Repository Management

Repositories are the containers for the components provided to your users as explained in more detail in Repository Manager Concepts. Creating and managing repositories is an essential part of your Nexus Repository configuration, since it allows you to expose more components to your users. It supports proxy repositories, hosted repositories and repository groups in a number of different repository formats.

To manage repositories select the Repositories item in the Repository sub menu of the Administration menu.

The binary parts of a repository are stored in blob stores, which can be configured by selecting Blob Stores from the Repository sub menu of the Administration menu.

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Repository Types

Proxy Repository

A repository with the type proxy, also known as a proxy repository, is a repository that is linked to a remote repository. Any request for a component is verified against the local content of the proxy repository. If no local component is found, the request is forwarded to the remote repository. The component is then retrieved and stored locally in the repository manager, which acts as a cache. Subsequent requests for the same component are then fulfilled from the local storage, therefore eliminating the network bandwidth and time overhead of retrieving the component from the remote repository again.

By default, the repository manager ships with the following configured proxy repositories:

maven-central

This proxy repository accesses the Central Repository, formerly known as Maven Central. It is the default component repository built into Apache Maven and is well-supported by other build tools like Gradle, SBT or Ant/Ivy.

nuget.org-proxy

This proxy repository accesses the NuGet Gallery. It is the default component repository used by the nuget package management tool used for .Net development.

Hosted Repository

A repository with the type hosted, also known as a hosted repository, is a repository that stores components in the repository manager as the authoritative location for these components.

By default, the repository manager ships with the following configured hosted repositories:

maven-releases

This hosted repository uses the maven2 repository format with a release version policy. It is intended to be the repository where your organization publishes internal releases. You can also use this repository for third-party components that are not available in external repositories and can therefore not be retrieved via a configured proxy repository. Examples of these components could be commercial, proprietary libraries such as an Oracle JDBC driver that may be referenced by your organization.

maven-snapshots

This hosted repository uses the maven2 repository format with a snapshot version policy. It is intended to be the repository where your organization publishes internal development versions, also known as snapshots.

nuget-hosted

This hosted repository is where your organization can publish internal releases in repository using the nuget repository format. You can also use this repository for third-party components that are not available in external repositories, that could potentially be proxied to gain access to the components.

Repository Group

A repository with the type group, also known as repository group, represents a powerful feature of Nexus Repository Manager. They allow you to combine multiple repositories and other repository groups in a single repository. This in turn means that your users can rely on a single URL for their configuration needs, while the administrators can add more repositories and therefore components to the repository group.

When a user is given a privilege to a group repository, then that user will also have that privilege to all transitive members of that group repository only when their request is directed to the group repository. Direct requests to indvidual member repositories will only work if the user is given explicit permission to the individual repository.

The repository manager ships with the following groups:

maven-public

The maven-public group is a repository group of maven2 formatted repositories and combines the important external proxy repository for the Central Repository with the hosted repositories maven-releases and maven-snapshots. This allows you to expose the components of the Central Repository as well as your internal components in one single, simple-to-use repository and therefore URL.

nuget-group

This group combines the nuget formatted repositories nuget-hosted and nuget.org-proxy into a single repository for your .Net development with NuGet.

Managing Repositories and Repository Groups

The administration user interface for repositories and repository groups is available via the Repositories item in the Repository sub menu of the Administration menu. It allows you to create and configure repositories as well as delete them and perform various maintenance operations. To access this section, the user must have the nx-all or nx-repository-admin privileges. The initial view displayed in Figure: “List of Repositories” features a list of all configured repositories and repository groups.

Figure: List of Repositories

The list of repositories displays some information for each repository in the following columns:

  • Name - the unique name of the repository or repository group
  • Type - the type of the repository with values of proxy or hosted for repositories or group for a repository group
  • Format - the repository format used for the storage in the repository with values such as maven2nuget or others
  • Status - the status of the repository as well as further information about the status:
    • Online - Uninitialised means that the proxy repository is newly created and not yet initialised; this status will change to Online - Ready to Connect when initialisation is complete
    • Online - Ready to Connect means the proxy repository is ready to connect to remote, but no request has been made to that proxy yet
    • Online - Remote Available means requests have already been made to that proxy repository, and connecting to remote was successful
    • Online - Remote Manually Blocked means that the Auto blocking enabled checkbox in this proxy repository's settings is checked
    • Online - Remote Auto Blocked and Unavailable indicates that a remote repository is unreachable/unresponsive and the Auto blocking enabled checkbox in the proxy repository's settings is checked
    • Online - Remote Unavailable indicates that a remote repository is unreachable/unresponsive and the Auto blocking enabled checkbox in the proxy repository's settings is not checked
    • Offline - Repository Offline means that the Online checkbox in a repository's settings is not checked
    • Offline indicates that the Online checkbox in a group/hosted repository's settings is not checked
  • URL - the copy button prompts a dialog containing a direct URL path exposing the repository
  • Health Check - displays the repository health statistics from a previously run Repository Health Check or a button to start the analysis

The Create repository button above the repository list triggers a dialog to select the Recipe for the new repository. The recipe combines the format and the type of repository into a single selection. Depending on your repository manager version and installed plugins, the list of available choices differs.

For example to create another release repository in maven2 format, you would click on the row with the recipe maven2 (hosted) in the dialog. If you wanted to proxy a maven2 repository, choose maven 2 (proxy). On the other hand if you want to proxy a NuGet repository, choose nuget (proxy). With maven2 (group) you can create a repository group for maven2 repositories.

After this selection, you are presented with the configuration view, that allows you to fill in the required parameters and some further configuration. The exact details on the view depend on the selected repository provider and are identical to the administration for updating the configuration of a repository documented in the following sections.

Once you have created a repository or repository group, it is available in the list for further configuration and management. Clicking on a specific row allows you to navigate to this repository specific administration section. An example for the maven-central repository is partially displayed in Figure: “Partial Repository Configuration for a Proxy Repository”.

Figure: Partial Repository Configuration for a Proxy Repository

The repository administration feature view has buttons to perform various actions on a repository. The buttons displayed depend on the repository format and type. The following buttons can be found:

Delete repository

The Delete repository button allows you to delete the repository and all related configuration and components, after confirming the operation in a dialog.

Invalidate cache

The Invalidate cache button invalidates the caches for this repository. The exact behavior depends on the repository type:

  • Proxy repositories

Invalidating the cache on a proxy repository clears the proxy cache such that any items cached as available will be checked again for any changes the next time they are requested. This also clears the negative cache for the proxy repository such that any items that were not found within the defined cache period will be checked again the next time they are requested.

  • Repository groups

Invalidating the cache of a repository group, clears the group cache such that any items fetched and held in the group cache, such as Maven metadata, will be cleared. This action also invalidates the caches of any proxy and group repositories that are members of this group.

Rebuild Index

The Rebuild Index button allows you to drop and recreate the search index for the proxy repository, synchronizing the contents with search index. This button is only available for proxy repositories.

The following properties can be viewed for all repositories and can not be edited after the initial creation of the repository:

Name

The Name is the identifier that will be used in the URL for access to the repository. For example, the proxy repository for the Central Repository has a name of maven-central. The Name must be unique in a given repository manager installation and is required.

Format

Format defines in what format the repository manager exposes the repository to external tools. Supported formats depend on the edition of the repository manager and the installed plugins. Examples are maven2nugetrawdockernpm.

Type

The type of repository - proxy, hosted, or group.

URL

It shows the user facing URL this means that Maven and other tools can access the repository directly at e.g., http://localhost:8081/repository/maven-central.

Online

The checkbox allows you set whether this repository is available to client side tools or not.

Beyond the generic fields used for any repository, a number of different fields are used and vary depending on the repository format and type. They are grouped under a number of specific headers that include configuration for the related aspects detailed below.

Storage

Every repository needs to have a blob store configured to determine where components are stored. The drop-down allows you to select from all the configured blob stores. Documentation about creating blob stores can be found in the Storage Guide.

The Strict Content Type Validation allows you to activate a validation that checks the MIME type of all files published into a repository to conform to the allowed types for the specific repository format.

Cleanup Policies

This section, shown in Figure: Cleanup Policies subsection, provides a list of cleanup policies that can be used against hosted and proxy repositories. When the Admin - Cleanup repositories using their associated policies task is executed it pares the contents of that repository against all Applied policies by deleting contents that match any of them. Ultimately, this is a way of controlling your disk space and making sure unused items are removed from Nexus Repository. The use of this area is optional and by default the Applied section is empty.

The lists will only include cleanup policies you have created for the respective format. See here for more about creating and maintaining cleanup policies.


Figure: Cleanup Policies subsection

Groups do not use cleanup policies themselves, they simply contain the components from their children.

It is important to note that any component affected by ANY policy in the Applied section will be deleted. So if you have a policy that deletes only X and a policy that deletes only Y, both X and Y will be removed when the task executes if both policies are Applied.

Hosted

A hosted repository includes configuration of a Deployment policy in the Hosted configuration section. Its setting controls how a hosted repository allows or disallows component deployment.

If the policy is set to Read-only, no deployment is allowed.

If this policy is set to Disable redeploy, a client can only deploy a particular component once and any attempt to deploy a component again will result in an error. The disabled redeploy is the default value, since most client tools assume components to be immutable and will not check a repository for changed components that have already been retrieved and cached locally.

If the policy is set to Allow redeploy, clients can deploy components to this repository and overwrite the same component in subsequent deployments.

If you are using replication, this policy is automatically set to Deploy by Replication Only. This will block all deployment to the hosted repository except by the internal replication mechanism. You should not manually set this policy to Deploy by Replication Only. If you disable replication, Nexus Repository automatically restores your previous deployment policy.

Proxy

The configuration for proxy repositories in the Proxy section also contains the following parameters:

Remote Storage

A proxy repository on the other hand requires the configuration of the Remote Storage. It needs to be configured with the URL of the remote repository, that should to be proxied. When selecting the URL to proxy it is beneficial to avoid proxying remote repository groups. Proxying repository groups prevents some performance optimization in terms of accessing and retrieving the content of the remote repository. If you require components from the group that are found in different hosted repositories on the remote repository server it is better to create multiple proxy repositories that proxy the different hosted repositories from the remote server on your repository manager instead of simply proxying the group.

Use the Nexus truststore

This checkbox allows you to elect for the repository manager to manage the SSL certificate of the remote repository. It is only displayed - if the remote storage uses a HTTPS URL. The View certificate button triggers the display of the SSL certificate details in a dialog. The dialog allows you to add or remove the certificate from the certificate truststore maintained by the repository manager. Further details are documented in Outbound SSL - Trusting SSL Certificates of Remote Repositories.

Blocked

Setting a repository to blocked causes the repository manager to no longer send outbound requests to the remote repository.

Auto blocking enabled

If Auto blocking enabled is set to true, the repository manager automatically blocks a proxy repository if the remote repository becomes unavailable. While a proxy repository is blocked, components will still be served to clients from a local cache, but the repository manager will not attempt to locate a component in a remote repository. The repository manager periodically retests the remote repository and unblocks it once it becomes available.

Maximum component age

When the proxy receives a request for a component, it does not request a new version from the remote repository until the existing component is older than Maximum component age.

Maximum metadata age

The repository manager retrieves metadata from the remote repository. It will only retrieve updates to metadata after the Maximum metadata age has been exceeded. If the metadata is component metadata, it uses the longer of this value and Maximum component age before rechecking.

Negative Cache

Not found cache enabled/Not found cache TTL

If the repository manager fails to locate a component, it will cache this result for a given number of minutes. In other words, if the repository manager can’t find a component in a remote repository, it will not perform repeated attempts to resolve this component until the Not found cache TTL time has been exceeded. The default for this setting is 1440 minutes (or 24 hours) and this cache is enabled by default.

HTTP

The HTTP configuration section allows you to configure the necessary details to access the remote repository, even if you have to provide authentication details in order to access it successfully or if you have to connect to it via a proxy server.

This configuration is only necessary, if it is specific to this repository. Global HTTP proxy and authentication is documented in HTTP and HTTPS Request and Proxy Settings.

Authentication

This section allows you to select Username or Windows NTLM as Authentication type. Subsequently you can provide the required Username and Password for plain authentication or UsernamePasswordWindows NTLM hostname and Windows NTLM domain for Windows NTLM-based authentication.

HTTP request settings

In the HTTP request settings you can change properties of the HTTP requests to the remote repository. The values you can apply to this section are as follows:

    • User-agent customization - Enter the string to be appended to user-agent HTTP headers.
    • Connection retries - Enter the total number of connection attempts after an initial timeout.
    • Connection timeout - Set the timeout interval for requests, in seconds.
    • Enable circular redirects - Allow proxy repositories to follow redirects indicated by the remote server even if they point to an already processed URL.
    • Enable cookies - Authorize HTTP cookies sent by the remote server, for future requests.

https://maven.oracle.com is a server that requires both Enable circular redirects and Enable cookies. This is because, when requesting data you are redirected to a queue of different URLs, most of which are involved with authentication.

By enabling these options, you allow the repository manager to maintain the authentication state in a cookie that would be sent with each request, eliminating the need for the authentication-related redirects and avoiding timeouts.

Changes made to HTTP request settings are applied to all HTTP requests made from the repository manager to the remote repository being proxied. Enabling these settings will override any general settings defined in HTTP and HTTPS Request and Proxy Settings. 

Some repository formats include configuration options, such as these formats:

Repository Groups

The creation and configuration for a repository group differs a little from pure repositories. It allows you to manage the member repositories of a repository group. An example for a repository group using the maven2 format is visible in Figure: “Repository Group Configuration”. In this figure you can see the contents of the maven-public group that is pre-configured in Nexus Repository.

Figure: Repository Group Configuration

The Format and Type are determined by the selection of the provider in the creation dialog e.g., maven2 (group) for the maven-public as a maven2 format repository group.

The Name is set during the creation and is fixed once the repository group is created.

The Online checkbox allows you set whether this repository group is available to client side tools or not.

The Member repositories selector allows you to add repositories to the repository group as well as remove them. The Members column includes all the repositories that constitute the group. The Available column includes all the repositories and repository groups that can potentially be added to the group.

Note that the order of the repositories listed in the Member section is important. When the repository manager searches for a component in a repository group, it will return the first match. To reorder a repository in this list, click and the drag the repositories and groups in the Members list or use the arrow buttons between the Available and Members list. These arrows can be used to add and remove repositories as well.

The order of repositories or other groups in a group can be used to influence the effective metadata that will be retrieved from a repository group. It is recommended practice to place hosted repositories higher in the list than proxy repositories. For proxy repositories, the repository manager may need to check the remote repository which will incur more overhead than a hosted repository lookup.

It is also recommended to place repositories with a higher probability of matching the majority of components higher in this list. If most of your components are going to be retrieved from the Central Repository, putting maven-central higher in this list than a smaller, more focused repository is going to be better for performance, as the repository manager is not going to interrogate the smaller remote repository for as many missing components. These best practices are implemented in the default configuration.

Blob Stores

A blob store is the internal storage mechanism for the binary parts of components and their assets. They can be local file system or cloud-based using Amazon S3 (Pro and OSS) or Microsoft Azure (Pro only). Each blob store can be used by one or multiple repositories and repository groups. You can learn more about blob stores and how to configure them as well as planning your storage strategy in the Storage Guide.