yacron2 1.2.1

A modern, distributed, fault-tolerant, highly available, leader-electing, container-friendly, highly configurable, precompiled, multi-architecture, portable, security-hardened, production-ready cron replacement.

yacron2 (Yet Another Cron ...2)

A modern, optionally-distributed, fault-tolerant, highly available, leader-electing, container-friendly, highly configurable, precompiled, multi-architecture, portable, security-hardened, production-ready cron replacement.

yacron2 is a fork of yacron (by Gustavo Carneiro), continuing development from version 0.19.

Features

• "Crontab" is in YAML format; classic crontab files are accepted as-is too (see Classic crontab files)
• Builtin sending of Sentry and Mail outputs when cron jobs fail
• Flexible configuration: you decide how to determine if a cron job fails or not
• Designed for running in Docker, Kubernetes, or 12 factor environments:
  • Runs in the foreground
  • Logs everything to stdout/stderr
  • Production-ready for locked-down corporate container platforms: runs as a non-root user, under a restricted seccomp profile, with a read-only root filesystem, an fsGroup-mounted config, and all Linux capabilities dropped, so no writable paths or elevated privileges are required (see Production container deployment)
• Option to automatically retry failing cron jobs, with exponential backoff
• Optional HTTP REST API, to fetch status, start jobs, cancel running jobs, and read per-job run history on demand
• Native Prometheus metrics at /metrics (plus per-job statsd push metrics), covering run outcomes, durations, retries, schedules, and cluster health (see Metrics)
• A job-set id: an order-independent fingerprint of every job's effective configuration, so replicas deployed from the same config can confirm they hold an identical set of jobs (see Job-set id)
• Opt-in clustering and leader election: optionally have instances confirm over mutual TLS that a configured set of peers is running the same job set, and elect a leader so several replicas can run from one config without double-running jobs (see Clustering and leader election)
• Arbitrary timezone support
• Optional live control panel to watch every job's status, tail its logs in real time, run or cancel jobs on demand, and review run history, success rates, and schedules

Installation

Run with Docker

Prebuilt, multi-architecture (linux/amd64, linux/arm64, linux/386, linux/arm/v7, linux/ppc64le, linux/s390x and linux/riscv64) images are published on every release to two registries: the GitHub Container Registry and Docker Hub. The images are identical; pull from whichever you prefer. The default image is built on Debian (slim); if you would rather match a particular base, Alpine, Ubuntu, RHEL/UBI and other variants are published from the same release too. Mount your crontab and go:

# GitHub Container Registry
docker run --rm \
  -v "$PWD/yacron2tab.yaml:/etc/yacron2.d/yacron2tab.yaml:ro" \
  ghcr.io/ptweezy/yacron2:latest

# Docker Hub
docker run --rm \
  -v "$PWD/yacron2tab.yaml:/etc/yacron2.d/yacron2tab.yaml:ro" \
  ptweezy/yacron2:latest

The image runs as a non-root user and reads its configuration from /etc/yacron2.d by default. For production, pin a specific version instead of latest (e.g. ghcr.io/ptweezy/yacron2:1.0.14 or ptweezy/yacron2:1.0.14) and see Production container deployment for the hardened Kubernetes/Docker setup.

Distro variants

The default latest (and <version>) image is built on Debian (slim). The same release is also published on several other bases, so you can match a specific one to your environment: a familiar userland, an image-provenance policy that mandates a particular vendor, or the smallest possible image. Each variant adds a -<distro> suffix to the tag (and the default Debian image is also available explicitly as -debian):

Tag suffix	Base image	Python	Notes
(none) / -debian	python:3.14-slim	3.14	Default. Widest architecture coverage.
-alpine	python:3.14-alpine	3.14	musl libc; smallest image.
-ubuntu	ubuntu:24.04	3.12	Ubuntu LTS userland.
-rhel	UBI 9 (ubi-minimal)	3.12	Red Hat base for RHEL / OpenShift.
-fedora	fedora:41	3.13	Leading-edge RPM userland.
-opensuse	opensuse/leap:15.6	3.11	SUSE / SLES family.
-amazonlinux	amazonlinux:2023	3.11	AWS-centric deployments.
-distroless	gcr.io/distroless/python3	3.11	No shell or package manager; minimal attack surface.

# e.g. the Alpine variant, pinned to a version:
docker run --rm \
  -v "$PWD/yacron2tab.yaml:/etc/yacron2.d/yacron2tab.yaml:ro" \
  ghcr.io/ptweezy/yacron2:1.0.14-alpine

yacron2 is a pure-Python app that supports any Python >= 3.10, so behavior is identical across variants. Pick the base, not the interpreter version. The Debian default covers the most architectures; each variant covers the arches its base image publishes (Alpine matches Debian's full set; RHEL, Fedora, openSUSE and distroless cover amd64, arm64, ppc64le and s390x; Amazon Linux covers amd64 and arm64). All variants share the same non-root, read-only-friendly hardening as the default image.

Install using pip

yacron2 requires Python >= 3.10 (for systems with older Python, use the binary instead). It is advisable to install it in a Python virtual environment, for example:

python3 -m venv yacron2env
. yacron2env/bin/activate
pip install yacron2

Install using pipx

pipx automates creating a virtualenv and installing a python program in the newly created virtualenv. It is as simple as:

pipx install yacron2

Install using binary

Alternatively, a self-contained binary can be downloaded from github: https://github.com/ptweezy/yacron2/releases. Every release automatically attaches binaries for Linux (amd64, arm64, i686, armv7, armv6, ppc64le, s390x and riscv64), macOS (amd64 and arm64) and Windows (amd64 and arm64):

• Linux: glibc builds (yacron2-linux-<arch>) for the mainstream distros, working on any system post glibc 2.39 (e.g. Ubuntu 24.04) on the matching CPU, plus musl builds (yacron2-linux-<arch>-musl) for Alpine and other musl-based systems. <arch> is one of amd64, arm64, i686 (32-bit x86), armv7 (32-bit ARM, e.g. older Raspberry Pi), armv6 (musl only), ppc64le (POWER), s390x (IBM Z) or riscv64 (64-bit RISC-V).
• macOS: yacron2-macos-arm64 (Apple Silicon) / yacron2-macos-amd64 (Intel).
• Windows: yacron2-windows-amd64.exe (x64) / yacron2-windows-arm64.exe (ARM64).

Python is not required on the target system (it is embedded in the executable):

# pick the asset for your OS and architecture (glibc amd64 Linux shown; append
# -musl on Alpine, or use yacron2-macos-<arch> on a Mac)
curl -fsSL -o yacron2 \
  https://github.com/ptweezy/yacron2/releases/latest/download/yacron2-linux-amd64
chmod +x yacron2
./yacron2 --version

The macOS binaries are signed and notarized by Apple.

The standalone binary is a self-extracting executable: on each start it unpacks its embedded Python runtime into a temporary directory and loads shared libraries from there. It therefore needs a temporary directory that is both writable and executable. On an ordinary system the default /tmp already satisfies this, so no extra setup is required.

This only matters when you run the binary under a read-only root filesystem (for example, a hardened container). With the root filesystem read-only, /tmp is read-only too, and the binary aborts at startup: Could not create temporary directory, or Error loading shared library …: Operation not permitted. Give it a small writable and executable temp mount and it runs fine:

# Note `exec`: Docker's --tmpfs defaults to `noexec`, but the binary must be
# able to execute the libraries it unpacks.
docker run --rm --read-only \
  --tmpfs /tmp:rw,exec,nosuid,nodev,size=64m \
  -v "$PWD/yacron2tab.yaml:/etc/yacron2.d/yacron2tab.yaml:ro" \
  your-image-with-the-binary -c /etc/yacron2.d

On Kubernetes, mount an emptyDir at /tmp (an emptyDir is writable and executable by default; use medium: Memory for a tmpfs). Alternatively, point the binary at another writable, executable directory with TMPDIR=/path.

This requirement is unique to the standalone binary. The published container image (and pip/pipx installs) run yacron2 as a normal Python package with the interpreter on disk, so they never self-extract and need no writable temp directory. See Production container deployment.

Running on Windows

yacron2 runs natively on Windows (x64 and ARM64), in addition to Linux and macOS. Install it with pip install yacron2, or download the self-contained yacron2-windows-amd64.exe / yacron2-windows-arm64.exe from the releases page (no Python required). Everything else, like the YAML crontab, scheduling, reporting, retries, the HTTP API and the web dashboard, works the same as on POSIX. A few platform details differ:

• Default config location. When -c is omitted, yacron2 looks in %APPDATA%\yacron2 (e.g. C:\Users\you\AppData\Roaming\yacron2), the Windows analog of /etc/yacron2.d. Point it anywhere with -c:

  yacron2 -c C:\path\to\yacron2tab.yaml
  

• Default shell. A string command with no explicit shell runs through the native command processor (%ComSpec%, i.e. cmd.exe), mirroring the /bin/sh default on POSIX. For PowerShell, or any other interpreter, set shell: or pass command as a list (which bypasses the shell entirely):

  jobs:
    - name: powershell-job
      command:
        - powershell
        - -Command
        - Get-Date
      schedule: "*/5 * * * *"
      captureStdout: true
  

• Graceful shutdown. Press Ctrl-C (or Ctrl-Break) to stop yacron2; it shuts down after the currently running jobs finish, just as SIGTERM does on POSIX.

• Not supported on Windows. Per-job user/group switching (there is no setuid/setgid equivalent) is rejected with a clear configuration error, and unix:// web listeners are skipped with a warning. Use an http:// listener instead.

Production container deployment

yacron2 is built to run unmodified under the hardened security contexts that corporate and enterprise Kubernetes / container platforms enforce. At runtime the daemon only reads its configuration and secrets and writes its output to stdout/stderr. It never needs a writable working directory, temp files, or log files, so it slots cleanly into a locked-down pod:

• Non-root user: yacron2 needs no special privileges to run, so the whole daemon can run as an unprivileged UID. Only the optional per-job user/group switching (see Change to another user/group) requires running as root; if you don't use that feature, drop root entirely.
• Seccomp profile: yacron2 makes no exotic syscalls, so the RuntimeDefault seccomp profile (or an equivalently strict custom profile) works out of the box.
• Read-only root filesystem: no runtime writes are required by the published image (or a pip/pipx install). Mount your crontab config read-only. (If you enable the optional HTTP interface on a Unix socket, point the socket at a small writable emptyDir volume rather than the root filesystem. And if you deploy the standalone binary instead of the image, it additionally needs a small writable, executable temp mount; see Install using binary.)
• fsGroup and dropped capabilities: config and secret volumes can be mounted with an fsGroup so the non-root process can read them, and you can drop all Linux capabilities and forbid privilege escalation.

The published image (ghcr.io/ptweezy/yacron2 and docker.io/ptweezy/yacron2) is already built this way (non-root, with yacron2 -c /etc/yacron2.d as its entrypoint and no writable paths required), so for most deployments you can use it directly and mount your crontab read-only. If you would rather bake the configuration into your own image, base it on the published image:

FROM ghcr.io/ptweezy/yacron2:latest

# The base image already runs as the non-root user 65534.
COPY yacron2tab.yaml /etc/yacron2.d/yacron2tab.yaml

And a corresponding Kubernetes Deployment with a fully restricted security context:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: yacron2
spec:
  replicas: 1
  selector:
    matchLabels:
      app: yacron2
  template:
    metadata:
      labels:
        app: yacron2
    spec:
      securityContext:           # pod-level
        runAsNonRoot: true
        runAsUser: 65534
        runAsGroup: 65534
        fsGroup: 65534           # lets the non-root process read mounted volumes
        seccompProfile:
          type: RuntimeDefault
      containers:
        - name: yacron2
          image: ghcr.io/ptweezy/yacron2:latest
          args: ["-c", "/etc/yacron2.d"]
          securityContext:       # container-level
            allowPrivilegeEscalation: false
            readOnlyRootFilesystem: true
            capabilities:
              drop:
                - ALL
          resources:
            limits:
              cpu: 200m
              memory: 128Mi
            requests:
              cpu: 10m
              memory: 64Mi
          volumeMounts:
            - name: crontab
              mountPath: /etc/yacron2.d
              readOnly: true
      volumes:
        - name: crontab
          configMap:
            name: yacron2tab

Web dashboard

yacron2 ships with a built-in web dashboard. Point your browser at the HTTP listener and you have a keyboard-driven control room for every job.

The overview shows every job with its live status, a countdown to its next run, how long the last run took, an exit-code badge, and a sparkline of recent runs, all sortable, filterable, and searchable. Click any job (or press Enter) to open its detail drawer:

Live log tail	Run history	Schedule, explained
Follow a running job's output live over Server-Sent Events, with ANSI color, in-log grep (plain text or regex), per-line timestamps, line-wrap, and one-click download.	Success rate plus average / min / max duration over the retained history, with a color-coded per-run duration chart and the full run log.	A plain-English reading of the cron expression and a timezone-aware preview of the next run times, computed live in the browser.

Everything is one keypress away: a fuzzy command palette (Ctrl-K / ⌘K) runs any action or jumps to any job, ? lists every shortcut, / filters, j/k move the cursor, r runs the selected job and x cancels it. You can run a single job, or every failing job at once, on demand, with a click.

Fuzzy command palette	Keyboard-first, with a shortcut for everything

Three built-in themes (amber and green phosphor CRT, or a flat modern look), plus configurable CRT glow, scanlines, compact density, desktop failure notifications, and polling interval, all remembered in your browser (and the CRT effects honor prefers-reduced-motion):

Green phosphor CRT	Flat modern theme

Run history and live logs are kept in memory only, and the page is served with a strict Content-Security-Policy. Turn it on with a one-line web: block: the web dashboard tour in the wiki is the full walkthrough, and Remote web/HTTP interface below shows how to enable it.

Try it: docker compose -f docker-compose-zen.yml up boots a single node with a demo job set, and docker compose -f docker-compose-cluster.yml up boots a 3-node cluster (yacron-a/yacron-b/yacron-c) so you can open each node's dashboard and watch the cluster panel and leader election live.

Usage

Configuration is in YAML format. To start yacron2, give it a configuration file or directory path as the -c argument. For example:

yacron2 -c /tmp/my-crontab.yaml

This starts yacron2 (always in the foreground!), reading /tmp/my-crontab.yaml as configuration file. If the path is a directory, any *.yaml or *.yml files inside this directory are taken as configuration files, along with any classic crontabs (*.crontab, *.cron, or a file named crontab; see Classic crontab files).

Configuration basics

This configuration runs a command every 5 minutes:

jobs:
  - name: test-01
    command: echo "foobar"
    shell: /bin/bash
    schedule: "*/5 * * * *"

The command can be a string or a list of strings. If command is a string, yacron2 runs it through a shell, which is /bin/bash in the above example, but is /bin/sh by default.

If the command is a list of strings, the command is executed directly, without a shell. The ARGV of the command to execute is extracted directly from the configuration:

jobs:
  - name: test-01
    command:
      - echo
      - foobar
    schedule: "*/5 * * * *"

The schedule option can be a string in a crontab format specified by https://github.com/josiahcarlson/parse-crontab (this module is used by yacron2). Additionally @reboot can be included , which will only run the job when yacron2 is initially executed. Further schedule can be an object with properties. The following configuration runs a command every 5 minutes, but only on the specific date 2017-07-19, and doesn't run it in any other date:

jobs:
  - name: test-01
    command: echo "foobar"
    schedule:
      minute: "*/5"
      dayOfMonth: 19
      month: 7
      year: 2017
      dayOfWeek: "*"

Important: by default all time is interpreted to be in UTC, but you can request to use local time instead. For instance, the cron job below runs every day at 19h27 local time because of the utc: false option:

jobs:
  - name: test-01
    command: echo "hello"
    schedule: "27 19 * * *"
    utc: false
    captureStdout: true

You can also request that the schedule be interpreted in an arbitrary timezone, using the timezone attribute:

jobs:
  - name: test-01
    command: echo "hello"
    schedule: "27 19 * * *"
    timezone: America/Los_Angeles
    captureStdout: true

You can ask for environment variables to be defined for command execution:

jobs:
  - name: test-01
    command: echo "foobar"
    shell: /bin/bash
    schedule: "*/5 * * * *"
    environment:
      - key: PATH
        value: /bin:/usr/bin

You can also provide an environment file to define environments for command execution:

jobs:
  - name: test-01
    command: echo "foobar"
    shell: /bin/bash
    schedule: "*/5 * * * *"
    env_file: .env

The env file must be a list of KEY=VALUE pairs. Empty lines and lines starting with # will be ignored.

Variables declared in the environment option will override those found in the env_file.

Classic crontab files

Already have a crontab? yacron2 runs it as-is. A file named *.crontab, *.cron, or just crontab (so -c /etc/crontab works) is read in the classic Vixie format, whether passed directly to -c, dropped into a config directory next to YAML files, or pulled in with include::

SHELL=/bin/bash
PATH=/usr/local/bin:/usr/bin:/bin

# m h dom mon dow command
*/15 * * * *  /usr/local/bin/backup --incremental
30 4 * * mon-fri  /usr/local/bin/report --daily
@daily  /usr/local/bin/rotate-logs
0 0 * * *  pg_dump mydb > /backup/mydb-$(date +\%F).sql

Comments, NAME=value environment lines (position-sensitive, SHELL and CRON_TZ honored), the @reboot/@daily/... nicknames, and \% escapes all work as in man 5 crontab. Each entry becomes an ordinary yacron2 job named <file>:<line>, configured to yacron2's standard defaults rather than an emulation of cron's environment: schedules run in UTC unless the crontab sets CRON_TZ, failure means a non-zero exit or stderr output (no MAILTO mail), and the %-as-stdin feature is a load-time error instead of a silent surprise (\% still gives a literal %). When an entry needs retries, reporting, timeouts, or any other per-job option, move it to YAML. The full mapping and every deviation are documented in the Classic Crontabs wiki page, and a runnable example (a config directory mixing a crontab with YAML and the dashboard) lives in example/crontab.

Specifying defaults

There can be a special defaults section in the config. Any attributes defined in this section provide default values for cron jobs to inherit. Although cron jobs can still override the defaults, as needed:

defaults:
    environment:
      - key: PATH
        value: /bin:/usr/bin
    shell: /bin/bash
    utc: false
jobs:
  - name: test-01
    command: echo "foobar"  # runs with /bin/bash as shell
    schedule: "*/5 * * * *"
  - name: test-02  # runs with /bin/sh as shell
    command: echo "zbr"
    shell: /bin/sh
    schedule: "*/5 * * * *"

Note: if the configuration option is a directory and there are multiple configuration files in that directory, then the defaults section in each configuration file provides default options only for cron jobs inside that same file; the defaults have no effect beyond any individual YAML file.

Reporting

Yacron2 has builtin support for reporting jobs failure (more on that below) by email, Sentry and shell command (additional reporting methods might be added in the future):

- name: test-01
  command: |
    echo "hello" 1>&2
    sleep 1
    exit 10
  schedule:
    minute: "*/2"
  captureStderr: true
  onFailure:
    report:
      sentry:
        dsn:
          value: example
          # Alternatively:
          # fromFile: /etc/secrets/my-secret-dsn
          # fromEnvVar: SENTRY_DSN
        fingerprint:  # optional
          - yacron2
          - "{{ environment.HOSTNAME }}"
          - "{{ name }}"
        extra:
          foo: bar
          zbr: 123
        level: warning
        environment: production
      mail:
        from: [e-mail]
        to: [e-mail]
        smtpHost: 127.0.0.1
        # optional fields:
        username: "username1"  # set username and password to enable login
        password:
          value: example
          # Alternatively:
          # fromFile: /etc/secrets/my-secret-password
          # fromEnvVar: MAIL_PASSWORD
        tls: false  # set to true to enable TLS
        starttls: false  # set to true to enable StartTLS
      shell:
        shell: /bin/bash
        command: ...

Here, the onFailure object indicates that what to do when a job failure is detected. In this case we ask for it to be reported both to sentry and by sending an email.

The captureStderr: true part instructs yacron2 to capture output from the the program's standard error, so that it can be included in the report. We could also turn on standard output capturing via the captureStdout: true option. By default, yacron2 captures only standard error. If a cron job's standard error or standard output capturing is not enabled, these streams will simply write to the same standard output and standard error as yacron2 itself.

Both stdout and stderr stream lines are by default prefixed with [{job_name} {stream_name}], i.e. [test-01 stdout], if for any reason you need to change this, provide the option streamPrefix with your own custom string.

- name: test-01
  command: echo "hello world"
  schedule:
    minute: "*/2"
  captureStdout: true
  streamPrefix: "[{job_name} job]"

In some cases, for instance when you're logging JSON objects you might want to completely get rid of the prefix altogether:

- name: test-01
  command: echo "hello world"
  schedule:
    minute: "*/2"
  captureStdout: true
  streamPrefix: ""

It is possible also to report job success, as well as failure, via the onSuccess option.

- name: test-01
  command: echo "hello world"
  schedule:
    minute: "*/2"
  captureStdout: true
  onSuccess:
    report:
      mail:
        from: [e-mail]
        to: [e-mail]
        smtpHost: 127.0.0.1

It is possible to customize the format of the report. For mail reporting, the option subject indicates what is the subject of the email, while body formats the email body. For Sentry reporting, there is only body. In all cases, the values of those options are strings that are processed by the jinja2 templating engine. The following variables are available in templating:

• name(str): name of the cron job
• success(bool): whether or not the cron job succeeded
• stdout(str): standard output of the process
• stderr(str): standard error of the process
• exit_code(int): process exit code
• command(str): cron job command
• shell(str): cron job shell
• environment(dict): subprocess environment variables

Example:

- name: test-01
  command: |
    echo "hello" 1>&2
    sleep 1
    exit 10
  schedule:
    minute: "*/2"
  captureStderr: true
  onFailure:
    report:
      mail:
        from: [e-mail]
        to: [e-mail]
        smtpHost: 127.0.0.1
        subject: Cron job '{{name}}' {% if success %}completed{% else %}failed{% endif %}
        body: |
          {{stderr}}
          (exit code: {{exit_code}})

The shell reporter executes a user given shell command in the specified shell. It passes all environment variables from the python executable and specifies some additional ones to inform about the state of the job:

• YACRON2_FAIL_REASON (str)
• YACRON2_FAILED ("1" or "0")
• YACRON2_JOB_NAME (str)
• YACRON2_JOB_COMMAND (str)
• YACRON2_JOB_SCHEDULE (str)
• YACRON2_RETCODE (str)
• YACRON2_STDERR (str)
• YACRON2_STDOUT (str)

A simple example configuration:

- name: test-01
  command: echo "foobar" && exit 123
  shell: /bin/bash
  schedule: "* * * * *"
  onFailure:
    report:
      shell:
        shell: /bin/bash
        command: echo "Error code $YACRON2_RETCODE"

It is possible to send emails formatted as html, by adding the html: true property. For example, here the standard output of a shell command is captured and interpreted as html and placed in the email message:

- name: test-01
  command: echo "hello <b>world</b>"
  schedule: "@reboot"
  captureStdout: true
  onSuccess:
    report:
      mail:
        from: [e-mail]
        to: [e-mail], [e-mail]
        html: true
        smtpHost: 127.0.0.1
        smtpPort: 1025
        subject: This is a cron job with html body

Metrics

Yacron2 natively exposes Prometheus metrics whenever the HTTP REST API is enabled -- no exporter sidecar needed:

web:
  listen:
    - http://127.0.0.1:8080

GET /metrics then serves job run outcomes, duration histograms, retries, next-run times, config-reload health, and cluster/leader-election state, in both the Prometheus text format and OpenMetrics. See Metrics with Prometheus for the full metric reference, scrape configuration, and example alert rules.

Yacron2 also has builtin support for pushing per-job metrics to Statsd:

jobs:
  - name: test01
    command: echo "hello"
    schedule: "* * * * *"
    statsd:
      host: my-statsd.example.com
      port: 8125
      prefix: my.cron.jobs.prefix.test01

With this config Yacron2 will write the following metrics over UDP to the Statsd listening on my-statsd.example.com:8125:

my.cron.jobs.prefix.test01.start:1|g  # this one is sent when the job starts
my.cron.jobs.prefix.test01.stop:1|g   # the rest are sent when the job stops
my.cron.jobs.prefix.test01.success:1|g
my.cron.jobs.prefix.test01.duration:3|ms|@0.1

Handling failure

By default, yacron2 considers that a job has failed if either the process returns a non-zero code or if it generates output to standard error (and standard error capturing is enabled, of course).

You can instruct yacron2 how to determine if a job has failed or not via the failsWhen option:

failsWhen:
  producesStdout: false
  producesStderr: true
  nonzeroReturn: true
  always: false

producesStdout : If true, any captured standard output causes yacron2 to consider the job as failed. This is false by default.

producesStderr : If true, any captured standard error causes yacron2 to consider the job as failed. This is true by default.

nonzeroReturn : If true, if the job process returns a code other than zero causes yacron2 to consider the job as failed. This is true by default.

always : If true, if the job process exits that causes yacron2 to consider the job as failed. This is false by default.

It is possible to instruct yacron2 to retry failing cron jobs by adding a retry option inside onFailure:

- name: test-01
  command: |
    echo "hello" 1>&2
    sleep 1
    exit 10
  schedule:
    minute: "*/10"
  captureStderr: true
  onFailure:
    report:
      mail:
        from: [e-mail]
        to: [e-mail]
        smtpHost: 127.0.0.1
    retry:
      maximumRetries: 10
      initialDelay: 1
      maximumDelay: 30
      backoffMultiplier: 2

The above settings tell yacron2 to retry the job up to 10 times, with the delay between retries defined by an exponential backoff process: initially 1 second, doubling for every retry up to a maximum of 30 seconds. A value of -1 for maximumRetries will mean yacron2 will keep retrying forever, this is mostly useful with a schedule of "@reboot" to restart a long running process when it has failed.

If the cron job is expected to fail sometimes, you may wish to report only in the case the cron job ultimately fails after all retries and we give up on it. For that situation, you can use the onPermanentFailure option:

- name: test-01
  command: |
    echo "hello" 1>&2
    sleep 1
    exit 10
  schedule:
    minute: "*/10"
  captureStderr: true
  onFailure:
    retry:
      maximumRetries: 10
      initialDelay: 1
      maximumDelay: 30
      backoffMultiplier: 2
  onPermanentFailure:
    report:
      mail:
        from: [e-mail]
        to: [e-mail]
        smtpHost: 127.0.0.1

Concurrency

Sometimes it may happen that a cron job takes so long to execute that when the moment its next scheduled execution is reached a previous instance may still be running. How yacron2 handles this situation is controlled by the option concurrencyPolicy, which takes one of the following values:

Allow : allows concurrently running jobs (default)

Forbid : forbids concurrent runs, skipping next run if previous hasn't finished yet

Replace : cancels currently running job and replaces it with a new one

Execution timeout

If you have a cron job that may possibly hang sometimes, you can instruct yacron2 to terminate the process after N seconds if it's still running by then, via the executionTimeout option. For example, the following cron job takes 2 seconds to complete, yacron2 will terminate it after 1 second:

- name: test-03
  command: |
    echo "starting..."
    sleep 2
    echo "all done."
  schedule:
    minute: "*"
  captureStderr: true
  executionTimeout: 1  # in seconds

When terminating a job, it is always a good idea to give that job process some time to terminate properly. For example, it may have opened a file, and even if you tell it to shutdown, the process may need a few seconds to flush buffers and avoid losing data.

On the other hand, there are times when programs are buggy and simply get stuck, refusing to terminate nicely no matter what. For this reason, yacron2 always checks if a process exited some time after being asked to do so. If it hasn't, it tries to forcefully kill the process. The option killTimeout option indicates how many seconds to wait for the process to gracefully terminate before killing it more forcefully. In Unix systems, we first send a SIGTERM, but if the process doesn't exit after killTimeout seconds (30 by default) then we send SIGKILL. For example, this cron job ignores SIGTERM, and so yacron2 will send it a SIGKILL after half a second:

- name: test-03
  command: |
    trap "echo '(ignoring SIGTERM)'" TERM
    echo "starting..."
    sleep 10
    echo "all done."
  schedule:
    minute: "*"
  captureStderr: true
  executionTimeout: 1
  killTimeout: 0.5

Change to another user/group

You can request that Yacron2 change to another user and/or group for a specific cron job. The field user indicates the user (uid or userame) under which the subprocess must be executed. The field group (gid or group name) indicates the group id. If only user is given, the group defaults to the main group of that user. Example:

- name: test-03
  command: id
  schedule:
    minute: "*"
  captureStderr: true
  user: www-data

Naturally, yacron2 must be running as root in order to have permissions to change to another user.

This feature is POSIX-only (it relies on setuid/setgid). On Windows, a job with user or group set is rejected with a configuration error; see Running on Windows.

Remote web/HTTP interface

If you wish to remotely control yacron2, you can optionally enable an HTTP REST interface, with the following configuration (example):

web:
  listen:
     - http://127.0.0.1:8080
     - unix:///tmp/yacron2.sock

Enabling the web dashboard

With the web interface enabled, yacron2 also serves the web dashboard (showcased near the top of this README) at the root path (/) of any http:// listener. Open http://127.0.0.1:8080/ in the example above, and see the full dashboard tour in the wiki. It is a single self-contained page (no build step or external assets) that watches every job's status, tails its logs live, runs or cancels jobs on demand, and shows run history and a plain-English schedule preview. Logs are shown for the streams a job captures, so enable captureStdout / captureStderr on jobs whose output you want to watch here.

The run history and logs are kept in memory only. Nothing is written to disk, so the dashboard does not change yacron2's read-only-filesystem deployment story. History resets when yacron2 restarts.

If you have enabled bearer-token authentication for the web API (the web.authToken option), the dashboard page itself loads without a token, then prompts you for one and stores it only in that browser tab; every data request it makes is authenticated with that token.

To disable the dashboard and expose only the REST API, set ui: false:

web:
  listen:
     - http://127.0.0.1:8080
  ui: false

Now you have the following options to control it (using HTTPie as example):

Get the version of yacron2

$ http get http://127.0.0.1:8080/version
HTTP/1.1 200 OK
Content-Length: 22
Content-Type: text/plain; charset=utf-8
Date: Sun, 03 Nov 2019 19:48:15 GMT
Server: Python/3.7 aiohttp/3.6.2

0.10.0b3.dev7+g45bc4ce

Get the status of cron jobs

$ http get http://127.0.0.1:8080/status
HTTP/1.1 200 OK
Content-Length: 104
Content-Type: text/plain; charset=utf-8
Date: Sun, 03 Nov 2019 19:44:45 GMT
Server: Python/3.7 aiohttp/3.6.2

test-01: scheduled (in 14 seconds)
test-02: scheduled (in 74 seconds)
test-03: scheduled (in 14 seconds)

You may also get status info in json format:

$ http get http://127.0.0.1:8080/status Accept:application/json
HTTP/1.1 200 OK
Content-Length: 206
Content-Type: application/json; charset=utf-8
Date: Sun, 03 Nov 2019 19:45:53 GMT
Server: Python/3.7 aiohttp/3.6.2

[
    {
        "job": "test-01",
        "scheduled_in": 6.16588,
        "status": "scheduled"
    },
    {
        "job": "test-02",
        "scheduled_in": 6.165787,
        "status": "scheduled"
    },
    {
        "job": "test-03",
        "scheduled_in": 6.165757,
        "status": "scheduled"
    }
]

Start a job right now

Sometimes it's useful to start a cron job right now, even if it's not scheduled to run yet, for example for testing:

$ http post http://127.0.0.1:8080/jobs/test-02/start
HTTP/1.1 200 OK
Content-Length: 0
Content-Type: application/octet-stream
Date: Sun, 03 Nov 2019 19:50:20 GMT
Server: Python/3.7 aiohttp/3.6.2

Cancel a running job

POST /jobs/{name}/cancel terminates any currently-running instances of a job (the same graceful SIGTERM-then-SIGKILL sequence, honoring the job's killTimeout, that yacron2 uses elsewhere). A job cancelled this way is recorded in its history with the outcome cancelled; unlike a failure it is not reported and does not trigger retries. It returns 409 Conflict if the job is not currently running, and 404 Not Found for an unknown job.

$ http post http://127.0.0.1:8080/jobs/test-03/cancel
HTTP/1.1 200 OK

Get detailed job info (used by the dashboard)

GET /jobs returns a JSON array describing every job: its schedule and timezone, whether it is enabled/running, the time until its next scheduled run, a summary of its most recent finished run (outcome, exit code, start/finish times and duration), and a compact history of recent outcomes for the trend sparkline. This is what the web dashboard polls.

$ http get http://127.0.0.1:8080/jobs
[
    {
        "name": "test-01",
        "enabled": true,
        "schedule": "*/5 * * * *",
        "command": "echo foobar",
        "captureStdout": true,
        "captureStderr": true,
        "utc": true,
        "timezone": "UTC",
        "running": false,
        "pids": [],
        "scheduled_in": 42.1,
        "last_run": {
            "outcome": "success",
            "exit_code": 0,
            "started_at": "2026-06-21T12:00:00+00:00",
            "finished_at": "2026-06-21T12:00:01+00:00",
            "duration": 1.02,
            "fail_reason": null
        },
        "history": [
            {"outcome": "success", "duration": 0.98},
            {"outcome": "failure", "duration": 1.21},
            {"outcome": "success", "duration": 1.02}
        ]
    }
]

Get a job's run history

GET /jobs/{name}/runs returns the job's retained run history (oldest first, bounded and in memory only) together with aggregate statistics. Each run carries the same fields as last_run above; stats summarizes them. The success_rate is computed over runs that ran to completion (cancellations are excluded). Returns 404 Not Found for an unknown job.

$ http get http://127.0.0.1:8080/jobs/test-01/runs
{
    "name": "test-01",
    "runs": [
        {
            "outcome": "success",
            "exit_code": 0,
            "started_at": "2026-06-21T12:00:00+00:00",
            "finished_at": "2026-06-21T12:00:01+00:00",
            "duration": 1.02,
            "fail_reason": null
        }
    ],
    "stats": {
        "total": 1,
        "success": 1,
        "failure": 0,
        "cancelled": 0,
        "success_rate": 1.0,
        "avg_duration": 1.02,
        "min_duration": 1.02,
        "max_duration": 1.02,
        "last_duration": 1.02
    }
}

Tail a job's logs

GET /jobs/{name}/logs is a Server-Sent Events stream of a job's captured output: the most recent buffered lines first, then new lines live as a running job produces them, and finally an end event when the run finishes. Each line arrives as an event: line whose data is a JSON object {"stream": "stdout"|"stderr", "line": "..."}. Only output from the streams a job captures (captureStdout / captureStderr) is available here.

$ curl -N http://127.0.0.1:8080/jobs/test-01/logs
event: line
data: {"stream": "stdout", "line": "foobar"}

event: end
data: {}

Job-set id

The job-set id is an order-independent fingerprint of the set of jobs a yacron2 instance is running. Two instances produce the same id if and only if they hold the same set of jobs, which lets several replicas deployed from the same configuration confirm they are running the same thing, or detect that one has drifted from the others.

The id is taken over the effective (post-merge) configuration of every job, which gives it some useful properties:

• it is independent of job order, and of whether a setting was written inline on each job or hoisted into a defaults block;
• equivalent schedule spellings match: the minute:/hour: object form fingerprints the same as the equivalent five-field crontab string;
• it covers every behavior-affecting field (command, schedule, shell, the names of environment variables, capture flags, failsWhen, retry/reporting policy, timezone, enabled, and so on), so any meaningful change to a job changes the id;
• user/group are fingerprinted as configured (e.g. www-data), not as the resolved numeric uid/gid, which can differ host to host;
• secret/value material is never embedded: inline reporting secrets (Sentry DSN, mail password) are redacted, and only the names of environment variables are hashed, not their values (env commonly holds secrets, and a per-host value, e.g. from env_file, would otherwise make identical configs differ across hosts). The id is safe to log and serve, and rotating a secret or changing an env value does not change it.

Because it reflects effective config, it also reflects platform-dependent defaults (the default shell is /bin/sh on POSIX, cmd.exe on Windows), so compare instances running on the same platform, which replicas are. The scheme is versioned with a v1: prefix; ids are only comparable within a scheme version.

It is available three ways:

• CLI: print it and exit (handy in scripts / health checks):

  $ yacron2 -c /etc/yacron2.d --job-set-id
  v1:b834d7565aee0da50cd017f666651a5ba3b2e6b161daf0cb6e430f23f51ce90b
  

• HTTP: GET /job-set-id on the web interface (also application/json), and shown in the dashboard header:

  $ http get http://127.0.0.1:8080/job-set-id
  v1:b834d7565aee0da50cd017f666651a5ba3b2e6b161daf0cb6e430f23f51ce90b
  
  $ http get http://127.0.0.1:8080/job-set-id Accept:application/json
  {"job_set_id": "v1:b834d7…51ce90b", "jobs": 3}
  

• Logs: it is logged once at startup, and again whenever a config reload changes it.

Clustering and leader election

By default yacron2 runs as a single instance and every replica runs every job. An optional cluster section lets several replicas coordinate: each node serves a small GET /peer endpoint over mutual TLS and periodically polls its configured peers, comparing job-set ids so they can confirm they are running the same set of jobs (cluster peer attestation). Turning on electLeader promotes that same attestation into a quorum-gated leader election, so you can run more than one replica from one config without double-running scheduled jobs:

cluster:
  listen: "0.0.0.0:8443"          # the mTLS listener for this node
  tls:
    ca:   /etc/yacron2/cluster-ca.pem   # trust anchor for peer certificates
    cert: /etc/yacron2/this-node.pem    # this node's certificate
    key:  /etc/yacron2/this-node.key
  peers:
    - host: yacron-b.internal:8443
    - host: yacron-c.internal:8443
  nodeName: yacron-a              # optional; defaults to the system hostname
  interval: 30                    # optional; seconds per round (default 30)
  connectTimeout: 10              # optional; per-peer connect timeout (default 10)
  driftAfter: 3                   # optional; rounds before "drifted" (default 3)
  electLeader: true               # observe-only if false (the default)

Each node independently elects, as leader, the lowest nodeName among the members it currently sees agreeing on the job-set id, but only if that set is a quorum (a strict majority) of the cluster, so under a clean partition at most one side leads. This is best-effort (the default gossip backend keeps no shared state); for a fenced, exactly-once guarantee set cluster.backend: kubernetes or cluster.backend: etcd to elect through a coordination.k8s.io/v1 Lease or a lease-bound etcd key instead.

Each job can override the cluster-wide default with a per-job clusterPolicy, picking its own point on the liveness-vs-duplication trade-off:

clusterPolicy	healthy (quorate)	partitioned / sub-quorum	use for
Leader (default)	leader runs once	nobody runs (skips)	non-idempotent jobs where a duplicate is harmful and an occasional skip is OK (billing, outbound email)
PreferLeader	lowest node runs once	each side's lowest node runs (may double-run)	important and idempotent jobs that should never skip
EveryNode	every node runs	every reachable node runs	genuinely per-node work (local log rotation), or fully idempotent jobs

The current view (members, elected leader, quorum, and any conflicts) is available at GET /cluster and shown as a panel in the dashboard. This is a teaser: the full trust model, per-peer status table, quorum math, sizing guidance, distribution: spread load-balancing, and the fenced lease backends are all covered in depth in the Clustering and Leader Election guide in the wiki. To watch it live, see Try it below.

Includes

You may have a use case where it's convenient to have multiple config files, and choose at runtime which one to use. In that case, it might be useful if you can put common definitions (such as defaults for reporting, shell, etc.) in a separate file, that is included by the other files.

To support this use case, it is possible to ask one config file to include another one, via the include directive. It takes a list of file names: those files will be parsed as configuration and merged in with this file.

Example, your main config file could be:

include:
  - _inc.yaml

jobs:

  - name: my job
    ...

And your included _inc.yaml file could contain some useful defaults:

defaults:
  shell: /bin/bash
  onPermanentFailure:
    report:
      sentry:
        ...

Custom logging

It's possible to provide a custom logging configuration, via the logging configuration section. For example, the following configuration displays log lines with an embedded timestamp for each message.

logging:
  # In the format of:
  # https://docs.python.org/3/library/logging.config.html#dictionary-schema-details
  version: 1
  disable_existing_loggers: false
  formatters:
    simple:
      format: '%(asctime)s [%(processName)s/%(threadName)s] %(levelname)s (%(name)s): %(message)s'
      datefmt: '%Y-%m-%d %H:%M:%S'
  handlers:
    console:
      class: logging.StreamHandler
      level: DEBUG
      formatter: simple
      stream: ext://sys.stdout
  root:
    level: INFO
    handlers:
      - console

Obscure configuration options

enabled: true|false (default true)

It is possible to disable a specific cron job by adding a enabled: false option. Jobs with enabled: false will simply be skipped, as if they aren't there, apart from validating the configuration.

jobs:
  - name: test-01
    enabled: false  # this cron job will not run until you change this to `true`
    command: echo "foobar"
    shell: /bin/bash
    schedule: "* * * * *"

Contributing

Development setup, the test/lint/type-check workflow, and the automated release process (including the commit-message marker that triggers a PyPI release) are documented in CONTRIBUTING.md.