blog.healthchecks.ioHealthchecks.io – The Joy of Building a Cron Monitoring Service

OnCalendar schedules: Monitor Systemd Timers with Healthchecks.io By Pēteris Caune / December 18, 2023 May 1, 2024 Healthchecks now supports OnCalendar schedules, used for scheduling tasks with systemd timers . Here’s what’s new: when creating a check, you can now switch between Simple”, Cron” and OnCalendar” schedules: You can also edit schedules (and switch schedule types) for existing checks: The UI control for entering the schedule is a multi-line textbox, and yes, you can specify multiple schedules there – Healthchecks will expect a ping when any schedule matches: Note: the schedule field is currently limited to 100 characters. You will be able to enter 2-3 schedules, but probably not 10+ schedules. systemd allows you to specify a timezone inside the OnCalendar expression. So does Healthchecks: The API now supports OnCalendar schedules as well. You can pass either cron schedule or OnCalendar expression(s) in the schedule” field for the Create a new check and Update an existing check calls, and Healthchecks will detect the schedule type automatically: $ curl -s https://healthchecks.io/api/v3/checks/ \ header "X-Api-Key: fdYYw32ftDvYQoCe4C1JUgp7SlPbOYTI" \ data ’{"name": "Runs at 8AM", "schedule": "8:00"}’ | jq . { "name": "Runs at 8AM", "slug": "", "tags": "", "desc": "", "grace": 3600, "n_pings": 0, "status": "new", "started": false, "last_ping": null, "next_ping": null, "manual_resume": false, "methods": "", "subject": "", "subject_fail": "", "start_kw": "", "success_kw": "", "failure_kw": "", "filter_subject": false, "filter_body": false, "ping_url": "https://hc-ping.com/97f70e1c-bf2b-4244-ba44-de413c93fab4", "update_url": "https://healthchecks.io/api/v3/checks/97f70e1c-bf2b-4244-ba44-de413c93fab4", "pause_url": "https://healthchecks.io/api/v3/checks/97f70e1c-bf2b-4244-ba44-de413c93fab4/pause", "resume_url": "https://healthchecks.io/api/v3/checks/97f70e1c-bf2b-4244-ba44-de413c93fab4/resume", "channels": "", "schedule": "8:00", "tz": "UTC" } Under the hood, the OnCalendar schedule parsing logic is implemented in a separate oncalendar” library . Feel free to use it in your own Python projects as well! The OnCalendar schedule support is live on https://healthchecks.io and available to all accounts. Happy monitoring! –Pēteris Comparison of Cron Monitoring Services (November 2023) By Pēteris Caune / November 23, 2023 January 19, 2024 In this post I’m comparing cron monitoring features of four services: Cronitor , Healthchecks.io , Uptime Robot , Sentry . How I picked the services for comparison: I searched for cron monitoring” on Google and picked the top results in their order of appearance. Disclaimer: I run Healthchecks.io, so I’m a biased source. I’ve tried to get the facts right, but choosing what features to compare, and what differences to highlight, is of course subjective. When in doubt, do your own research! Business Stats Cronitor launched in 2014, is registered in the United States and runs on AWS. Cronitor is a bootstrapped company, and is operated by three friendly humans . Cronitor started as a cron monitoring service, but has expanded to website uptime monitoring, real user monitoring, and hosted status pages. Cronitor is a proprietary product and uses the SaaS business model. Healthchecks.io launched in 2015, is registered in Latvia and runs on Hetzner (Germany). Healthchecks.io is a bootstrapped company, run by a solo founder. Healthchecks.io focuses on doing one thing and doing it well: alerting when something does not happen on time . Healthchecks.io is open source ( source on GitHub ), users can use the hosted service, or run a self-hosted instance. Uptime Robot launched in 2010, is registered in Malta, and runs on Limestone Networks, AWS, and DigitalOcean. UptimeRobot started as a free website uptime monitoring service and added cron monitoring and hosted status pages support in 2019. After getting acquired in late 2019, UptimeRobot accelerated development and reorganized its pricing structure. Uptime Robot is a proprietary product and uses the SaaS business model. Sentry launched in 2012, is registered in the United States and runs on AWS and Google Cloud. Sentry is a VC-funded company and has 200+ employees. Sentry started as an error tracking service, grew into APM, and launched cron monitoring support in public beta in January 2023. Sentry uses the SaaS business model, but its source code is available under the FSL license . Sentry is a complex product with many moving parts. Self-hosting is possible but is not trivial. Pricing Each reviewed service except Healthchecks.io bundles several products under one account: Cronitor: cron monitoring , website uptime monitoring, RUM, status pages. Uptime Robot: website uptime monitoring , cron monitoring, status pages. Sentry: error tracking , APM, code coverage. The total set of functionality you get from a paid account on each service is vastly different, so their pricing is not directly comparable. With that in mind, here is the pricing summary for each service, as of November 2023, for monitoring cron jobs specifically. Cronitor Free plan: monitor up to 5 jobs. Business plan: $2/mo for 1 job. Monitoring 100 jobs with Cronitor would cost $200/mo. Healthchecks.io Free plan: monitor up to 20 jobs. Business plan: $20/mo for 100 jobs. Business Plus plan: $80/mo for 1000 jobs. Monitoring 100 jobs with Healthchecks.io would cost $20/mo. Healthchecks.io offers sponsored accounts for non-profits and open-source projects ( details ). Uptime Robot Solo plan: $8/mo for 10 jobs or $19/mo for 50 jobs. Team plan: $34/mo for 100 jobs. Enterprise plan: $64/mo for 200 jobs. Monitoring 100 jobs with Uptime Robot would cost $34/mo. Uptime Robot offers sponsored accounts for charities and other non-profits ( details ). Sentry Sentry Cron Monitoring feature is currently in open beta. The limits for different pricing plans are not known yet. Sentry announced general availability and pricing in January 16, 2024. Free: monitor 1 cron job for free. Paid: $0.78/mo for 1 job. Monitoring 100 jobs with Sentry would cost $77/mo. Sentry offers sponsored accounts for non-profits, open-source, and students ( details ). Timeout-based Schedules When using timeout-based schedules the user specifies a period (for example, one hour). The monitored system is expected to check in” (send an HTTP request to a unique address) at least every period. When a check-in is missed, the monitoring system declares an outage and notifies you. This monitoring technique is also sometimes called Heartbeat Monitoring . All four reviewed services support timeout-based schedules. Cron Expression Schedules The user specifies a cron expression (for example, 0/5 * * * *”) and a timezone. The monitoring system calculates expected check in” deadlines based on the cron expression. Supported by: Cronitor, Healthchecks.io, Sentry. Not supported by: Uptime Robot. Cronitor and Sentry use the croniter library to evaluate cron expressions. Healthchecks.io uses the cronsim library. Start and Fail Signals In addition to basic I’m alive!” check-in messages, monitoring services typically support additional signal types: job started” signal: allows the measurement of job durations, and alerting when a job takes too long. job failed” signal: allows the job to explicitly declare itself as failed. Supported by: Cronitor ( docs ), Healthchecks.io ( docs ), Sentry ( docs ). Not supported by: Uptime Robot. Check-in Via Email With this feature, clients can check in” by sending an email message to a job-specific email address. This comes in handy when integrating with services that only support status reports via emails, or when working in restrictive environments where only email is allowed through. Supported by: Cronitor ( docs ), Healthchecks.io ( docs ). Not supported by: Uptime Robot, Sentry. Auto-Provisioning With auto-provisioning clients can perform check-ins for jobs that the monitoring system does not yet know about, and the monitoring service...