Minimal API¶

The minimal job API offers another way of defining a cron job. It favors simplicity over feature richness. A job can be defined as such:

builder.Services.AddNCronJob(() => { }, "0 * * * *");

This call will register all the necessary services and the job in question. The method can be called multiple times to register multiple jobs:

builder.Services.AddNCronJob(() => { }, "0 * * * *");
builder.Services.AddNCronJob(() => { }, "1 * * * *");

The minimal job API does support resolving services from the DI container. The following example demonstrates how to resolve a logger and a TimeProvider:

builder.Services.AddNCronJob((ILogger<Program> logger, TimeProvider timeProvider) =>
{
    logger.LogInformation("Hello World - The current date and time is {Time}", timeProvider.GetLocalNow());
}, "*/5 * * * * *");

Also the JobExecutionContext and CancellationToken can be resolved from the DI container:

builder.Services.AddNCronJob((IJobExecutionContext context, CancellationToken token) =>
{

}, "*/5 * * * * *");

The token can be used to get notified when the job should be cancelled (for example if the whole application gets shut down).

Of course functions can be asynchrnous in nature as well:

builder.Services.AddNCronJob(async (HttpClient httpClient) =>
{
    using var response = await httpClient.GetAsync("https://github.com/NCronJob-Dev/NCronJob");
    var content = await response.Content.ReadAsStringAsync();
}, "*/5 * * * * *");

There are certain restrictions that can’t be enforced at compile time (due to a missing interface) which will lead to a runtime exception:

• The job has to return void or Task, otherwise an InvalidOperationException will be thrown.

Retry-Support¶

The minimal job API does support the Retry model as well. The minimal job API leverages the fact that lambdas also can have attributes:

builder.Services.AddNCronJob([RetryPolicy(retryCount: 3)] () => { }, "0 * * * *");

To know in which attempt the job currently is, the JobExecutionContext can be used:

builder.Services.AddNCronJob([RetryPolicy(retryCount: 3)] (IJobExecutionContext context) => 
{
    if(context.Attempts == 1)
    {
        // First attempt
    }
}, "0 * * * *");

Time Zone¶

The time zone can be controlled as well and defaults to UTC if not specified:

builder.Services.AddNCronJob(() => { }, "0 * * * *", TimeZoneInfo.Local);

Concurrency-Support¶

In the same way, the concurrency level can be controlled (see Concurrency):

builder.Services.AddNCronJob([SupportsConcurrency(2)] () => { }, "0 * * * *");

Now, the job can only be executed by two instances at the same time.

Restrictions¶

The minimal API has some restrictions over the “full approach”:

• Some errors can only be detected at runtime (for example if the job does not return void or Task).

Minimal API for instant Jobs¶

The minimal API also supports instant jobs, for this check out the Instant Jobs documentation.

Minimal API for dependent jobs¶

The minimal API also supports dependent jobs, for this check out the Dependent Jobs documentation.