[V3 Audio] Harden Lavalink boot sequence (#1498)

* Do a bit of hardening

* Loop not asyncio

* Don't use new asyncio coolness

* I hate you all

* Muck up everything

* Fix version comparisons

redbot/cogs/audio/manager.py

@@ -1,12 +1,22 @@
 import shlex
+import shutil
 import asyncio
-from subprocess import Popen, DEVNULL
+from subprocess import Popen, DEVNULL, PIPE
 import os
+import logging
+
+log = logging.getLogger('red.audio.manager')
 
 proc = None
 SHUTDOWN = asyncio.Event()
 
 
+def has_java_error(pid):
+    from . import LAVALINK_DOWNLOAD_DIR
+    poss_error_file = LAVALINK_DOWNLOAD_DIR / 'hs_err_pid{}.log'.format(pid)
+    return poss_error_file.exists()
+
+
 async def monitor_lavalink_server(loop):
     while not SHUTDOWN.is_set():
         if proc.poll() is not None:
@@ -14,13 +24,55 @@ async def monitor_lavalink_server(loop):
         await asyncio.sleep(0.5)
 
     if not SHUTDOWN.is_set():
-        print("Lavalink jar shutdown, restarting.")
-        await start_lavalink_server(loop)
+        log.info("Lavalink jar shutdown.")
+        if not has_java_error(proc.pid):
+            log.info("Restarting Lavalink jar.")
+            await start_lavalink_server(loop)
+        else:
+            log.error("Your Java is borked. Please find the hs_err_pid{}.log file"
+                      " in the Audio data folder and report this issue.".format(
+                proc.pid
+            ))
 
 
+async def has_java(loop):
+    java_available = shutil.which('java') is not None
+    if not java_available:
+        return False
+
+    version = await get_java_version(loop)
+    return version >= (1, 8), version
+
+
+async def get_java_version(loop):
+    """
+    This assumes we've already checked that java exists.
+    """
+    proc = Popen(
+        shlex.split("java -version", posix=os.name == 'posix'),
+        stdout=PIPE, stderr=PIPE
+    )
+    _, err = proc.communicate()
+
+    version_info = str(err, encoding='utf-8')
+
+    version_line = version_info.split('\n')[0]
+    version_start = version_line.find('"')
+    version_string = version_line[version_start + 1:-1]
+    major, minor = version_string.split('.')[:2]
+    return int(major), int(minor)
+
 async def start_lavalink_server(loop):
+    java_available, java_version = await has_java(loop)
+    if not java_available:
+        raise RuntimeError("You must install Java 1.8+ for Lavalink to run.")
+
+    extra_flags = ""
+    if java_version == (1, 8):
+        extra_flags = "-Dsun.zip.disableMemoryMapping=true"
+
     from . import LAVALINK_DOWNLOAD_DIR, LAVALINK_JAR_FILE
-    start_cmd = "java -jar {}".format(LAVALINK_JAR_FILE.resolve())
+    start_cmd = "java {} -jar {}".format(extra_flags, LAVALINK_JAR_FILE.resolve())
 
     global proc
     proc = Popen(
@@ -29,13 +81,15 @@ async def start_lavalink_server(loop):
         stdout=DEVNULL, stderr=DEVNULL
     )
 
-    print("Lavalink jar started. PID: {}".format(proc.pid))
+    log.info("Lavalink jar started. PID: {}".format(proc.pid))
 
     loop.create_task(monitor_lavalink_server(loop))
 
 
 def shutdown_lavalink_server():
-    print("Shutting down lavalink server.")
+    log.info("Shutting down lavalink server.")
     SHUTDOWN.set()
+    global proc
     if proc is not None:
         proc.terminate()
+        proc = None