github.com/mattyr/nomad@v0.3.3-0.20160919021406-3485a065154a/website/source/docs/drivers/java.html.md (about)

     1  ---
     2  layout: "docs"
     3  page_title: "Drivers: Java"
     4  sidebar_current: "docs-drivers-java"
     5  description: |-
     6    The Java task driver is used to run Jars using the JVM.
     7  ---
     8  
     9  # Java Driver
    10  
    11  Name: `java`
    12  
    13  The `Java` driver is used to execute Java applications packaged into a Java Jar
    14  file. The driver requires the Jar file to be accessible from the Nomad
    15  client via the [`artifact` downloader](/docs/jobspec/index.html#artifact_doc). 
    16  
    17  ## Task Configuration
    18  
    19  The `java` driver supports the following configuration in the job spec:
    20  
    21  * `jar_path` - The path to the downloaded Jar. In most cases this will just be
    22    the name of the Jar. However, if the supplied artifact is an archive that
    23    contains the Jar in a subfolder, the path will need to be the relative path
    24    (`subdir/from_archive/my.jar`).
    25  
    26  *   `args` - (Optional) A list of arguments to the optional `command`.
    27      References to environment variables or any [interpretable Nomad
    28      variables](/docs/jobspec/interpreted.html) will be interpreted
    29      before launching the task. For example:
    30  
    31      ```
    32          args = ["${nomad.datacenter}", "${MY_ENV}", "${meta.foo}"]
    33      ```
    34  
    35  * `jvm_options` - (Optional) A list of JVM options to be passed while invoking
    36    java. These options are passed without being validated in any way by Nomad.
    37  
    38  ## Examples
    39  
    40  A simple config block to run a Java Jar:
    41  
    42  ```
    43  task "web" {
    44    driver = "java"
    45  
    46    config {
    47      jar_path = "local/hello.jar"
    48      jvm_options = ["-Xmx2048m", "-Xms256m"]
    49    }
    50  
    51    # Specifying an artifact is required with the "java"
    52    # driver. This is the # mechanism to ship the Jar to be run.
    53    artifact {
    54      source = "https://dl.dropboxusercontent.com/u/1234/hello.jar"
    55  
    56      options {
    57        checksum = "md5:123445555555555"
    58      }
    59    }
    60  ```
    61  
    62  ## Client Requirements
    63  
    64  The `java` driver requires Java to be installed and in your system's `$PATH`. On 
    65  Linux, Nomad must run as root since it will use `chroot` and `cgroups` which
    66  require root privileges. The task must also specify at least one artifact to
    67  download, as this is the only way to retrieve the Jar being run.
    68  
    69  ## Client Attributes
    70  
    71  The `java` driver will set the following client attributes:
    72  
    73  * `driver.java` - Set to `1` if Java is found on the host node. Nomad determines
    74  this by executing `java -version` on the host and parsing the output
    75  * `driver.java.version` - Version of Java, ex: `1.6.0_65`
    76  * `driver.java.runtime` - Runtime version, ex: `Java(TM) SE Runtime Environment (build 1.6.0_65-b14-466.1-11M4716)`
    77  * `driver.java.vm` - Virtual Machine information, ex: `Java HotSpot(TM) 64-Bit Server VM (build 20.65-b04-466.1, mixed mode)`
    78  
    79  ## Resource Isolation
    80  
    81  The resource isolation provided varies by the operating system of
    82  the client and the configuration.
    83  
    84  On Linux, Nomad will attempt to use cgroups, namespaces, and chroot
    85  to isolate the resources of a process. If the Nomad agent is not
    86  running as root, many of these mechanisms cannot be used.
    87  
    88  As a baseline, the Java jars will be run inside a Java Virtual Machine,
    89  providing a minimum amount of isolation.
    90