Selenium Marionette驱动程序第二次启动时出现UnreachableBrowserException [英] Selenium Marionette driver UnreachableBrowserException upon second launch

问题描述

我目前正在与Selenium Marionette WebDriver玩耍.在我的应用程序中，我想顺序打开多个Marionette驱动程序.基本上是这样的:

I'm currently playing around with the Selenium Marionette WebDriver. In my application, I want to open multiple Marionette drivers sequentially. Basically something like this:

MarionetteDriver driver = new MarionetteDriver();
// do some stuff
driver.quit();

// a while later

driver = new MarionetteDriver();
// do some stuff
driver.quit();

现在，我面临的问题是，只有第一个Marionette实例可以成功启动，对于以后的每次尝试，我都会遇到以下异常.问题每次都会发生，并且使用的端口总是在变化，因此显然没有端口冲突.

Now I'm facing the problem, that only the first Marionette instance can be successfully started and for each later attempt, I'm getting the following exception. The problem happens every time and the used port always changes, so there is obviously no port conflict.

Exception in thread "main" org.openqa.selenium.remote.UnreachableBrowserException: Could not start a new session. Possible causes are invalid address of the remote server or browser start-up failure.
Build info: version: '2.48.2', revision: '41bccdd10cf2c0560f637404c2d96164b67d9d67', time: '2015-10-09 13:08:06'
System info: host: 'qqilihq.local', ip: '192.168.1.2', os.name: 'Mac OS X', os.arch: 'x86_64', os.version: '10.11.2', java.version: '1.7.0_71'
Driver info: driver.version: MarionetteDriver
    at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:641)
    at org.openqa.selenium.remote.RemoteWebDriver.startSession(RemoteWebDriver.java:247)
    at org.openqa.selenium.remote.RemoteWebDriver.startSession(RemoteWebDriver.java:232)
    at org.openqa.selenium.firefox.MarionetteDriver.run(MarionetteDriver.java:84)
    at org.openqa.selenium.firefox.MarionetteDriver.<init>(MarionetteDriver.java:73)
    at org.openqa.selenium.firefox.MarionetteDriver.<init>(MarionetteDriver.java:45)
    at MyMainClass.main(MyMainClass.java:131)
Caused by: org.openqa.selenium.WebDriverException: org.apache.http.conn.HttpHostConnectException: Connect to localhost:41886 [localhost/127.0.0.1, localhost/0:0:0:0:0:0:0:1] failed: Connection refused
Build info: version: '2.48.2', revision: '41bccdd10cf2c0560f637404c2d96164b67d9d67', time: '2015-10-09 13:08:06'
System info: host: 'qqilihq.local', ip: '192.168.1.2', os.name: 'Mac OS X', os.arch: 'x86_64', os.version: '10.11.2', java.version: '1.7.0_71'
Driver info: driver.version: MarionetteDriver
    at org.openqa.selenium.remote.service.DriverCommandExecutor.execute(DriverCommandExecutor.java:91)
    at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:620)
    ... 6 more
Caused by: org.apache.http.conn.HttpHostConnectException: Connect to localhost:41886 [localhost/127.0.0.1, localhost/0:0:0:0:0:0:0:1] failed: Connection refused
    at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:151)
    at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.connect(PoolingHttpClientConnectionManager.java:353)
    at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java:380)
    at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:236)
    at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:184)
    at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:88)
    at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
    at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:184)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:71)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:55)
    at org.openqa.selenium.remote.internal.ApacheHttpClient.fallBackExecute(ApacheHttpClient.java:143)
    at org.openqa.selenium.remote.internal.ApacheHttpClient.execute(ApacheHttpClient.java:89)
    at org.openqa.selenium.remote.HttpCommandExecutor.execute(HttpCommandExecutor.java:142)
    at org.openqa.selenium.remote.service.DriverCommandExecutor.execute(DriverCommandExecutor.java:82)
    ... 7 more
Caused by: java.net.ConnectException: Connection refused
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:579)
    at org.apache.http.conn.socket.PlainConnectionSocketFactory.connectSocket(PlainConnectionSocketFactory.java:74)
    at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.    java:134)
    ... 20 more

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推荐答案

深入研究之后，我发现了以下发现，这些发现最终解决了我的问题:

After digging a little deeper, I came to the following findings which eventually solved my issue:

1. 牵线木偶wires使用两个端口(请参见wires --help)； marionette-port和webdriver-port:

1. Marionette resp. wires uses two ports (see wires --help); a marionette-port and a webdriver-port:

Usage:
    ./wires [OPTIONS]

WebDriver to marionette proxy.

optional arguments:
  -h,--help             show this help message and exit
  -b,--binary BINARY    Path to the Firefox binary
  --webdriver-host WEBDRIVER_HOST
                        Host to run webdriver server on
  --webdriver-port WEBDRIVER_PORT
                        Port to run webdriver on
  --marionette-port MARIONETTE_PORT
                        Port to run marionette on
  --connect-existing    Connect to an existing firefox process

同时运行多个MarionetteDrivers时，两个端口显然必须与已经运行的实例不同.但是，当使用默认构造函数new MarionetteDriver()时，marionette-port保持不变(并且不是根据某些空闲端口确定的).我们为GeckoDriverService.Builder使用了一些变通方法(请参阅下文)，以始终选择两个随机选择的可用端口.

When running multiple MarionetteDrivers simultaneously, both ports have to be different from the already running instance obviously. However, when using the default constructor new MarionetteDriver() the marionette-port remains constant (and is not determined based on some free port). We used some workaround (see below) for the GeckoDriverService.Builder to always pick two randomly-chosen available ports.

当前(版本2.48.2)GeckoDriverService具有waitUntilAvailable()的空实现(应检查WebDriver是否准备就绪).有时，这导致上面发布的UnreachableBrowserException.

The current (version 2.48.2) GeckoDriverService has an empty implementation of waitUntilAvailable() (which should check, if the WebDriver is ready to go). Sporadically, this lead to the UnreachableBrowserException posted above.

为避免这些问题，我们在最后做了这样的事情:

To circumvent these issues, we did something like this at the end:

// determine free ports for Marionette and WebDriver
final int marionettePort = PortProber.findFreePort();
final int webDriverPort = PortProber.findFreePort();
// override, as GeckoDriverService provides no direct way to set the Marionette port
GeckoDriverService.Builder builder = new GeckoDriverService.Builder() {
    @Override
    protected ImmutableList<String> createArgs() {
        Builder<String> argsBuilder = ImmutableList.builder();
        argsBuilder.addAll(super.createArgs());
        argsBuilder.add(String.format("--marionette-port=%d", marionettePort));
        return argsBuilder.build();
    }
};
builder.usingPort(webDriverPort);
builder.usingDriverExecutable(pathToDriver);
GeckoDriverService driverService = builder.build();
try {
    driverService.start();
} catch (IOException e) {
    throw new IllegalStateException("Could not start the GeckoDriverService", e);
}
try {
    // keep checking the WebDriver port via Socket until it's available;
    // as far as I could tell, there is nothing more "high level", e.g. REST API
    waitUntilReady(webDriverPort, TimeUnit.SECONDS.toMillis(30));
} catch (InterruptedException e) {
    // ignore
}
return new MarionetteDriver(driverService, capabilities);

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