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