This developer documentation isoutdated, but provides historical context.

It isnotuser documentation and should not be treated as such.

Documentation is available here.

REST API Using BASH Automation

Introduction

To prepare and regularly refresh a development and/or testing environment for oVirt Engine can be a time-consuming procedure. The REST API can help significantly with the task. This article concentrates on calling oVirt REST API using a BASH scripting from the Linux command line.

It uses:

  • BASH interpreter
  • curl (HTML command line client)
  • xmllint (XPath command line parser)

Supported commands

  • create host server
  • create/import/attach/activate storage domain
  • create virtual machine (VM) and its network, attach image disk and iso disk (CD-ROM)

Basic operations

  • The commands should always check the current state, fetch needed parameters and run the actions only if required, e.g. a host is created from the command, if it doesn’t exist only.
  • The runtime environment is always synchronized with the script state. If the action is asynchronous, it should wait for a given time-out period and periodically check status of the operation by calling the REST API, parsing returned values using XPath processor and checking expected target status value.
  • For HTTPS connection a trusted authority (CA) server certificate is required, else ‘–insecure’ option is to be specified for the curl command.
  • The responses are saved and processed from the specified communication file.

Source code

The script has two parts:

  • general support routines (HTTP method call using curl client, XPath parser)
  • environment synchronization script

For download:

  • rest_api_routines.sh
  • synch_env.sh

Here: TGZ

GitHub sources:

  • git clone <git://github.com/lspevak/ovirt-restapiconf.git>

The following sections contain snipples of code showing the creation of a host in the Engine.

General support routines

XPath support

  • support for getting a value or count of elements selected by a XPath expression in XML file using xmllint tool
# communication file for request/response
COMM_FILE="/tmp/restapi_comm.xml"

# get number of rows returned by XPath expression
function getXPathCount {
    local xPath="count($1)"
    echo $(xmllint --xpath $xPath $COMM_FILE)
}

# get string value of node returned by XPath expression
function getXPathValue {
    local xPath="string($1)"
    echo $(xmllint --xpath $xPath $COMM_FILE)
}

HTTP client support

  • basic support for GET, POST methods using curl client
HEADER_CONTENT_TYPE="Content-Type: application/xml"
HEADER_ACCEPT="Accept: application/xml"

function callGETService {
    local uri=$1
    local certAtt=""

    if [[ -n "$CA_CERT_PATH" ]]; then
        certAtt="--cacert $CA_CERT_PATH"
    fi

    echo "Calling URI (GET): " ${uri}
    curl -X GET -H "${HEADER_ACCEPT}" -H "${HEADER_CONTENT_TYPE}" -u "${USER_NAME}:${USER_PASSW}" "$certAtt" "${ENGINE_URL}${uri}" --output "${COMM_FILE}" 2> /dev/null > "${COMM_FILE}"
}

function callPOSTService {
    local uri=$1
    local xml=$2
    local certAtt=""

    if [[ -n "$CA_CERT_PATH" ]]; then
        certAtt="--cacert $CA_CERT_PATH"
    fi

    echo "Calling URI (POST): " ${uri}
    curl -X POST -H "${HEADER_ACCEPT}" -H "${HEADER_CONTENT_TYPE}" -u "${USER_NAME}:${USER_PASSW}" "$certAtt" "${ENGINE_URL}${uri}" -d "${xml}" 2> /dev/null > "${COMM_FILE}"
}

Waiting for the state with a time-out

  • Asynchronous tasks require a testing of the current state returned by HTTP GET method in cycle.
# wait till XPath returns non-zero number of rows from specified REST API GET service
function waitForStatus {
    local uri=$1
    local xPathStatusTest=$2
    local xPathStatusValue=$3
    local timeoutIntervalSec=$4

    local status="0"
    for i in $(seq 1 10); do
        callGETService "${uri}"
        local c=`getXPathCount "${xPathStatusTest}"`
        local val=`getXPathValue "${xPathStatusValue}"`

        if [[ "$c" > "0" ]]; then
            echo "Target status ${val} reached. Done."
            status="1"
            break;
        else
            echo "Waiting for ${timeoutIntervalSec} s...(${i}, value=${val})"
            sleep ${timeoutIntervalSec}
        fi
    done;

    if [[ "$status" == "0" ]]; then
        echo "Timeout, waiting interrupted."
    fi
}

List hosts and create host actions

# get all hosts
function getHosts {
    callGETService "/api/hosts"
    local c=`getXPathCount "/hosts/host[@id]"`
    echo "Current host count: " ${c}
}

# create host if it doesn't exist
function createHost {
    local hostName=$1
    local hostAddress=$2
    local hostPassword=$3
    local clusterName=$4

    getHosts
    local hostCount=`getXPathCount "/hosts/host[name='${hostName}']"`
    getClusters
    local idCluster=`getXPathValue "/clusters/cluster[name='${clusterName}']/@id"`

    if [[ "${hostCount}" == "0" ]]; then
        echo "Host doesn't exist, creating: ${hostName}..."
        local xml="<host><name>${hostName}</name><address>${hostAddress}</address><root_password>${hostPassword}</root_password><cluster id='${idCluster}' href='/api/clusters/${idCluster}'/></host>"
        callPOSTService "/api/hosts" "${xml}"
        # show response
        cat $COMM_FILE
        # wait for host creation
        waitForStatus "/api/hosts" "/hosts/host[name='${hostName}']/status[state='up']" "/hosts/host[name='${hostName}']/status/state" 10
        echo "Host created."
    else
        echo "Host exists: ${hostName}"
    fi
}

Listing names of objects

  • Using combination of XPath count and XPath string functions, you can iterate e.g. names.
function showList {
    local xPath=$1

    local c=`getXPathCount "${xPath}"`

    for i in $(seq 1 ${c})
    do
        local val=`getXPathValue "(${xPath})[$i]"`
        echo ${val}
    done

    echo "Count: ${c}"
}

...
# show names of configured hosts
function showHostList {
    showList "/hosts/host/name"
}

# show names of configured VMs
function showVMList {
    showList "/vms/vm/name"
}

Environment synchronization script

  • The script uses general routines and describes the target state of your environment.
# configuration of the oVirt engine
ENGINE_URL="http://localhost:8700"
USER_NAME="admin@internal"
USER_PASSW="YOUR_PASSWORD"
# CA certificate path
CA_CERT_PATH=""

echo "Current hosts..."
getHosts

echo "Synchronizing configuration..."
createHost "server1.example.com" "192.168.10.10" "123456" "Default"
createHost "server2.example.com" "192.168.10.11" "123456" "Default"

getHosts
showHostList