimSpace(jdk))
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if err != nil {
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return 8
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}
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return n
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}
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// parseJVMSize converts a user-supplied size ("2g", "512m", "1024k", "1073741824")
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// into bytes. An unparsable value returns 0.
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func parseJVMSize(value string) int64 {
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value = strings.TrimSpace(strings.ToLower(value))
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if value == "" {
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return 0
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}
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multiplier := int64(1)
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switch value[len(value)-1] {
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case 'k':
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multiplier, value = 1<<10, value[:len(value)-1]
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case 'm':
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multiplier, value = 1<<20, value[:len(value)-1]
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case 'g':
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multiplier, value = 1<<30, value[:len(value)-1]
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case 't':
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multiplier, value = 1<<40, value[:len(value)-1]
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}
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n, err := strconv.ParseInt(strings.TrimSpace(value), 10, 64)
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if err != nil || n <= 0 {
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return 0
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}
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return n * multiplier
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}
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// formatJVMSize renders bytes the way -Xmx expects: "512m", "2g". Sizes are
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// rounded down to whole mebibytes (or gibibytes when large enough) so the
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// printed flag stays short.
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func formatJVMSize(bytes int64) string {
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if bytes <= 0 {
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return ""
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}
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const (
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mib = int64(1) << 20
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gib = int64(1) << 30
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)
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if bytes >= gib {
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if bytes%gib == 0 {
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return fmt.Sprintf("%dg", bytes/gib)
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}
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// Round down to 0.5g so "6.4g" becomes "6.5g"-free output (6.4g),
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// keeping the flag short while never asking for more than available.
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halfG := int64(1) << 29
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halves := bytes / halfG
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if halves%2 == 0 {
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return fmt.Sprintf("%dg", halves/2)
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}
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return fmt.Sprintf("%.1fg", float64(halves)/2)
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}
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return fmt.Sprintf("%dm", bytes/mib)
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}
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