Merge pull request #106 from vania-pooh/master

Added docs limiting container resources

docs/cli-flags.adoc

@@ -4,6 +4,8 @@ The following flags are supported by ```selenoid``` command:
 ```
 -conf string
     Browsers configuration file (default "config/browsers.json")
+-cpu value
+    Containers cpu limit as float e.g. 0.2 or 1.0
 -disable-docker
     Disable docker support
 -limit int
@@ -12,10 +14,12 @@ The following flags are supported by ```selenoid``` command:
     Network address to accept connections (default ":4444")
 -log-conf string
     Container logging configuration file (default "config/container-logs.json")
+-mem value
+    Containers memory limit e.g. 128m or 1g
 -session-attempt-timeout duration
     New session attempt timeout in time.Duration format (default 30s)
 -session-delete-timeout duration
-    Session delete timeout in time.Duration format (default 30s)    
+    Session delete timeout in time.Duration format (default 30s)
 -timeout duration
     Session idle timeout in time.Duration format (default 1m0s)
 -version

docs/docker-settings.adoc

@@ -6,6 +6,14 @@
 # docker info | grep Storage
 ```
 * Total number of simultaneously running containers (adjusted via ```-limit``` flag) depends on your host machine hardware. Our experience shows that depending on your tests the recommended limit is something like: ```1.5-2.0 x numCores```, where ```numCores``` is total number of cores on your host machine.
+* You may also want to limit memory and CPU consumption for each started container. To do this use ```-mem``` and ```-cpu``` flags. For example to limit memory type:
+
+    # ./selenoid -mem 128m
++
+Here values are specified in https://docs.docker.com/engine/admin/resource_constraints/[Docker format]. Similarly to limit CPU comsumption specify total number of CPUs per container as a float:
+
+    # ./selenoid -cpu 1.5
+
 * We use the same client as `docker` command does. This is why all environment variables like `DOCKER_API_VERSION` or `DOCKER_CERT_PATH` are applicable. See full list of supported variables in https://docs.docker.com/engine/reference/commandline/cli/#environment-variables[Docker documentation]. For example you may encounter the following error when running Selenoid:
 
     [SERVICE_STARTUP_FAILED] [unknown] [create container: Error response from daemon: client is newer than server (client API version: 1.30, server API version: 1.24)]

main.go

@@ -87,8 +87,8 @@ func init() {
 	flag.DurationVar(&newSessionAttemptTimeout, "session-attempt-timeout", 30*time.Second, "New session attempt timeout in time.Duration format")
 	flag.DurationVar(&sessionDeleteTimeout, "session-delete-timeout", 30*time.Second, "Session delete timeout in time.Duration format")
 	flag.BoolVar(&version, "version", false, "Show version and exit")
-	flag.Var(&mem, "mem", "Containers memory limit")
-	flag.Var(&cpu, "cpu", "Containers cpu limit")
+	flag.Var(&mem, "mem", "Containers memory limit e.g. 128m or 1g")
+	flag.Var(&cpu, "cpu", "Containers cpu limit as float e.g. 0.2 or 1.0")
 	flag.Parse()
 
 	if version {