Discovery Patterns for ServiceNow
Discovery automatically populates the CMDB by scanning networks and systems.
Discovery Architecture
Discovery Schedule
↓
MID Server
↓
Probes (collect data)
↓
Sensors (process data)
↓
Identification Rules (match/create CIs)
↓
CMDB Population
Key Tables
| Table | Purpose |
|---|
discovery_schedule | Discovery schedules |
discovery_credentials | Discovery credentials |
discovery_range | IP ranges to scan |
cmdb_identification_rule | CI identification |
ecc_agent | MID Server records |
discovery_status | Discovery run status |
Discovery Schedules (ES5)
Create Discovery Schedule
// Create discovery schedule (ES5 ONLY!)
var schedule = new GlideRecord("discovery_schedule")
schedule.initialize()
// Basic info
schedule.setValue("name", "Data Center Discovery")
schedule.setValue("description", "Weekly discovery of data center infrastructure")
// Type
schedule.setValue("discover", "IP") // IP, CI, Cloud Resources
// Schedule
schedule.setValue("run_type", "weekly")
schedule.setValue("run_dayofweek", "sunday")
schedule.setValue("run_time", "02:00:00")
// MID Server
schedule.setValue("mid_server", getMIDServerSysId("DataCenterMID"))
// Enable
schedule.setValue("active", true)
var scheduleSysId = schedule.insert()
// Add IP range
addDiscoveryRange(scheduleSysId, "10.0.0.0", "10.0.255.255", "Data Center Network")
Add Discovery Range
// Add IP range to discovery schedule (ES5 ONLY!)
function addDiscoveryRange(scheduleSysId, startIP, endIP, name) {
var range = new GlideRecord("discovery_range")
range.initialize()
range.setValue("schedule", scheduleSysId)
range.setValue("name", name)
range.setValue("type", "range")
range.setValue("range_start", startIP)
range.setValue("range_end", endIP)
range.setValue("active", true)
return range.insert()
}
// Add CIDR range
function addDiscoveryCIDR(scheduleSysId, cidr, name) {
var range = new GlideRecord("discovery_range")
range.initialize()
range.setValue("schedule", scheduleSysId)
range.setValue("name", name)
range.setValue("type", "cidr")
range.setValue("range", cidr) // e.g., '10.0.0.0/24'
range.setValue("active", true)
return range.insert()
}
Discovery Credentials (ES5)
Create Credentials
// Create Windows credential (ES5 ONLY!)
var cred = new GlideRecord("discovery_credentials")
cred.initialize()
cred.setValue("name", "Windows Domain Admin")
cred.setValue("type", "windows")
cred.setValue("user_name", "domain\\admin")
cred.setValue("password", "") // Set via secure method
cred.setValue("active", true)
// Credential order
cred.setValue("order", 100)
// Assign to credential affinity
cred.setValue("credential_alias", credentialAliasSysId)
cred.insert()
Credential Affinity
// Create credential affinity (map credentials to IP ranges) (ES5 ONLY!)
var affinity = new GlideRecord("dscy_credentials_affinity")
affinity.initialize()
affinity.setValue("credential", credentialSysId)
affinity.setValue("range", discoveryRangeSysId)
affinity.setValue("order", 100)
affinity.insert()
Custom Probes and Sensors (ES5)
Custom Probe
// Create custom probe script (ES5 ONLY!)
// Probes run on MID Server to collect data
// Table: discovery_probes_script
var probe = new GlideRecord("discovery_probes_script")
probe.initialize()
probe.setValue("name", "Custom Application Version")
probe.setValue("active", true)
// Probe script (runs on MID Server - ES5 ONLY!)
probe.setValue(
"script",
"var output = {};\n" +
"\n" +
"// Command to run\n" +
'var cmd = "cat /opt/myapp/version.txt";\n' +
"\n" +
"try {\n" +
" var result = Packages.com.service_now.mid.probe.tpcon.OperatingSystemCommand.execute(cmd);\n" +
" output.app_version = result.getOutput().trim();\n" +
" output.success = true;\n" +
"} catch (e) {\n" +
" output.success = false;\n" +
" output.error = e.message;\n" +
"}\n" +
"\n" +
"output;",
)
probe.insert()
Custom Sensor
// Create custom sensor (ES5 ONLY!)
// Sensors run on ServiceNow instance to process probe results
// Table: discovery_sensors_script
var sensor = new GlideRecord("discovery_sensors_script")
sensor.initialize()
sensor.setValue("name", "Process Custom Application Version")
sensor.setValue("active", true)
sensor.setValue("probe", probeSysId)
// Sensor script (runs on instance - ES5 ONLY!)
sensor.setValue(
"script",
"(function process(result, source) {\n" +
" var output = JSON.parse(result.output);\n" +
" \n" +
" if (!output.success) {\n" +
' gs.warn("Custom app discovery failed: " + output.error);\n' +
" return;\n" +
" }\n" +
" \n" +
" // Find or create CI\n" +
" var ci = source.getDeviceRecord();\n" +
" if (ci) {\n" +
" ci.u_custom_app_version = output.app_version;\n" +
" ci.update();\n" +
' gs.info("Updated CI with app version: " + output.app_version);\n' +
" }\n" +
"})(result, source);",
)
sensor.insert()
Identification Rules (ES5)
CI Identification Rule
// Create identification rule (ES5 ONLY!)
var rule = new GlideRecord("cmdb_identifier")
rule.initialize()
rule.setValue("name", "Server Identification")
rule.setValue("table", "cmdb_ci_server")
rule.setValue("active", true)
// Priority (lower = higher priority)
rule.setValue("order", 100)
// Identification entries (criteria)
rule.insert()
// Add identification criteria
var entry = new GlideRecord("cmdb_identifier_entry")
entry.initialize()
entry.setValue("identifier", rule.getUniqueValue())
entry.setValue("criterion_attributes", "serial_number") // Match by serial
entry.setValue("search_type", "equals")
entry.setValue("active", true)
entry.insert()
Custom Identification Script
// Identification script for complex matching (ES5 ONLY!)
// Table: cmdb_identifier_script
var script = new GlideRecord("cmdb_identifier_script")
script.initialize()
script.setValue("name", "Custom Server Match")
script.setValue("table", "cmdb_ci_server")
script.setValue("active", true)
script.setValue(
"script",
"(function identify(source) {\n" +
' var serial = source.getValue("serial_number");\n' +
' var hostname = source.getValue("name");\n' +
" \n" +
" // Try serial match first\n" +
' var gr = new GlideRecord("cmdb_ci_server");\n' +
" if (serial) {\n" +
' gr.addQuery("serial_number", serial);\n' +
" gr.query();\n" +
" if (gr.next()) {\n" +
" return gr.getUniqueValue();\n" +
" }\n" +
" }\n" +
" \n" +
" // Try hostname + IP match\n" +
' gr = new GlideRecord("cmdb_ci_server");\n' +
' gr.addQuery("name", hostname);\n' +
' gr.addQuery("ip_address", source.getValue("ip_address"));\n' +
" gr.query();\n" +
" if (gr.next()) {\n" +
" return gr.getUniqueValue();\n" +
" }\n" +
" \n" +
" // No match - return null to create new CI\n" +
" return null;\n" +
"})(source);",
)
script.insert()
Discovery Status (ES5)
Monitor Discovery Status
// Check discovery run status (ES5 ONLY!)
function getDiscoveryStatus(scheduleSysId) {
var status = new GlideRecord("discovery_status")
status.addQuery("dscheduler", scheduleSysId)
status.orderByDesc("sys_created_on")
status.setLimit(1)
status.query()
if (status.next()) {
return {
state: status.state.getDisplayValue(),
started: status.getValue("started"),
completed: status.getValue("completed"),
devices_found: status.getValue("devices_found"),
devices_completed: status.getValue("devices_completed"),
errors: status.getValue("error_count"),
}
}
return null
}
Discovery Device Results
// Get discovered devices from a run (ES5 ONLY!)
function getDiscoveredDevices(statusSysId) {
var devices = []
var device = new GlideRecord("discovery_device_history")
device.addQuery("status", statusSysId)
device.query()
while (device.next()) {
devices.push({
ip_address: device.getValue("source"),
ci: device.cmdb_ci.getDisplayValue(),
ci_class: device.getValue("ci_type"),
state: device.state.getDisplayValue(),
issues: device.getValue("issue_count"),
})
}
return devices
}
MCP Tool Integration
Available Tools
| Tool | Purpose |
|---|
snow_query_table | Query discovery tables |
snow_find_artifact | Find discovery configs |
snow_execute_script_with_output | Test discovery scripts |
snow_cmdb_search | Search discovered CIs |
Example Workflow
// 1. Query active schedules
await snow_query_table({
table: "discovery_schedule",
query: "active=true",
fields: "name,discover,run_type,mid_server",
})
// 2. Check recent discovery status
await snow_execute_script_with_output({
script: `
var status = getDiscoveryStatus('schedule_sys_id');
gs.info(JSON.stringify(status));
`,
})
// 3. Find discovery errors
await snow_query_table({
table: "discovery_log",
query: "level=error^sys_created_on>=javascript:gs.daysAgo(1)",
fields: "message,source,sys_created_on",
})
Best Practices
- Credential Security - Use credential vault
- Schedule Off-Peak - Minimize network impact
- Range Management - Organize by network segment
- MID Server - Proper placement and sizing
- Identification - Clear matching criteria
- Reconciliation - Regular CMDB validation
- Monitoring - Track discovery health
- ES5 Only - No modern JavaScript syntax
