Introduction to Tapis Apps
A Tapis application represents a piece of software that can be executed on one or more Tapis systems producing useful results. Each application is versioned and is owned by a specific user who has special privileges for the application. Once an application is defined, users can execute it on a specific system using the Jobs service. A Tapis job represents a single execution of an app. We’ll discuss jobs next, but for now, an application definition includes information which allows the Jobs service to:
- Stage input prior to launching the application
- Launch the application
- Monitor the application during execution
- Archive output after application execution
Versioning
Applications are expected to evolve over time. An initial version will be created and may enjoy widespread use. When the application must be modified it is important to allow for previous versions of the application to be used while new versions are created and tested.
The versioning scheme is at the discretion of the application author. It is recommended that a two or three level form of semantic versioning be used. The fully qualified application reference within a tenant is constructed by appending a hyphen to the name followed by the version string. For example, the first two versions of an application might be myapp-0.0.1 and myapp-0.0.2. If a version is not specified when retrieving an application then by default the most recently created version of the application will be returned.
Model
An application contains some information that is independent of the version and some information that varies by version. At a high level an application represents the following information:
Non-Versioned Attributes
- id - A short descriptive name for the application that is unique within the tenant.
- owner - A specific user set at application creation. Default is
${apiUserId}, the user making the request to create the application.
Versioned Attributes
- version - Applications are expected to evolve over time.
Id+versionmust be unique within a tenant. - description - An optional more verbose description for the application.
- runtime - Runtime to be used when executing the application. DOCKER, SINGULARITY. Default is DOCKER.
- containerImage - Reference to be used when running the container image.
- maxJobs - Maximum total number of jobs that can be queued or running for this application on a given execution
system at a given time. Note that the execution system may also limit the number of jobs on the system which may further restrict the total number of jobs. Set to -1 for unlimited. Default is unlimited. - maxJobsPerUser - Maximum total number of jobs associated with a specific job owner that can be queued or running for this application on a given execution system at a given time. Note that the execution system may also limit the number of jobs on the system which may further restrict the total number of jobs. Set to -1 for unlimited. Default is unlimited.
- strictFileInputs - Flag indicating if a job request is allowed to have unnamed file inputs. If set to true then a job request may only use the named file inputs defined in the application. See attribute fileInputs in the JobAttributes table. Default is false.
- Job related attributes - Various attributes related to job execution such as execSystemId, execSystemExecDir, execSystemInputDir, execSystemLogicalQueue archiveSystemId, fileInputs, etc. Many of these are optional.
Next Steps
Next we’ll actually look at what is involved with registering a specific application.
Next-> Creating and Registering a Classifier App
Additional Resources
For more information about applications and the Applications service please see Tapis Applications Service documentation.