Attempting bi-dialect session, assuming Postel's Law holds true on the remote end & Falling back to original OSS JSON using ChromeDriver and Selenium

问题

Below is a snippet of code I'm using to initialize chrome webdriver:

System.out.println("Initializing Chrome");
ChromeOptions options = new ChromeOptions();
//options.setBinary("C:/Program Files (x86)/Google/Chrome/Application");
options.addArguments("start-maximized");
options.setExperimentalOption("excludeSwitches",new String[]{"enable-automation"});
options.addArguments("--disable-extensions");
options.addArguments("--disable-infobars");
options.addArguments("--allow-running-insecure-content");
WDriver = new ChromeDriver(options);
//WDriver = new ChromeDriver();
WDriver.manage().timeouts().implicitlyWait(60,TimeUnit.SECONDS);
System.out.println("Chrome Initialization Complete");

But it seems to be opening two instances of chrome, this is displayed on the console:

Initializing Chrome
Starting ChromeDriver 78.0.3904.70 (edb9c9f3de0247fd912a77b7f6cae7447f6d3ad5-refs/branch- 
heads/3904@{#800}) on port 12262
Only local connections are allowed.
Please protect ports used by ChromeDriver and related test frameworks to prevent access by malicious 
code.
Nov 04, 2019 3:29:38 PM org.openqa.selenium.remote.ProtocolHandshake createSession
INFO: Attempting bi-dialect session, assuming Postel's Law holds true on the remote end
log4j:WARN No appenders could be found for logger 
(org.apache.http.client.protocol.RequestAddCookies).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
[1572910181.451][WARNING]: Timed out connecting to Chrome, retrying...
Nov 04, 2019 3:29:43 PM org.openqa.selenium.remote.ProtocolHandshake createSession
INFO: Falling back to original OSS JSON Wire Protocol.
[1572910186.002][WARNING]: Timed out connecting to Chrome, retrying...
Nov 04, 2019 3:29:48 PM org.openqa.selenium.remote.ProtocolHandshake createSession
INFO: Detected dialect: OSS
Chrome Initialization Complete

Chrome Version: 78.0.3904.87

Chromedriver Version: chromedriver_78.0.3904.70

Selenium Version: 3.141.59

While the issue is not a major roadblock it is a bit annoying that it opens a 2nd instance of chrome that will eat memory while it is on standby.

Cheers.

回答1:

There are a couple of things you need to take care:

This error message...

Nov 04, 2019 3:29:38 PM org.openqa.selenium.remote.ProtocolHandshake createSession
INFO: Attempting bi-dialect session, assuming Postel's Law holds true on the remote end

...implies that the ChromeDriver was unable to initiate/spawn a new WebBrowser i.e. Chrome Browser session.

As per the discussion Attempting bi-dialect session, assuming Postel's Law holds true on the remote end thread 'webdriver dispatcher' panicked at 'index out of bounds: the len is 0 but the index is 0 this issue was observed with Selenium Client v3.0.0-beta3 which was released on 2016-09-01 14:57:03 -0700.

Simon in a comment mentioned that:

The root cause was a ClassCastException. We now catch that exception, log the thing that we were trying to parse and continue with other attempts to complete the handshake. The fix was available in Selenium Client v3.0.0-beta4.

The most appropriate solution would have been to:

Upgrade Selenium to current level of Version 3.141.59.

You can find a detailed discussion in org.openqa.selenium.remote.ProtocolHandshake createSession INFORMATION: Attempting bi-dialect session with Selenium Grid

The next error message...

Nov 04, 2019 3:29:43 PM org.openqa.selenium.remote.ProtocolHandshake createSession
INFO: Falling back to original OSS JSON Wire Protocol.
[1572910186.002][WARNING]: Timed out connecting to Chrome, retrying...
Nov 04, 2019 3:29:48 PM org.openqa.selenium.remote.ProtocolHandshake createSession
INFO: Detected dialect: OSS

...also implies that the ChromeDriver/Chrome Browser combo you are using is not the recent one as the current implementation of ChromeDriver follows W3C and initial logs are as follows:

Starting ChromeDriver 78.0.3904.70 (edb9c9f3de0247fd912a77b7f6cae7447f6d3ad5-refs/branch-heads/3904@{#800}) on port 9626
Only local connections are allowed.
Please protect ports used by ChromeDriver and related test frameworks to prevent access by malicious code.
Nov 05, 2019 3:41:53 PM org.openqa.selenium.remote.ProtocolHandshake createSession
INFO: Detected dialect: W3C

Solution

Ensure that:

JDK is upgraded to current levels JDK 8u222.
Selenium is upgraded to current levels Version 3.141.59.
ChromeDriver is updated to current ChromeDriver v78.0 level.
Chrome is updated to current Chrome Version 78.0 level. (as per ChromeDriver v78.0 release notes)
Clean your Project Workspace through your IDE and Rebuild your project with required dependencies only.
(WindowsOS only) Use CCleaner tool to wipe off all the OS chores before and after the execution of your Test Suite.
(LinuxOS only) Free Up and Release the Unused/Cached Memory in Ubuntu/Linux Mint before and after the execution of your Test Suite.
If your base Web Client version is too old, then uninstall it and install a recent GA and released version of Web Client.
Take a System Reboot.
Execute your @Test as non-root user.
Always invoke driver.quit() within tearDown(){} method to close & destroy the WebDriver and Web Client instances gracefully.

References

You can find some relevant discussion in:

Issue 1504: Unable to Open latest chrome using latest Selenium.
Issue 1451: Chrome 54+ session not created exception: Runtime.executionContextCreated has invalid 'context'

Outro

As per this jar-download.com article the createSession() in ProtocolHandshake.java file of Selenium v3.0.1 contained the following:

public Result createSession(HttpClient client, Command command)
    throws IOException {
    // Avoid serialising the capabilities too many times. Things like profiles are expensive.

    Capabilities desired = (Capabilities) command.getParameters().get("desiredCapabilities");
    desired = desired == null ? new DesiredCapabilities() : desired;
    Capabilities required = (Capabilities) command.getParameters().get("requiredCapabilities");
    required = required == null ? new DesiredCapabilities() : required;

    String des = new BeanToJsonConverter().convert(desired);
    String req = new BeanToJsonConverter().convert(required);

    // Assume the remote end obeys the robustness principle.
    StringBuilder parameters = new StringBuilder("{");
    amendW3CParameters(parameters, des, req);
    parameters.append(",");
    amendOssParamters(parameters, des, req);
    parameters.append("}");
    LOG.info("Attempting bi-dialect session, assuming Postel's Law holds true on the remote end");
    Optional result = createSession(client, parameters);

    // Assume a fragile OSS webdriver implementation
    if (!result.isPresent()) {
      parameters = new StringBuilder("{");
      amendOssParamters(parameters, des, req);
      parameters.append("}");
      LOG.info("Falling back to original OSS JSON Wire Protocol.");
      result = createSession(client, parameters);
    }

    // Assume a fragile w3c implementation
    if (!result.isPresent()) {
      parameters = new StringBuilder("{");
      amendW3CParameters(parameters, des, req);
      parameters.append("}");
      LOG.info("Falling back to straight W3C remote end connection");
      result = createSession(client, parameters);
    }

    if (result.isPresent()) {
      Result toReturn = result.get();
      LOG.info(String.format("Detected dialect: %s", toReturn.dialect));
      return toReturn;
    }

    throw new SessionNotCreatedException(
      String.format(
        "Unable to create new remote session. " +
        "desired capabilities = %s, required capabilities = %s",
        desired,
        required));
}

来源：https://stackoverflow.com/questions/58702552/attempting-bi-dialect-session-assuming-postels-law-holds-true-on-the-remote-en

标签

java

selenium

google-chrome

selenium-webdriver

selenium-chromedriver