Q:

Webdriver.io session not created: Unable to create new service: GeckoDriverService

I am running my initial project setup for Webdriver.io, I was able to run tests earlier but now getting errors which are related to geckodrivers or capabilities I am not understanding.
I have tried finding an issue with geckodriver and finding geckodriver version in that I am getting some errors as below:
geckodriver -v
1559030261896   geckodriver ERROR   Address in use (os error 98)
wdio.conf.js:
exports.config = {
    //
    // ====================
    // Runner Configuration
    // ====================
    //
    // WebdriverIO allows it to run your tests in arbitrary locations (e.g. locally or
    // on a remote machine).
    runner: 'local',
    //
    // ==================
    // Specify Test Files
    // ==================
    // Define which test specs should run. The pattern is relative to the directory
    // from which `wdio` was called. Notice that, if you are calling `wdio` from an
    // NPM script (see https://docs.npmjs.com/cli/run-script) then the current working
    // directory is where your package.json resides, so `wdio` will be called from there.
    //
    specs: [
        './test/test-specs/**/*.specs.js'
    ],
    // Patterns to exclude.
    exclude: [
        // 'path/to/excluded/files'
    ],
    //
    // ============
    // Capabilities
    // ============
    // Define your capabilities here. WebdriverIO can run multiple capabilities at the same
    // time. Depending on the number of capabilities, WebdriverIO launches several test
    // sessions. Within your capabilities you can overwrite the spec and exclude options in
    // order to group specific specs to a specific capability.
    //
    // First, you can define how many instances should be started at the same time. Let's
    // say you have 3 different capabilities (Chrome, Firefox, and Safari) and you have
    // set maxInstances to 1; wdio will spawn 3 processes. Therefore, if you have 10 spec
    // files and you set maxInstances to 10, all spec files will get tested at the same time
    // and 30 processes will get spawned. The property handles how many capabilities
    // from the same test should run tests.
    //
    maxInstances: 10,
    maxInstancesPerCapability: 10,
    //
    // If you have trouble getting all important capabilities together, check out the
    // Sauce Labs platform configurator - a great tool to configure your capabilities:
    // https://docs.saucelabs.com/reference/platforms-configurator
    //
    capabilities: [{
        // maxInstances can get overwritten per capability. So if you have an in-house Selenium
        // grid with only 5 firefox instances available you can make sure that not more than
        // 5 instances get started at a time.
        //maxInstances: 5,
        //
        browserName: 'firefox',
        // If outputDir is provided WebdriverIO can capture driver session logs
        // it is possible to configure which logTypes to include/exclude.
        // excludeDriverLogs: ['*'], // pass '*' to exclude all driver session logs
        // excludeDriverLogs: ['bugreport', 'server'],
    }],
    //
    // ===================
    // Test Configurations
    // ===================
    // Define all options that are relevant for the WebdriverIO instance here
    //
    // Level of logging verbosity: trace | debug | info | warn | error | silent
    logLevel: 'error',
    //
    // Set specific log levels per logger
    // loggers:
    // - webdriver, webdriverio
    // - @wdio/applitools-service, @wdio/browserstack-service, @wdio/devtools-service, @wdio/sauce-service
    // - @wdio/mocha-framework, @wdio/jasmine-framework
    // - @wdio/local-runner, @wdio/lambda-runner
    // - @wdio/sumologic-reporter
    // - @wdio/cli, @wdio/config, @wdio/sync, @wdio/utils
    // Level of logging verbosity: trace | debug | info | warn | error | silent
    // logLevels: {
        // webdriver: 'info',
        // '@wdio/applitools-service': 'info'
    // },
    //
    // If you only want to run your tests until a specific amount of tests have failed use
    // bail (default is 0 - don't bail, run all tests).
    bail: 0,
    //
    // Set a base URL in order to shorten url command calls. If your `url` parameter starts
    // with `/`, the base url gets prepended, not including the path portion of your baseUrl.
    // If your `url` parameter starts without a scheme or `/` (like `some/path`), the base url
    // gets prepended directly.
    baseUrl: '<my base url>',
    //
    // Default timeout for all waitFor* commands.
    waitforTimeout: 10000,
    //
    // Default timeout in milliseconds for request
    // if Selenium Grid doesn't send response
    connectionRetryTimeout: 90000,
    //
    // Default request retries count
    connectionRetryCount: 3,
    //
    // Test runner services
    // Services take over a specific job you don't want to take care of. They enhance
    // your test setup with almost no effort. Unlike plugins, they don't add new
    // commands. Instead, they hook themselves up into the test process.
    services: ['selenium-standalone'],
    //
    // Framework you want to run your specs with.
    // The following are supported: Mocha, Jasmine, and Cucumber
    // see also: https://webdriver.io/docs/frameworks.html
    //
    // Make sure you have the wdio adapter package for the specific framework installed
    // before running any tests.
    framework: 'mocha',
    //
    // The number of times to retry the entire specfile when it fails as a whole
    // specFileRetries: 1,
    //
    // Test reporter for stdout.
    // The only one supported by default is 'dot'
    // see also: https://webdriver.io/docs/dot-reporter.html
    reporters: ['spec'],

    //
    // Options to be passed to Mocha.
    // See the full list at http://mochajs.org/
    mochaOpts: {
        ui: 'bdd',
        timeout: 100000
    },
    //
    // =====
    // Hooks
    // =====
    // WebdriverIO provides several hooks you can use to interfere with the test process in order to enhance
    // it and to build services around it. You can either apply a single function or an array of
    // methods to it. If one of them returns with a promise, WebdriverIO will wait until that promise got
    // resolved to continue.
    /**
     * Gets executed once before all workers get launched.
     * @param {Object} config wdio configuration object
     * @param {Array.<Object>} capabilities list of capabilities details
     */
    // onPrepare: function (config, capabilities) {
    // },
    /**
     * Gets executed just before initialising the webdriver session and test framework. It allows you
     * to manipulate configurations depending on the capability or spec.
     * @param {Object} config wdio configuration object
     * @param {Array.<Object>} capabilities list of capabilities details
     * @param {Array.<String>} specs List of spec file paths that are to be run
     */
    // beforeSession: function (config, capabilities, specs) {
    // },
    /**
     * Gets executed before test execution begins. At this point you can access to all global
     * variables like `browser`. It is the perfect place to define custom commands.
     * @param {Array.<Object>} capabilities list of capabilities details
     * @param {Array.<String>} specs List of spec file paths that are to be run
     */
    // before: function (capabilities, specs) {
    // },
    /**
     * Runs before a WebdriverIO command gets executed.
     * @param {String} commandName hook command name
     * @param {Array} args arguments that command would receive
     */
    // beforeCommand: function (commandName, args) {
    // },

    /**
     * Hook that gets executed before the suite starts
     * @param {Object} suite suite details
     */
    // beforeSuite: function (suite) {
    // },
    /**
     * Function to be executed before a test (in Mocha/Jasmine) or a step (in Cucumber) starts.
     * @param {Object} test test details
     */
    // beforeTest: function (test) {
    // },
    /**
     * Hook that gets executed _before_ a hook within the suite starts (e.g. runs before calling
     * beforeEach in Mocha)
     */
    // beforeHook: function () {
    // },
    /**
     * Hook that gets executed _after_ a hook within the suite starts (e.g. runs after calling
     * afterEach in Mocha)
     */
    // afterHook: function () {
    // },
    /**
     * Function to be executed after a test (in Mocha/Jasmine) or a step (in Cucumber) starts.
     * @param {Object} test test details
     */
    // afterTest: function (test) {
    // },
    /**
     * Hook that gets executed after the suite has ended
     * @param {Object} suite suite details
     */
    // afterSuite: function (suite) {
    // },

    /**
     * Runs after a WebdriverIO command gets executed
     * @param {String} commandName hook command name
     * @param {Array} args arguments that command would receive
     * @param {Number} result 0 - command success, 1 - command error
     * @param {Object} error error object if any
     */
    // afterCommand: function (commandName, args, result, error) {
    // },
    /**
     * Gets executed after all tests are done. You still have access to all global variables from
     * the test.
     * @param {Number} result 0 - test pass, 1 - test fail
     * @param {Array.<Object>} capabilities list of capabilities details
     * @param {Array.<String>} specs List of spec file paths that ran
     */
    // after: function (result, capabilities, specs) {
    // },
    /**
     * Gets executed right after terminating the webdriver session.
     * @param {Object} config wdio configuration object
     * @param {Array.<Object>} capabilities list of capabilities details
     * @param {Array.<String>} specs List of spec file paths that ran
     */
    // afterSession: function (config, capabilities, specs) {
    // },
    /**
     * Gets executed after all workers got shut down and the process is about to exit.
     * @param {Object} exitCode 0 - success, 1 - fail
     * @param {Object} config wdio configuration object
     * @param {Array.<Object>} capabilities list of capabilities details
     * @param {<Object>} results object containing test results
     */
    // onComplete: function(exitCode, config, capabilities, results) {
    // },
    /**
    * Gets executed when a refresh happens.
    * @param {String} oldSessionId session ID of the old session
    * @param {String} newSessionId session ID of the new session
    */
    //onReload: function(oldSessionId, newSessionId) {
    //}
}

Tests should be running with specs file provided. but getting error as below:
> webdriverio-test@1.0.0 test /home/apaliwal/Solution-Engine-new/new-solution-engine-test
> wdio wdio.conf.js

Execution of 1 spec files started at 2019-05-28T08:04:11.842Z

[0-0] RUNNING in firefox - /test/test-specs/login.specs.js
[0-0] 2019-05-28T08:04:16.698Z ERROR webdriver: Request failed due to session not created: Unable to create new service: GeckoDriverService
Build info: version: '3.141.59', revision: 'e82be7d358', time: '2018-11-14T08:25:53'
System info: host: 'localhost.localdomain', ip: '127.0.0.1', os.name: 'Linux', os.arch: 'amd64', os.version: '5.0.16-200.fc29.x86_64', java.version: '1.8.0_212'
Driver info: driver.version: unknown
    at getErrorFromResponseBody (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/webdriver/build/utils.js:349:10)
    at Request._callback (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/webdriver/build/request.js:121:64)
    at Request.self.callback (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/request/request.js:185:22)
    at Request.emit (events.js:189:13)
    at Request.EventEmitter.emit (domain.js:441:20)
    at Request.<anonymous> (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/request/request.js:1161:10)
    at Request.emit (events.js:189:13)
    at Request.EventEmitter.emit (domain.js:441:20)
    at IncomingMessage.<anonymous> (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/request/request.js:1083:12)
    at Object.onceWrapper (events.js:277:13)
[0-0] 2019-05-28T08:04:16.701Z ERROR @wdio/runner: session not created: Unable to create new service: GeckoDriverService
Build info: version: '3.141.59', revision: 'e82be7d358', time: '2018-11-14T08:25:53'
System info: host: 'localhost.localdomain', ip: '127.0.0.1', os.name: 'Linux', os.arch: 'amd64', os.version: '5.0.16-200.fc29.x86_64', java.version: '1.8.0_212'
Driver info: driver.version: unknown
    at getErrorFromResponseBody (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/webdriver/build/utils.js:349:10)
    at Request._callback (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/webdriver/build/request.js:121:64)
    at Request.self.callback (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/request/request.js:185:22)
    at Request.emit (events.js:189:13)
    at Request.EventEmitter.emit (domain.js:441:20)
    at Request.<anonymous> (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/request/request.js:1161:10)
    at Request.emit (events.js:189:13)
    at Request.EventEmitter.emit (domain.js:441:20)
    at IncomingMessage.<anonymous> (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/request/request.js:1083:12)
    at Object.onceWrapper (events.js:277:13)
0-0 worker error { name: 'session not created',
  message:
   'Unable to create new service: GeckoDriverService\nBuild info: version: \'3.141.59\', revision: \'e82be7d358\', time: \'2018-11-14T08:25:53\'\nSystem info: host: \'localhost.localdomain\', ip: \'127.0.0.1\', os.name: \'Linux\', os.arch: \'amd64\', os.version: \'5.0.16-200.fc29.x86_64\', java.version: \'1.8.0_212\'\nDriver info: driver.version: unknown',
  stack:
   'session not created: Unable to create new service: GeckoDriverService\nBuild info: version: \'3.141.59\', revision: \'e82be7d358\', time: \'2018-11-14T08:25:53\'\nSystem info: host: \'localhost.localdomain\', ip: \'127.0.0.1\', os.name: \'Linux\', os.arch: \'amd64\', os.version: \'5.0.16-200.fc29.x86_64\', java.version: \'1.8.0_212\'\nDriver info: driver.version: unknown\n    at getErrorFromResponseBody (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/webdriver/build/utils.js:349:10)\n    at Request._callback (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/webdriver/build/request.js:121:64)\n    at Request.self.callback (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/request/request.js:185:22)\n    at Request.emit (events.js:189:13)\n    at Request.EventEmitter.emit (domain.js:441:20)\n    at Request.<anonymous> (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/request/request.js:1161:10)\n    at Request.emit (events.js:189:13)\n    at Request.EventEmitter.emit (domain.js:441:20)\n    at IncomingMessage.<anonymous> (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/request/request.js:1083:12)\n    at Object.onceWrapper (events.js:277:13)' }
[0-0] 2019-05-28T08:04:16.702Z ERROR @wdio/local-runner: Failed launching test session: TypeError: Cannot read property 'capabilities' of null
    at Runner.run (/home/apaliwal/Solution-Engine-new/new-solution-engine-test/node_modules/@wdio/runner/build/index.js:91:74)
    at process._tickCallback (internal/process/next_tick.js:68:7)
[0-0] FAILED in firefox - /test/test-specs/login.specs.js

Spec Files:  0 passed, 1 failed, 1 total (100% completed) in 00:00:04 

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! webdriverio-test@1.0.0 test: `wdio wdio.conf.js`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the webdriverio-test@1.0.0 test script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/apaliwal/.npm/_logs/2019-05-28T08_04_16_722Z-debug.log

A:

The error you are seeing does gives us some hint about whats going wrong as follows :
ERROR @wdio/runner: session not created: Unable to create new service: GeckoDriverService
Build info: version: '3.141.59', revision: 'e82be7d358', time: '2018-11-14T08:25:53'
System info: host: 'localhost.localdomain', ip: '127.0.0.1', os.name: 'Linux', os.arch: 'amd64', os.version: '5.0.16-200.fc29.x86_64', java.version: '1.8.0_212'
Driver info: driver.version: unknown

It is clear from the error message that a new GeckoDriverService is not getting initiated as you see the log message as Driver info: driver.version: unknown. The main reason of this error can be the incompatibility between the binaries you are using.

Your Selenium Client version is 3.141.59.
Your GeckoDriver version  is unknown to us.
Your Firefox browser version  is unknown to us.

Solution
A quick solution would be to :

Update GeckoDriver version to recent levels i.e. GeckoDriver v0.24.0
Update Firefox version to recent levels i.e. Firefox v67.0

Follow the GeckoDriver, Selenium and Firefox Browser compatibility chart as depicted below.

If your base version of Firefox is older uninstall Firefox and install a recent GA released version of Firefox
Execute your Test.

GeckoDriver, Selenium and Firefox Browser compatibility chart

