Spring Cloud Config provides server and client-side support for externalized configuration in a distributed system. With the Config Server you have a central place to manage external properties for applications across all environments. The concepts on both client and server map identically to the Spring Environment
and PropertySource
abstractions, so they fit very well with Spring applications, but can be used with any application running in any language. As an application moves through the deployment pipeline from dev to test and into production you can manage the configuration between those environments and be certain that applications have everything they need to run when they migrate. The default implementation of the server storage backend uses git so it easily supports labelled versions of configuration environments, as well as being accessible to a wide range of tooling for managing the content. It is easy to add alternative implementations and plug them in with Spring configuration.
Quick Start
Start the server:
$ cd spring-cloud-config-server $ ../mvnw spring-boot:run
The server is a Spring Boot application so you can run it from your
IDE instead if you prefer (the main class is
ConfigServerApplication
). Then try out a client:
$ curl localhost:8888/foo/development {"name":"development","label":"master","propertySources":[ {"name":"https://github.com/scratches/config-repo/foo-development.properties","source":{"bar":"spam"}}, {"name":"https://github.com/scratches/config-repo/foo.properties","source":{"foo":"bar"}} ]}
The default strategy for locating property sources is to clone a git
repository (at spring.cloud.config.server.git.uri
) and use it to
initialize a mini SpringApplication
. The mini-application’s
Environment
is used to enumerate property sources and publish them
via a JSON endpoint.
The HTTP service has resources in the form:
/{application}/{profile}[/{label}] /{application}-{profile}.yml /{label}/{application}-{profile}.yml /{application}-{profile}.properties /{label}/{application}-{profile}.properties
where the "application" is injected as the spring.config.name
in the
SpringApplication
(i.e. what is normally "application" in a regular
Spring Boot app), "profile" is an active profile (or comma-separated
list of properties), and "label" is an optional git label (defaults to
"master".)
Spring Cloud Config Server pulls configuration for remote clients from a git repository (which must be provided):
spring:
cloud:
config:
server:
git:
uri: https://github.com/spring-cloud-samples/config-repo
Client Side Usage
To use these features in an application, just build it as a Spring
Boot application that depends on spring-cloud-config-client (e.g. see
the test cases for the config-client, or the sample app). The most
convenient way to add the dependency is via a Spring Boot starter
org.springframework.cloud:spring-cloud-starter-config
. There is also a
parent pom and BOM (spring-cloud-starter-parent
) for Maven users and a
Spring IO version management properties file for Gradle and Spring CLI
users. Example Maven configuration:
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.3.5.RELEASE</version>
<relativePath /> <!-- lookup parent from repository -->
</parent>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>Brixton.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-config</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
<!-- repositories also needed for snapshots and milestones -->
Then you can create a standard Spring Boot application, like this simple HTTP server:
@SpringBootApplication @RestController public class Application { @RequestMapping("/") public String home() { return "Hello World!"; } public static void main(String[] args) { SpringApplication.run(Application.class, args); } }
When it runs it will pick up the external configuration from the
default local config server on port 8888 if it is running. To modify
the startup behaviour you can change the location of the config server
using bootstrap.properties
(like application.properties
but for
the bootstrap phase of an application context), e.g.
spring.cloud.config.uri: http://myconfigserver.com
The bootstrap properties will show up in the /env
endpoint as a
high-priority property source, e.g.
$ curl localhost:8080/env { "profiles":[], "configService:https://github.com/spring-cloud-samples/config-repo/bar.properties":{"foo":"bar"}, "servletContextInitParams":{}, "systemProperties":{...}, ... }
(a property source called "configService:<URL of remote repository>/<file name>" contains the property "foo" with value "bar" and is highest priority).
Note
|
the URL in the property source name is the git repository not the config server URL. |
Spring Cloud Config Server
The Server provides an HTTP, resource-based API for external
configuration (name-value pairs, or equivalent YAML content). The
server is easily embeddable in a Spring Boot application using the
@EnableConfigServer
annotation. So this app is a config server:
@SpringBootApplication
@EnableConfigServer
public class ConfigServer {
public static void main(String[] args) {
SpringApplication.run(ConfigServer.class, args);
}
}
Like all Spring Boot apps it runs on port 8080 by default, but you
can switch it to the conventional port 8888 in various ways. The
easiest, which also sets a default configuration repository,
is by launching it with spring.config.name=configserver
(there
is a configserver.yml
in the Config Server jar). Another is
to use your own application.properties
, e.g.
server.port: 8888
spring.cloud.config.server.git.uri: file://${user.home}/config-repo
where ${user.home}/config-repo
is a git repository containing
YAML and properties files.
Note
|
in Windows you need an extra "/" in the file URL if it is
absolute with a drive prefix, e.g. file:///${user.home}/config-repo .
|
Tip
|
Here’s a recipe for creating the git repository in the example above: $ cd $HOME $ mkdir config-repo $ cd config-repo $ git init . $ echo info.foo: bar > application.properties $ git add -A . $ git commit -m "Add application.properties" |
Warning
|
using the local filesystem for your git repository is intended for testing only. Use a server to host your configuration repositories in production. |
Warning
|
the initial clone of your configuration repository will be quick and efficient if you only keep text files in it. If you start to store binary files, especially large ones, you may experience delays on the first request for configuration and/or out of memory errors in the server. |
Environment Repository
Where do you want to store the configuration data for the Config
Server? The strategy that governs this behaviour is the
EnvironmentRepository
, serving Environment
objects. This
Environment
is a shallow copy of the domain from the Spring
Environment
(including propertySources
as the main feature). The
Environment
resources are parametrized by three variables:
-
{application}
maps to "spring.application.name" on the client side; -
{profile}
maps to "spring.profiles.active" on the client (comma separated list); and -
{label}
which is a server side feature labelling a "versioned" set of config files.
Repository implementations generally behave just like a Spring Boot
application loading configuration files from a "spring.config.name"
equal to the {application}
parameter, and "spring.profiles.active"
equal to the {profiles}
parameter. Precedence rules for profiles are
also the same as in a regular Boot application: active profiles take
precedence over defaults, and if there are multiple profiles the last
one wins (like adding entries to a Map
).
Example: a client application has this bootstrap configuration:
spring:
application:
name: foo
profiles:
active: dev,mysql
(as usual with a Spring Boot application, these properties could also be set as environment variables or command line arguments).
If the repository is file-based, the server will create an
Environment
from application.yml
(shared between all clients), and
foo.yml
(with foo.yml
taking precedence). If the YAML files have
documents inside them that point to Spring profiles, those are applied
with higher precedence (in order of the profiles listed), and if
there are profile-specific YAML (or properties) files these are also
applied with higher precedence than the defaults. Higher precedence
translates to a PropertySource
listed earlier in the
Environment
. (These are the same rules as apply in a standalone
Spring Boot application.)
Git Backend
The default implementation of EnvironmentRepository
uses a Git
backend, which is very convenient for managing upgrades and physical
environments, and also for auditing changes. To change the location of
the repository you can set the "spring.cloud.config.server.git.uri"
configuration property in the Config Server (e.g. in
application.yml
). If you set it with a file:
prefix it should work
from a local repository so you can get started quickly and easily
without a server, but in that case the server operates directly on the
local repository without cloning it (it doesn’t matter if it’s not
bare because the Config Server never makes changes to the "remote"
repository). To scale the Config Server up and make it highly
available, you would need to have all instances of the server pointing
to the same repository, so only a shared file system would work. Even
in that case it is better to use the ssh:
protocol for a shared
filesystem repository, so that the server can clone it and use a local
working copy as a cache.
This repository implementation maps the {label}
parameter of the
HTTP resource to a git label (commit id, branch name or tag). If the
git branch or tag name contains a slash ("/") then the label in the
HTTP URL should be specified with the special string "(_)" instead (to
avoid ambiguity with other URL paths). Be careful with the brackets in
the URL if you are using a command line client like curl (e.g. escape
them from the shell with quotes '').
Placeholders in Git URI
Spring Cloud Config Server supports a git repository URL with
placeholders for the {application}
and {profile}
(and {label}
if
you need it, but remember that the label is applied as a git label
anyway). So you can easily support a "one repo per application" policy
using (for example):
spring:
cloud:
config:
server:
git:
uri: https://github.com/myorg/{application}
or a "one repo per profile" policy using a similar pattern but with
{profile}
.
Pattern Matching and Multiple Repositories
There is also support for more complex requirements with pattern
matching on the application and profile name. The pattern format is a
comma-separated list of {application}/{profile}
names with wildcards
(where a pattern beginning with a wildcard may need to be
quoted). Example:
spring:
cloud:
config:
server:
git:
uri: https://github.com/spring-cloud-samples/config-repo
repos:
simple: https://github.com/simple/config-repo
special:
pattern: special*/dev*,*special*/dev*
uri: https://github.com/special/config-repo
local:
pattern: local*
uri: file:/home/configsvc/config-repo
If {application}/{profile}
does not match any of the patterns, it
will use the default uri defined under
"spring.cloud.config.server.git.uri". In the above example, for the
"simple" repository, the pattern is simple/*
(i.e. it only matches
one application named "simple" in all profiles). The "local"
repository matches all application names beginning with "local" in all
profiles (the /*
suffix is added automatically to any pattern that
doesn’t have a profile matcher).
Note
|
the "one-liner" short cut used in the "simple" example above can only be used if the only property to be set is the URI. If you need to set anything else (credentials, pattern, etc.) you need to use the full form. |
The pattern
property in the repo is actually an array, so you can
use a YAML array (or [0]
, [1]
, etc. suffixes in properties files)
to bind to multiple patterns. You may need to do this if you are going
to run apps with multiple profiles. Example:
spring:
cloud:
config:
server:
git:
uri: https://github.com/spring-cloud-samples/config-repo
repos:
development:
pattern:
- */development
- */staging
uri: https://github.com/development/config-repo
staging:
pattern:
- */qa
- */production
uri: https://github.com/staging/config-repo
Note
|
Spring Cloud will guess that a pattern containing a profile that
doesn’t end in * implies that you actually want to match a list of
profiles starting with this pattern (so */staging is a shortcut for
["*/staging", "*/staging,*"] ). This is common where you need to run
apps in the "development" profile locally but also the "cloud" profile
remotely, for instance.
|
Every repository can also optionally store config files in
sub-directories, and patterns to search for those directories can be
specified as searchPaths
. For example at the top level:
spring:
cloud:
config:
server:
git:
uri: https://github.com/spring-cloud-samples/config-repo
searchPaths: foo,bar*
In this example the server searches for config files in the top level and in the "foo/" sub-directory and also any sub-directory whose name begins with "bar".
By default the server clones remote repositories when configuration is first requested. The server can be configured to clone the repositories at startup. For example at the top level:
spring:
cloud:
config:
server:
git:
uri: https://git/common/config-repo.git
repos:
team-a:
pattern: team-a-*
cloneOnStart: true
uri: http://git/team-a/config-repo.git
team-b:
pattern: team-b-*
cloneOnStart: false
uri: http://git/team-b/config-repo.git
team-c:
pattern: team-c-*
uri: http://git/team-a/config-repo.git
In this example the server clones team-a’s config-repo on startup before it accepts any requests. All other repositories will not be cloned until configuration from the repository is requested.
Note
|
Setting a repository to be cloned when the Config Server starts up can
help to identify a misconfigured configuration source (e.g., an invalid
repository URI) quickly, while the Config Server is starting up. With
cloneOnStart not enabled for a configuration source, the Config Server may
start successfully with a misconfigured or invalid configuration source and
not log an error until an application requests configuration from that
configuration source.
|
To use HTTP basic authentication on the remote repository add the "username" and "password" properties separately (not in the URL), e.g.
spring:
cloud:
config:
server:
git:
uri: https://github.com/spring-cloud-samples/config-repo
username: trolley
password: strongpassword
If you don’t use HTTPS and user credentials, SSH should also work out
of the box when you store keys in the default directories (~/.ssh
)
and the uri points to an SSH location,
e.g. "[email protected]:configuration/cloud-configuration". It is important that all
keys in ~/.ssh/known_hosts are in "ssh-rsa" format. The new "ecdsa-sha2-nistp256" format is NOT supported.
The repository is accessed using JGit, so any documentation you find on
that should be applicable. HTTPS proxy settings can be set in
~/.git/config
or in the same way as for any other JVM process via
system properties (-Dhttps.proxyHost
and -Dhttps.proxyPort
).
Tip
|
If you don’t know where your ~/.git directory is us git config
--global to manipulate the settings (e.g. git config --global
http.sslVerify false ).
|
Placeholders in Git Search Paths
Spring Cloud Config Server also supports a search path with
placeholders for the {application}
and {profile}
(and {label}
if
you need it). Example:
spring:
cloud:
config:
server:
git:
uri: https://github.com/spring-cloud-samples/config-repo
searchPaths: '{application}'
searches the repository for files in the same name as the directory (as well as the top level). Wildcards are also valid in a search path with placeholders (any matching directory is included in the search).
Version Control Backend Filesystem Use
Warning
|
With VCS based backends (git, svn) files are checked out or cloned to the local filesystem. By default they are put in the system temporary directory with a prefix of config-repo- . On linux, for example it could be /tmp/config-repo-<randomid> . Some operating systems routinely clean out temporary directories. This can lead to unexpected behaviour such as missing properties. To avoid this problem, change the directory Config Server uses, by setting spring.cloud.config.server.git.basedir or spring.cloud.config.server.svn.basedir to a directory that does not reside in the system temp structure.
|
File System Backend
There is also a "native" profile in the Config Server that doesn’t use Git, but just loads the config files from the local classpath or file system (any static URL you want to point to with "spring.cloud.config.server.native.searchLocations"). To use the native profile just launch the Config Server with "spring.profiles.active=native".
Note
|
Remember to use the file: prefix for file resources (the
default without a prefix is usually the classpath). Just as with any
Spring Boot configuration you can embed ${} -style environment
placeholders, but remember that absolute paths in Windows require an
extra "/", e.g. file:///${user.home}/config-repo
|
Warning
|
The default value of the searchLocations is identical to a
local Spring Boot application (so [classpath:/, classpath:/config,
file:./, file:./config] ). This does not expose the
application.properties from the server to all clients because any
property sources present in the server are removed before being sent
to the client.
|
Tip
|
A filesystem backend is great for getting started quickly and for testing. To use it in production you need to be sure that the file system is reliable, and shared across all instances of the Config Server. |
The search locations can contain placeholders for {application}
,
{profile}
and {label}
. In this way you can segregate the
directories in the path, and choose a strategy that makes sense for
you (e.g. sub-directory per application, or sub-directory per
profile).
If you don’t use placeholders in the search locations, this repository
also appends the {label}
parameter of the HTTP resource to a suffix
on the search path, so properties files are loaded from each search
location and a subdirectory with the same name as the label (the
labelled properties take precedence in the Spring Environment). Thus
the default behaviour with no placeholders is the same as adding a
search location ending with /{label}/. For example `file:/tmp/config
is the same as file:/tmp/config,file:/tmp/config/{label}
Vault Backend
Spring Cloud Config Server also supports Vault as a backend.
For more information on Vault see the Vault quickstart guide.
To enable the config server to use a Vault backend you must run your config server
with the vault
profile. For example in your config server’s application.properties
you can add spring.profiles.active=vault
.
By default the config server will assume your Vault server is running at
http://127.0.0.1:8200
. It also will assume that the name of backend
is secret
and the key is application
. All of these defaults can be
configured in your config server’s application.properties
. Below is a
table of configurable Vault properties. All properties are prefixed with
spring.cloud.config.server.vault
.
Name | Default Value |
---|---|
host |
127.0.0.1 |
port |
8200 |
scheme |
http |
backend |
secret |
defaultKey |
application |
profileSeparator |
, |
All configurable properties can be found in
org.springframework.cloud.config.server.environment.VaultEnvironmentRepository
.
With your config server running you can make HTTP requests to the server to retrieve values from the Vault backend. To do this you will need a token for your Vault server.
First place some data in you Vault. For example
$ vault write secret/application foo=bar baz=bam
$ vault write secret/myapp foo=myappsbar
Now make the HTTP request to your config server to retrieve the values.
$ curl -X "GET" "http://localhost:8888/myapp/default" -H "X-Config-Token: yourtoken"
You should see a response similar to this after making the above request.
{
"name":"myapp",
"profiles":[
"default"
],
"label":null,
"version":null,
"state":null,
"propertySources":[
{
"name":"vault:myapp",
"source":{
"foo":"myappsbar"
}
},
{
"name":"vault:application",
"source":{
"baz":"bam",
"foo":"bar"
}
}
]
}
Multiple Properties Sources
When using Vault you can provide your applications with multiple properties sources. For example, assume you have written data to the following paths in Vault.
secret/myApp,dev
secret/myApp
secret/application,dev
secret/application
Properties written to secret/application
are available to
all applications using the Config Server. An
application with the name myApp
would have any properties
written to secret/myApp
and secret/application
available to it.
When myApp
has the dev
profile enabled than properties written to
all of the above paths would be available to it, with properties in
the first path in the list taking priority over the others.
Sharing Configuration With All Applications
File Based Repositories
With file-based (i.e. git, svn and native) repositories, resources
with file names in application*
are shared between all client
applications (so application.properties
, application.yml
,
application-*.properties
etc.). You can use resources with these
file names to configure global defaults and have them overridden by
application-specific files as necessary.
The #_property_overrides[property overrides] feature can also be used for setting global defaults, and with placeholders applications are allowed to override them locally.
Tip
|
With the "native" profile (local file system backend) it is
recommended that you use an explicit search location that isn’t part
of the server’s own configuration. Otherwise the application*
resources in the default search locations are removed because they are
part of the server.
|
Vault Server
When using Vault as a backend you can share configuration with
all applications by placing configuration in
html5/application
. For example, if you run this Vault command
$ vault write secret/application foo=bar baz=bam
All applications using the config server will have the properties
foo
and baz
available to them.
Property Overrides
The Config Server has an "overrides" feature that allows the operator
to provide configuration properties to all applications that cannot be
accidentally changed by the application using the normal Spring Boot
hooks. To declare overrides just add a map of name-value pairs to
spring.cloud.config.server.overrides
. For example
spring:
cloud:
config:
server:
overrides:
foo: bar
will cause all applications that are config clients to read foo=bar
independent of their own configuration. (Of course an application can
use the data in the Config Server in any way it likes, so overrides
are not enforceable, but they do provide useful default behaviour if
they are Spring Cloud Config clients.)
Tip
|
Normal, Spring environment placeholders with "${}" can be escaped
(and resolved on the client) by using backslash ("\") to escape the
"$" or the "{", e.g. \${app.foo:bar} resolves to "bar" unless the
app provides its own "app.foo". Note that in YAML you don’t need to
escape the backslash itself, but in properties files you do, when you
configure the overrides on the server.
|
You can change the priority of all overrides in the client to be more
like default values, allowing applications to supply their own values
in environment variables or System properties, by setting the flag
spring.cloud.config.overrideNone=true
(default is false) in the
remote repository.
Health Indicator
Config Server comes with a Health Indicator that checks if the configured
EnvironmentRepository
is working. By default it asks the EnvironmentRepository
for an application named app
, the default
profile and the default
label provided by the EnvironmentRepository
implementation.
You can configure the Health Indicator to check more applications along with custom profiles and custom labels, e.g.
spring:
cloud:
config:
server:
health:
repositories:
myservice:
label: mylabel
myservice-dev:
name: myservice
profiles: development
You can disable the Health Indicator by setting spring.cloud.config.server.health.enabled=false
.
Security
You are free to secure your Config Server in any way that makes sense to you (from physical network security to OAuth2 bearer tokens), and Spring Security and Spring Boot make it easy to do pretty much anything.
To use the default Spring Boot configured HTTP Basic security, just
include Spring Security on the classpath (e.g. through
spring-boot-starter-security
). The default is a username of "user"
and a randomly generated password, which isn’t going to be very useful
in practice, so we recommend you configure the password (via
security.user.password
) and encrypt it (see below for instructions
on how to do that).
Encryption and Decryption
Important
|
Prerequisites: to use the encryption and decryption features you need the full-strength JCE installed in your JVM (it’s not there by default). You can download the "Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files" from Oracle, and follow instructions for installation (essentially replace the 2 policy files in the JRE lib/security directory with the ones that you downloaded). |
If the remote property sources contain encrypted content (values
starting with {cipher}
) they will be decrypted before sending to
clients over HTTP. The main advantage of this set up is that the
property values don’t have to be in plain text when they are "at rest"
(e.g. in a git repository). If a value cannot be decrypted it is
removed from the property source and an additional property is added
with the same key, but prefixed with "invalid." and a value that means
"not applicable" (usually "<n/a>"). This is largely to prevent cipher
text being used as a password and accidentally leaking.
If you are setting up a remote config repository for config client
applications it might contain an application.yml
like this, for
instance:
spring:
datasource:
username: dbuser
password: '{cipher}FKSAJDFGYOS8F7GLHAKERGFHLSAJ'
Encrypted values in a .properties file must not be wrapped in quotes, otherwise the value will not be decrypted:
spring.datasource.username: dbuser spring.datasource.password: {cipher}FKSAJDFGYOS8F7GLHAKERGFHLSAJ
You can safely push this plain text to a shared git repository and the secret password is protected.
The server also exposes /encrypt
and /decrypt
endpoints (on the
assumption that these will be secured and only accessed by authorized
agents). If you are editing a remote config file you can use the Config Server
to encrypt values by POSTing to the /encrypt
endpoint, e.g.
$ curl localhost:8888/encrypt -d mysecret 682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda
The inverse operation is also available via /decrypt
(provided the server is
configured with a symmetric key or a full key pair):
$ curl localhost:8888/decrypt -d 682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda mysecret
Tip
|
If you are testing like this with curl, then use
--data-urlencode (instead of -d ) or set an explicit Content-Type:
text/plain to make sure curl encodes the data correctly when there
are special characters ('+' is particularly tricky).
|
Take the encrypted value and add the {cipher}
prefix before you put
it in the YAML or properties file, and before you commit and push it
to a remote, potentially insecure store.
The /encrypt
and /decrypt
endpoints also both accept paths of the
form /*/{name}/{profiles}
which can be used to control cryptography
per application (name) and profile when clients call into the main
Environment resource.
Note
|
to control the cryptography in this granular way you must also
provide a @Bean of type TextEncryptorLocator that creates a
different encryptor per name and profiles. The one that is provided
by default does not do this (so all encryptions use the same key).
|
The spring
command line client (with Spring Cloud CLI extensions
installed) can also be used to encrypt and decrypt, e.g.
$ spring encrypt mysecret --key foo 682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda $ spring decrypt --key foo 682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda mysecret
To use a key in a file (e.g. an RSA public key for encryption) prepend the key value with "@" and provide the file path, e.g.
$ spring encrypt mysecret --key @${HOME}/.ssh/id_rsa.pub AQAjPgt3eFZQXwt8tsHAVv/QHiY5sI2dRcR+...
The key argument is mandatory (despite having a --
prefix).
Key Management
The Config Server can use a symmetric (shared) key or an asymmetric one (RSA key pair). The asymmetric choice is superior in terms of security, but it is often more convenient to use a symmetric key since it is just a single property value to configure.
To configure a symmetric key you just need to set encrypt.key
to a
secret String (or use an enviroment variable ENCRYPT_KEY
to keep it
out of plain text configuration files).
To configure an asymmetric key you can either set the key as a
PEM-encoded text value (in encrypt.key
), or via a keystore (e.g. as
created by the keytool
utility that comes with the JDK). The
keystore properties are encrypt.keyStore.*
with *
equal to
-
location
(aResource
location), -
password
(to unlock the keystore) and -
alias
(to identify which key in the store is to be used).
The encryption is done with the public key, and a private key is needed for decryption. Thus in principle you can configure only the public key in the server if you only want to do encryption (and are prepared to decrypt the values yourself locally with the private key). In practice you might not want to do that because it spreads the key management process around all the clients, instead of concentrating it in the server. On the other hand it’s a useful option if your config server really is relatively insecure and only a handful of clients need the encrypted properties.
Creating a Key Store for Testing
To create a keystore for testing you can do something like this:
$ keytool -genkeypair -alias mytestkey -keyalg RSA \ -dname "CN=Web Server,OU=Unit,O=Organization,L=City,S=State,C=US" \ -keypass changeme -keystore server.jks -storepass letmein
Put the server.jks
file in the classpath (for instance) and then in
your application.yml
for the Config Server:
encrypt:
keyStore:
location: classpath:/server.jks
password: letmein
alias: mytestkey
secret: changeme
Using Multiple Keys and Key Rotation
In addition to the {cipher}
prefix in encrypted property values, the
Config Server looks for {name:value}
prefixes (zero or many) before
the start of the (Base64 encoded) cipher text. The keys are passed to
a TextEncryptorLocator
which can do whatever logic it needs to
locate a TextEncryptor
for the cipher. If you have configured a
keystore (encrypt.keystore.location
) the default locator will look
for keys in the store with aliases as supplied by the "key" prefix,
i.e. with a cipher text like this:
foo:
bar: `{cipher}{key:testkey}...`
the locator will look for a key named "testkey". A secret can also be
supplied via a {secret:…}
value in the prefix, but if it is not
the default is to use the keystore password (which is what you get
when you build a keytore and don’t specify a secret). If you do
supply a secret it is recommended that you also encrypt the secrets
using a custom SecretLocator
.
Key rotation is hardly ever necessary on cryptographic grounds if the
keys are only being used to encrypt a few bytes of configuration data
(i.e. they are not being used elsewhere), but occasionally you might
need to change the keys if there is a security breach for instance. In
that case all the clients would need to change their source config
files (e.g. in git) and use a new {key:…}
prefix in all the
ciphers, checking beforehand of course that the key alias is available
in the Config Server keystore.
Tip
|
the {name:value} prefixes can also be added to plaintext posted
to the /encrypt endpoint, if you want to let the Config Server
handle all encryption as well as decryption.
|
Serving Encrypted Properties
Sometimes you want the clients to decrypt the configuration locally,
instead of doing it in the server. In that case you can still have
/encrypt and /decrypt endpoints (if you provide the encrypt.*
configuration to locate a key), but you need to explicitly switch off
the decryption of outgoing properties using
spring.cloud.config.server.encrypt.enabled=false
. If you don’t care
about the endpoints, then it should work if you configure neither the
key nor the enabled flag.
Serving Alternative Formats
The default JSON format from the environment endpoints is perfect for
consumption by Spring applications because it maps directly onto the
Environment
abstraction. If you prefer you can consume the same data
as YAML or Java properties by adding a suffix to the resource path
(".yml", ".yaml" or ".properties"). This can be useful for consumption
by applications that do not care about the structure of the JSON
endpoints, or the extra metadata they provide, for example an
application that is not using Spring might benefit from the simplicity
of this approach.
The YAML and properties representations have an additional flag
(provided as a boolean query parameter resolvePlaceholders
) to
signal that placeholders in the source documents, in the standard
Spring ${…}
form, should be resolved in the output where possible
before rendering. This is a useful feature for consumers that don’t
know about the Spring placeholder conventions.
Note
|
there are limitations in using the YAML or properties formats, mainly in relation to the loss of metadata. The JSON is structured as an ordered list of property sources, for example, with names that correlate with the source. The YAML and properties forms are coalesced into a single map, even if the origin of the values has multiple sources, and the names of the original source files are lost. The YAML representation is not necessarily a faithful representation of the YAML source in a backing repository either: it is constructed from a list of flat property sources, and assumptions have to be made about the form of the keys. |
Serving Plain Text
Instead of using the Environment
abstraction (or one of the
alternative representations of it in YAML or properties format) your
applications might need generic plain text configuration files,
tailored to their environment. The Config Server provides these
through an additional endpoint at /{name}/{profile}/{label}/{path}
where "name", "profile" and "label" have the same meaning as the
regular environment endpoint, but "path" is a file name
(e.g. log.xml
). The source files for this endpoint are located in
the same way as for the environment endpoints: the same search path is
used as for properties or YAML files, but instead of aggregating all
matching resources, only the first one to match is returned.
After a resource is located, placeholders in the normal format
(${…}
) are resolved using the effective Environment
for the
application name, profile and label supplied. In this way the resource
endpoint is tightly integrated with the environment
endpoints. Example, if you have this layout for a GIT (or SVN)
repository:
application.yml nginx.conf
where nginx.conf
looks like this:
server { listen 80; server_name ${nginx.server.name}; }
and application.yml
like this:
nginx:
server:
name: example.com
---
spring:
profiles: development
nginx:
server:
name: develop.com
then the /foo/default/master/nginx.conf
resource looks like this:
server { listen 80; server_name example.com; }
and /foo/development/master/nginx.conf
like this:
server { listen 80; server_name develop.com; }
Note
|
just like the source files for environment configuration, the
"profile" is used to resolve the file name, so if you want a
profile-specific file then /*/development/*/logback.xml will be
resolved by a file called logback-development.xml (in preference
to logback.xml ).
|
Embedding the Config Server
The Config Server runs best as a standalone application, but if you
need to you can embed it in another application. Just use the
@EnableConfigServer
annotation. An optional property that can be
useful in this case is spring.cloud.config.server.bootstrap
which is
a flag to indicate that the server should configure itself from its
own remote repository. The flag is off by default because it can delay
startup, but when embedded in another application it makes sense to
initialize the same way as any other application.
Note
|
It should be obvious, but remember that if you use the bootstrap
flag the config server will need to have its name and repository URI
configured in bootstrap.yml .
|
To change the location of the server endpoints you can (optionally)
set spring.cloud.config.server.prefix
, e.g. "/config", to serve the
resources under a prefix. The prefix should start but not end with a
"/". It is applied to the @RequestMappings
in the Config Server
(i.e. underneath the Spring Boot prefixes server.servletPath
and
server.contextPath
).
If you want to read the configuration for an application directly from
the backend repository (instead of from the config server) that’s
basically an embedded config server with no endpoints. You can switch
off the endpoints entirely if you don’t use the @EnableConfigServer
annotation (just set spring.cloud.config.server.bootstrap=true
).
Push Notifications and Spring Cloud Bus
Many source code repository providers (like Github, Gitlab or Bitbucket
for instance) will notify you of changes in a repository through a
webhook. You can configure the webhook via the provider’s user
interface as a URL and a set of events in which you are
interested. For instance
Github
will POST to the webhook with a JSON body containing a list of
commits, and a header "X-Github-Event" equal to "push". If you add a
dependency on the spring-cloud-config-monitor
library and activate
the Spring Cloud Bus in your Config Server, then a "/monitor" endpoint
is enabled.
When the webhook is activated the Config Server will send a
RefreshRemoteApplicationEvent
targeted at the applications it thinks
might have changed. The change detection can be strategized, but by
default it just looks for changes in files that match the application
name (e.g. "foo.properties" is targeted at the "foo" application, and
"application.properties" is targeted at all applications). The strategy
if you want to override the behaviour is PropertyPathNotificationExtractor
which accepts the request headers and body as parameters and returns a list
of file paths that changed.
The default configuration works out of the box with Github, Gitlab or
Bitbucket. In addition to the JSON notifications from Github, Gitlab
or Bitbucket you can trigger a change notification by POSTing to
"/monitor" with a form-encoded body parameters path={name}
. This will
broadcast to applications matching the "{name}" pattern (can contain
wildcards).
Note
|
the RefreshRemoteApplicationEvent will only be transmitted if
the spring-cloud-bus is activated in the Config Server and in the
client application.
|
Note
|
the default configuration also detects filesystem changes in local git repositories (the webhook is not used in that case but as soon as you edit a config file a refresh will be broadcast). |
Spring Cloud Config Client
A Spring Boot application can take immediate advantage of the Spring
Config Server (or other external property sources provided by the
application developer), and it will also pick up some additional
useful features related to Environment
change events.
Config First Bootstrap
This is the default behaviour for any application which has the Spring
Cloud Config Client on the classpath. When a config client starts up
it binds to the Config Server (via the bootstrap configuration
property spring.cloud.config.uri
) and initializes Spring
Environment
with remote property sources.
The net result of this is that all client apps that want to consume
the Config Server need a bootstrap.yml
(or an environment variable)
with the server address in spring.cloud.config.uri
(defaults to
"http://localhost:8888").
Discovery First Bootstrap
If you are using a `DiscoveryClient implementation, such as Spring Cloud Netflix and Eureka Service Discovery or Spring Cloud Consul (Spring Cloud Zookeeper does not support this yet), then you can have the Config Server register with the Discovery Service if you want to, but in the default "Config First" mode, clients won’t be able to take advantage of the registration.
If you prefer to use DiscoveryClient
to locate the Config Server, you can do
that by setting spring.cloud.config.discovery.enabled=true
(default
"false"). The net result of that is that client apps all need a
bootstrap.yml
(or an environment variable) with the appropriate discovery
configuration. For example, with Spring Cloud Netflix, you need to define the
Eureka server address, e.g. in eureka.client.serviceUrl.defaultZone
. The
price for using this option is an extra network round trip on start up to
locate the service registration. The benefit is that the Config Server
can change its co-ordinates, as long as the Discovery Service is a fixed point. The
default service id is "configserver" but you can change that on the
client with spring.cloud.config.discovery.serviceId
(and on the server
in the usual way for a service, e.g. by setting spring.application.name
).
The discovery client implementations all support some kind of metadata
map (e.g. for Eureka we have eureka.instance.metadataMap
). Some
additional properties of the Config Server may need to be configured
in its service registration metadata so that clients can connect
correctly. If the Config Server is secured with HTTP Basic you can
configure the credentials as "username" and "password". And if the
Config Server has a context path you can set "configPath". Example,
for a Config Server that is a Eureka client:
eureka:
instance:
...
metadataMap:
user: osufhalskjrtl
password: lviuhlszvaorhvlo5847
configPath: /config
Config Client Fail Fast
In some cases, it may be desirable to fail startup of a service if
it cannot connect to the Config Server. If this is the desired
behavior, set the bootstrap configuration property
spring.cloud.config.failFast=true
and the client will halt with
an Exception.
Config Client Retry
If you expect that the config server may occasionally be unavailable when
your app starts, you can ask it to keep trying after a failure. First you need
to set spring.cloud.config.failFast=true
, and then you need to add
spring-retry
and spring-boot-starter-aop
to your classpath. The default
behaviour is to retry 6 times with an initial backoff interval of 1000ms and an
exponential multiplier of 1.1 for subsequent backoffs. You can configure these
properties (and others) using spring.cloud.config.retry.*
configuration properties.
Tip
|
To take full control of the retry add a @Bean of type
RetryOperationsInterceptor with id "configServerRetryInterceptor". Spring
Retry has a RetryInterceptorBuilder that makes it easy to create one.
|
Locating Remote Configuration Resources
The Config Service serves property sources from /{name}/{profile}/{label}
, where the default bindings in the client app are
-
"name" =
${spring.application.name}
-
"profile" =
${spring.profiles.active}
(actuallyEnvironment.getActiveProfiles()
) -
"label" = "master"
All of them can be overridden by setting spring.cloud.config.*
(where *
is "name", "profile" or "label"). The "label" is useful for
rolling back to previous versions of configuration; with the default
Config Server implementation it can be a git label, branch name or
commit id. Label can also be provided as a comma-separated list, in
which case the items in the list are tried on-by-one until one succeeds.
This can be useful when working on a feature branch, for instance,
when you might want to align the config label with your branch, but
make it optional (e.g. spring.cloud.config.label=myfeature,develop
).
Security
If you use HTTP Basic security on the server then clients just need to know the password (and username if it isn’t the default). You can do that via the config server URI, or via separate username and password properties, e.g.
spring:
cloud:
config:
uri: https://user:[email protected]
or
spring:
cloud:
config:
uri: https://myconfig.mycompany.com
username: user
password: secret
The spring.cloud.config.password
and spring.cloud.config.username
values override anything that is provided in the URI.
If you deploy your apps on Cloud Foundry then the best way to provide the password is through service credentials, e.g. in the URI, since then it doesn’t even need to be in a config file. An example which works locally and for a user-provided service on Cloud Foundry named "configserver":
spring:
cloud:
config:
uri: ${vcap.services.configserver.credentials.uri:http://user:password@localhost:8888}
If you use another form of security you might need to provide a
RestTemplate
to the ConfigServicePropertySourceLocator
(e.g. by
grabbing it in the bootstrap context and injecting one).
Vault
When using Vault as a backend to your config server the client will need to
supply a token for the server to retrieve values from Vault. This token
can be provided within the client by setting spring.cloud.config.token
in bootstrap.yml
.
spring:
cloud:
config:
token: YourVaultToken
Vault
Nested Keys In Vault
Vault supports the ability to nest keys in a value stored in Vault. For example
echo -n '{"appA": {"secret": "appAsecret"}, "bar": "baz"}' | vault write secret/myapp -
This command will write a JSON object to your Vault. To access these values in Spring you would use the traditional dot(.) annotation. For example
@Value("${appA.secret}")
String name = "World";
The above code would set the name
variable to appAsecret
.