Managing Jenkins

Jenkins CI/CD Management Skill

Manage and monitor Jenkins CI/CD pipelines, agents, and builds.

Core Helper Functions

#!/bin/bash

# Jenkins REST API helper
jenkins_api() {
    local method="${1:-GET}"
    local endpoint="$2"
    local data="${3:-}"

    if [ -n "$data" ]; then
        curl -s -X "$method" \
            -u "${JENKINS_USER}:${JENKINS_API_TOKEN}" \
            -H "Content-Type: application/json" \
            "${JENKINS_URL}/${endpoint}" \
            -d "$data"
    else
        curl -s -X "$method" \
            -u "${JENKINS_USER}:${JENKINS_API_TOKEN}" \
            "${JENKINS_URL}/${endpoint}"
    fi
}

# Fetch JSON API for any Jenkins object
jenkins_json() {
    jenkins_api GET "${1}/api/json?${2:-}"
}

MANDATORY: Discovery-First Pattern

Always discover jobs, nodes, and queues before querying specific resources.

Phase 1: Discovery

#!/bin/bash

echo "=== Jenkins Server Info ==="
jenkins_json "" | jq '{version: .description, mode: .mode, useSecurity: .useSecurity}'

echo ""
echo "=== Job Summary ==="
jenkins_json "" "tree=jobs[name,color,lastBuild[number,result,timestamp]]" | jq -r '
    .jobs[] | "\(.name)\t\(.color)\t#\(.lastBuild.number // "none")\t\(.lastBuild.result // "running")"
' | column -t | head -30

echo ""
echo "=== Node Summary ==="
jenkins_json "computer" "tree=computer[displayName,offline,numExecutors]" | jq -r '
    .computer[] | "\(.displayName)\t\(if .offline then "OFFLINE" else "ONLINE" end)\texecutors=\(.numExecutors)"
' | column -t

echo ""
echo "=== Build Queue ==="
jenkins_json "queue" | jq -r '.items[] | "\(.task.name)\tqueued=\(.inQueueSince | . / 1000 | strftime("%H:%M:%S"))\treason=\(.why // "unknown")"' | head -10

Output Rules

• TOKEN EFFICIENCY: Target 50 lines per output
• Use tree= query parameter to limit API response fields
• Never dump full build logs — extract last 50 lines or relevant sections

Common Operations

Pipeline Status Dashboard

#!/bin/bash
echo "=== Pipeline Health Summary ==="
jenkins_json "" "tree=jobs[name,color,healthReport[score,description],lastBuild[number,result,duration]]" | jq '
    .jobs | {
        total: length,
        passing: [.[] | select(.color == "blue")] | length,
        failing: [.[] | select(.color == "red")] | length,
        unstable: [.[] | select(.color == "yellow")] | length,
        disabled: [.[] | select(.color == "disabled")] | length
    }'

echo ""
echo "=== Failing Jobs ==="
jenkins_json "" "tree=jobs[name,lastBuild[number,result,timestamp,duration]]" | jq -r '
    .jobs[] | select(.lastBuild.result == "FAILURE") |
    "\(.name)\t#\(.lastBuild.number)\t\(.lastBuild.timestamp / 1000 | strftime("%Y-%m-%d %H:%M"))\tduration=\(.lastBuild.duration / 1000 | floor)s"
' | column -t

Build Analysis

#!/bin/bash
JOB_NAME="${1:?Job name required}"

echo "=== Recent Builds: $JOB_NAME ==="
jenkins_json "job/${JOB_NAME}" "tree=builds[number,result,timestamp,duration,changeSets[items[author[fullName],msg]]]{0,10}" | jq -r '
    .builds[] |
    "\(#\(.number))\t\(.result // "RUNNING")\t\(.timestamp / 1000 | strftime("%Y-%m-%d %H:%M"))\t\(.duration / 1000 | floor)s"
' | column -t

echo ""
echo "=== Last Failed Build Console (tail) ==="
LAST_FAIL=$(jenkins_json "job/${JOB_NAME}/lastFailedBuild" "tree=number" | jq '.number')
if [ "$LAST_FAIL" != "null" ]; then
    jenkins_api GET "job/${JOB_NAME}/${LAST_FAIL}/consoleText" | tail -50
fi

Agent Health Monitoring

#!/bin/bash
echo "=== Agent Details ==="
jenkins_json "computer" "tree=computer[displayName,offline,offlineCauseReason,temporarilyOffline,monitorData[*]]" | jq -r '
    .computer[] |
    "\(.displayName)\t\(if .offline then "OFFLINE" else "ONLINE" end)\t\(.offlineCauseReason // "none")"
' | column -t

echo ""
echo "=== Agent Disk Space ==="
jenkins_json "computer" | jq -r '
    .computer[] |
    select(.monitorData["hudson.node_monitors.DiskSpaceMonitor"] != null) |
    "\(.displayName)\t\(.monitorData["hudson.node_monitors.DiskSpaceMonitor"].size / 1073741824 | floor)GB free"
' | column -t

echo ""
echo "=== Offline Agents ==="
jenkins_json "computer" | jq -r '
    .computer[] | select(.offline == true) |
    "\(.displayName)\ttemporary=\(.temporarilyOffline)\treason=\(.offlineCauseReason // "unknown")"
' | column -t

Plugin Management

#!/bin/bash
echo "=== Installed Plugins ==="
jenkins_json "pluginManager" "tree=plugins[shortName,version,active,hasUpdate,longName]&depth=1" | jq -r '
    .plugins[] | "\(.shortName)\tv\(.version)\t\(if .active then "ACTIVE" else "INACTIVE" end)\t\(if .hasUpdate then "UPDATE_AVAILABLE" else "current" end)"
' | sort | column -t

echo ""
echo "=== Plugins With Updates ==="
jenkins_json "pluginManager" "tree=plugins[shortName,version,hasUpdate]&depth=1" | jq -r '
    .plugins[] | select(.hasUpdate == true) | "\(.shortName)\tv\(.version)"
' | column -t

Credential Audit

#!/bin/bash
echo "=== Credential Domains ==="
jenkins_api GET "credentials/store/system/domain/_/api/json?tree=credentials[id,typeName,displayName,description]" | jq -r '
    .credentials[] | "\(.id)\t\(.typeName)\t\(.displayName // .description // "unnamed")"
' | column -t

echo ""
echo "=== Credential Usage ==="
echo "NOTE: Jenkins does not expose credential values via API — only metadata is shown."

Anti-Hallucination Rules

• NEVER guess Jenkins job names — always discover via API first
• NEVER fabricate build numbers — query the job for actual build history
• NEVER assume folder structure — Jenkins supports nested folders (use job/folder/job/name paths)
• API responses vary by installed plugins — check before assuming fields exist

Safety Rules

• NEVER trigger builds without explicit user confirmation
• NEVER delete jobs or builds without user approval
• NEVER expose credential values — Jenkins API only returns metadata, never secrets
• Use tree= parameter to limit data fetched — avoid overloading the controller

Output Format

Present results as a structured report:

Managing Jenkins Report
═══════════════════════
Resources discovered: [count]

Resource       Status    Key Metric    Issues
──────────────────────────────────────────────
[name]         [ok/warn] [value]       [findings]

Summary: [total] resources | [ok] healthy | [warn] warnings | [crit] critical
Action Items: [list of prioritized findings]

Target ≤50 lines of output. Use tables for multi-resource comparisons.

Counter-Rationalizations

Common Pitfalls

• Crumbs (CSRF): Jenkins requires a crumb for POST requests — fetch via /crumbIssuer/api/json first
• Folder paths: Jobs inside folders use job/folder-name/job/job-name URL encoding
• Blue/Red/Yellow: blue = success, red = failure, yellow = unstable, blue_anime = building
• API depth: Some nested data requires depth=1 or depth=2 query parameter
• Rate limits: Jenkins has no built-in rate limiting, but heavy API use can overload the controller
• Pipeline vs Freestyle: Pipeline jobs have different API structure than freestyle — check job type first