Configuring with Git

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Overview

Git is a distributed version control system (DVCS). It encourages parallel development through simplified branching and merging, optimizes performance by conducting many operations on the local copy of the repository, and uses SHA-1 hashes for checksums to assure integrity and guard against corruption of repository data. For more information about Git, see the documentation.

Spring Cloud Config provides a Git backend so that the Spring Cloud Config Server can serve configuration stored in Git. The Spring Cloud Services Config Server supports this backend and can serve configuration stored in Git to client apps when given the URL to a Git repository (for example, the URL of a repository hosted on GitHub or Bitbucket). For more information about Spring Cloud Config’s Git backend, see the documentation.

See below for information about configuring a Config Server service instance to use Git for configuration sources.

General Configuration

Parameters used to configure configuration sources are part of a JSON object called git, as in {"git": { "uri": "https://example.com/config" } }. General parameters used to configure the Config Server’s default configuration source are listed below.

Parameter Function
uri The URI (http://, https://, or ssh://) of a Git repository. Required
label The default “label” used if a request is received without a label. Default value: master
searchPaths A pattern used to search for configuration-containing subdirectories in the repository
username The username used to access the repository (if protected by HTTP Basic authentication)
password The password used to access the repository (if protected by HTTP Basic authentication)
refreshRate Interval, in seconds, between refreshes of the Config Server’s repository clone when a client requests configuration
periodic Added in Spring Cloud Services 3.1.2. Whether the Config Server should periodically update its mirror of the Git repository with any changes from the external repository. If set to true, the Config Server will update the mirror every 5 minutes. Valid values: true, false
skipSslValidation For a https:// URI, whether to skip validation of the SSL certificate on the repository’s server. Valid values: true, false
cloneOnStart Whether the Config Server should clone the default repository when it starts up (by default, the Config Server will only clone the repository when configuration is first requested from the repository). Valid values: true, false
update-git-repos Used only with cf update-service; causes the mirror service to update a Config Server’s Git repository mirrors. Valid values: true

You can set label to a branch name, a tag name, or a specific Git commit hash. To set label to point to the develop branch of a repository, you might configure settings as in the following:

cf create-service p.config-server standard config-server -c '{"git": { "uri": "https://github.com/myorg/config-repo", "label": "develop" } }'

To set label to point to the v1.1 tag in a repository, you might configure settings as shown in the following command:

cf create-service p.config-server standard config-server -c '{"git": { "uri": "https://github.com/myorg/config-repo", "label": "v1.1" } }'

Within a client app, you can override the Config Server’s label setting by setting the spring.cloud.config.label property (for example, in bootstrap.yml).

spring:
  cloud:
    config:
      label: v1.2

To refresh a Config Server’s Git repository mirrors and retrieve new configuration property values, run the cf update-service command, passing the update-git-repos flag with value true:

cf update-service my-config-server -c '{"update-git-repos": true }'

Encryption and Encrypted Values

Note: This feature was added in Spring Cloud Services for VMware Tanzu v3.1.6.

The Config Server can serve encrypted property values from a configuration file. If the Config Server is configured with a symmetric or asymmetric encryption key and the encrypted values are prefixed with the string {cipher}, the Config Server will decrypt the values before serving them to client apps.

The parameters used to configure decryption for a Config Server are listed below.

Parameter Function
encrypt.key The key to use for decryption.

To configure a Config Server service instance that can decrypt property values, use the following command:

cf create-service p-config-server standard config-server -c '{"git": {"uri": "https://github.com/spring-cloud-services-samples/cook-config.git" }, "encrypt": { "key": "KEY" }}'

If you wish to use public-key (or asymmetric) encryption, you may configure the Config Server to use a PEM-encoded keypair. You might generate such a keypair using, for example, OpenSSL on the command line:

$ openssl genpkey -algorithm RSA -outform PEM -pkeyopt rsa_keygen_bits:2048 > server.key
# Translate PEM encoded private key to a RSA private key and escape newlines
$ openssl rsa -in server.key | awk '{printf "%s\\n", $0}' > server_rsa.key

Important: The key must be correctly formatted in order to be usable by the Config Server. Either use the above commands or ensure that you otherwise create a similar PEM-encoded keypair. The beginning of the key should include BEGIN RSA PRIVATE KEY.

To configure a Config Server service instance that can decrypt property values using an assymetric keypair, use the following JSON object, where the value of key is the content of the server_rsa.key file:

'{"git": {"uri": "https://github.com/spring-cloud-services-samples/cook-config.git" }, "encrypt": { "key": "-----BEGIN RSA PRIVATE KEY-----\nMIIE......\n-----END RSA PRIVATE KEY-----" }}'

The encryption key is masked in the Config Server dashboard.

SSH Repository Access

You can configure a Config Server configuration source so that the Config Server accesses it using the Secure Shell (SSH) protocol. To do so, you must specify a URI using the ssh:// URI scheme or the Secure Copy Protocol (SCP) style URI format, and you must supply a private key. You may also supply a host key with which the server will be identified. If you do not provide a host key, the Config Server will not verify the host key of the configuration source’s server.

A SSH URI must include a username, host, and repository path. This might be specified as shown in the following command:

cf create-service p.config-server standard config-server -c '{"git": { "uri": "ssh://git@github.com/spring-cloud-services-samples/cook.git"} }'

An equivalent SCP-style URI might be specified as shown in the following command:

cf create-service p.config-server standard config-server -c '{"git": { "uri": "git@github.com:spring-cloud-services-samples/cook-config.git"} }'

The parameters used to configure SSH for a Config Server configuration source’s URI are listed below.

Parameter Function
hostKey The host key of the Git server. If you have connected to the server via git on the command line, this is in your .ssh/known_hosts. Do not include the algorithm prefix; this is specified in hostKeyAlgorithm. (Optional.)
hostKeyAlgorithm The algorithm of hostKey: one of “ssh-dss”, “ssh-rsa”, “ecdsa-sha2-nistp256”, “ecdsa-sha2-nistp384”, and “ecdsa-sha2-nistp521”. (Required if supplying hostKey.)
privateKey The private key that identifies the Git user, with all newline characters replaced by \n. Passphrase-encrypted private keys are not supported.
strictHostKeyChecking Whether the Config Server should fail to start if it encounters an error when using the provided hostKey. (Optional.) Valid values are true and false. Default is true.

To configure a Config Server service instance that uses SSH to access a configuration source, allowing for host key verification, use the following command:

cf create-service p.config-server standard config-server -c '{"git": { "uri": "ssh://git@github.com/spring-cloud-services-samples/cook.git", "hostKey": "EXAMPLEcccc1yc2EAAAABIwAAAQEAq2A7hRGmdnm9tUDbO9IDSwBK6TbQa+...", "hostKeyAlgorithm": "ssh-rsa", "privateKey": "-----BEGIN EXAMPLE RSA PRIVATE KEY-----\nMIIJKQIB..."} }'

To configure a Config Server service instance that uses SSH to access a configuration source, without host key verification, use the following command:

cf create-service p.config-server standard config-server -c '{"git": { "uri": "ssh://git@github.com/spring-cloud-services-samples/cook.git", "privateKey": "-----BEGIN EXAMPLE RSA PRIVATE KEY-----\nMIIJKQIB..."} }'

HTTP(S) Proxy Repository Access

You can configure a Config Server service instance to access configuration sources using an HTTP or HTTPS proxy. To do so, you must provide proxy settings in either of the git.proxy.http or git.proxy.https JSON objects. You can set the proxy host and port, the proxy username and password (if applicable), and a list of hosts which the Config Server should access outside of the proxy.

Note: If you are using a composite backend with multiple Git repositories that are accessed using the same proxy, you must provide the proxy’s settings for each git object.

Settings for an HTTP proxy are set in the git.proxy.http object. These might be set as shown in the following command:

cf create-service p.config-server standard config-server -c '{"git": { "proxy": { "http": { "host": "proxy.example.com", "port": "80" } } } }'

Settings for an HTTPS proxy are set in the git.proxy.https object. These might be set as shown in the following command:

cf create-service p.config-server standard config-server -c '{"git": { "proxy": { "https": { "host": "secure.example.com", "port": "443" } } } }'

Note: Some networks require that separate proxy servers are used for HTTP and HTTPS URLs. In such a case, you can set both the proxy.http and proxy.https objects.

The parameters used to configure HTTP or HTTPS proxy settings for the Config Server are listed below.

Parameter Function
proxy.http A proxy object, containing HTTP proxy fields
proxy.http.host The HTTP proxy host
proxy.http.port The HTTP proxy port
proxy.http.nonProxyHosts The hosts to access outside the HTTP proxy
proxy.http.username The username to use with an authenticated HTTP proxy
proxy.http.password The password to use with an authenticated HTTP proxy
proxy.https A proxy object, containing HTTPS proxy fields
proxy.https.host The HTTPS proxy host
proxy.https.port The HTTPS proxy port
proxy.https.nonProxyHosts The hosts to access outside the HTTPS proxy (if proxy.http.nonProxyHosts is also provided, http.nonProxyHosts will be used instead of https.nonProxyHosts)
proxy.https.username The username to use with an authenticated HTTPS proxy (if proxy.http.username is also provided, http.username will be used instead of https.username)
proxy.https.password The password to use with an authenticated HTTPS proxy (if proxy.http.password is also provided, http.password will be used instead of https.password)

To configure a Config Server service instance that uses an HTTP proxy to access configuration sources, use the following command:

cf create-service p.config-server standard config-server -c '{"git": {"uri": "https://github.com/spring-cloud-services-samples/cook-config", "proxy": { "http": { "host": "proxy.example.com", "port": "80" } } } }'

To configure a Config Server service instance that uses an authenticated HTTPS proxy to access configuration sources, specifying that example.com should be accessed outside of the proxy, use the following command:

cf create-service p.config-server standard config-server -c '{"git": {"uri": "https://github.com/spring-cloud-services-samples/cook-config", "proxy": { "https": { "host": "secure.example.com", "port": "443", "username": "jim", "password": "wright62", "nonProxyHosts": "example.com" } } } }'