zrepl/docs/content/configuration/jobs.md

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title = "Job Types"
weight = 10
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A *job* is the unit of activity tracked by the zrepl daemon and configured in the [configuration file]({{< relref "install/_index.md#configuration-files" >}}).

Every job has a unique `name`, a `type` and type-dependent fields which are documented on this page.

Check out the [tutorial]({{< relref "tutorial/_index.md" >}}) and {{< sampleconflink >}} for examples on how job types are actually used.

## Job Types

### Source

|Parameter|Default|Description / Example|
|-----|-------|-------|
|`type`||`source`|
|`name`||unique name of the job|
|`serve`||{{< zrepl-transport "serve transport" >}} specification|
|`datasets`||{{< zrepl-filter >}} for datasets to expose to client|
|`snapshot_prefix`||prefix for ZFS snapshots taken by this job|
|`interval`||snapshotting interval|
|`prune`||{{< zrepl-prune >}} policy for datasets in `datasets` with prefix `snapshot_prefix`|

* Snapshotting Task (every `interval`, {{% zrepl-job-patient %}})
    1. A snapshot of filesystems matched by `datasets` is taken every `interval` with prefix `snapshot_prefix`.
    1. The `prune` policy is triggered on datasets matched by `datasets` with snapshots matched by `snapshot_prefix`.
* Serve Task
    * Wait for connections from pull job using `serve`

A source job is the counterpart to a [pull job]({{< relref "#pull" >}}).

Example: {{< sampleconflink "pullbackup/productionhost.yml" >}}

### Pull

|Parameter|Default|Description / Example|
|-----|-------|-------|
|`type`||`pull`|
|`name`||unique name of the job|
|`connect`||{{< zrepl-transport "connect transport" >}} specification|
|`interval`||Interval between pull attempts|
|`mapping`||{{< zrepl-mapping >}} for remote to local filesystems|
|`initial_repl_policy`|`most_recent`|initial replication policy|
|`snapshot_prefix`||prefix filter used for replication & pruning|
|`prune`||{{< zrepl-prune >}} policy for local filesystems reachable by `mapping`|

* Main Task (every `interval`, {{% zrepl-job-patient %}})
    1. A connection to the remote source job is established using the strategy in `connect`
    1. `mapping` maps filesystems presented by the remote side to local *target filesystems*
    1. Those remote filesystems with a local *target filesystem* are replicated:
        1. Only snapshots with prefix `snapshot_prefix` are replicated.
        1. If possible, incremental replication takes place.
        1. If the local target filesystem does not exist, `initial_repl_policy` is used.
        1. On conflicts, an error is logged but replication of other filesystems with mapping continues.
    1. The `prune` policy is triggered for all *target filesystems*


A pull job is the counterpart to a [source job]({{< relref "#source" >}}).

Example: {{< sampleconflink "pullbackup/backuphost.yml" >}}

### Local

|Parameter|Default|Description / Example|
|-----|-------|-------|
|`type`||`local`|
|`name`||unique name of the job|
|`mapping`||{{<zrepl-mapping>}} from source to target filesystem (both local)|
|`snapshot_prefix`||prefix for ZFS snapshots taken by this job|
|`interval`|snapshotting & replication interval|
|`initial_repl_policy`|`most_recent`|initial replication policy|
|`prune_lhs`||pruning policy on left-hand-side (source)|
|`prune_rhs`||pruning policy on right-hand-side (target)|

* Main Task (every `interval`, {{% zrepl-job-patient %}})
    1. Evaluate `mapping` for local filesystems, those with a *target filesystem* are called *mapped filesystems*.
    1. Snapshot *mapped filesystems* with `snapshot_prefix`.
    1. Replicate *mapped filesystems* to their respective *target filesystems*:
        1. Only snapshots with prefix `snapshot_prefix` are replicated.
        1. If possible, incremental replication takes place.
        1. If the *target filesystem* does not exist, `initial_repl_policy` is used.
        1. On conflicts, an error is logged but replication of other *mapped filesystems* continues.
    1. The `prune_lhs` policy is triggered for all *mapped filesystems*
    1. The `prune_rhs` policy is triggered for all *target filesystems*

A local job is combination of source & pull job executed on the same machine.

Example: {{< sampleconflink "localbackup/host1.yml" >}}

## Glossary

#### Task

A job consists of one or more tasks and a task consists of one or more steps.
Some tasks may be periodic while others wait for an event to occur.

#### patient

it is supposed to execute some task every `interval`.
We call the start of the task an *invocation*.

* If the task completes in less than `interval`, the task is restarted at `last_invocation + interval`.
* Otherwise, a patient job
    * logs a warning as soon as a task exceeds its configured `interval`
    * waits for the last invocation to finish
    * logs a warning with the effective task duration
    * immediately starts a new invocation of the task