config server cache properties for same client and force refresh by git webhook

[jacobke]

Hi, i adopt spring cloud config server as my configuration management center.
There are 50+ applications and they ask config server for latest properties at the interval of 1 minute (we want they could notice the changes ASAP).

Then the problem is that config server would pull git frequently (it seems config server pull git per request). This make our git server quite busy.

So could we make config server *cache * properties for same client (by its application name and profile)? If we need force refresh the cache, we could add git webhook to trigger that.
(git webhook function seems added in spring-cloud-config-monitor project, but not designed for this kind of features)

I'm not quite deep into config server codes, If there is misuse or better solution, please let me know.
If this a good and reasonable feature, please add your advice. I could try contribute some codes on this feature.

[spencergibb]

Why don't you think spring-cloud-config-monitor with git webhooks is a good enough solution?

[jacobke]

Thank you for your fast response.

The real problem is that my other applications are not spring projects. They just send HTTP request to spring-config-server to load properties. They are designed to uncouple from configuration service, which means they pull properties at short interval. There is also no "/refresh" API to force refresh runtime properties.

By the way, spring-cloud-config-monitor is only in the latest release, and not available in central maven repositories. Even spring-cloud-config-monitor is deployed to public, lots of codes things should be done if we decide to convert all applications to spring projects.

So i want to do some cache things in config server, make less "git pull" request to git server.
This is the main propose.

[spencergibb]

How different is this than #157?

[spencergibb]

I think the difference is where the cache is happening, server (this issue) vs. client. Config server is stateless, that's part of it's simplicity. You could certainly add caching to your implementation of config server.

[jacobke]

@spencergibb thank your for your advice.
I will try to add cache feature in my forked codes.

[jacobke]

hi, guys, i commit a PR on #366 for this config-server cache feature.

But the implement is a bit wired. The detail is that i have to create a @Autowired cacheService to make "@Cacheable" works, because the EnvironmentRepository.findOne() is not called by Spring AOP proxy in EnvironmentController. The origin codes are:

    public Environment labelled(@PathVariable String name, @PathVariable String profiles,
            @PathVariable String label) {
        if (label != null && label.contains("(_)")) {
            // "(_)" is uncommon in a git branch name, but "/" cannot be matched
            // by Spring MVC
            label = label.replace("(_)", "/");
        }
        Environment environment = this.repository.findOne(name, profiles, label);
        return environment;
    }

Also to pass EnvironmentControllerTests, i have to check null for cacheService. Then codes becomes as following:

    @Autowired
    ConfigServerCacheService configServerCacheService;
    ......
    @RequestMapping("/{name}/{profiles}/{label:.*}")
    public Environment labelled(@PathVariable String name, @PathVariable String profiles,
            @PathVariable String label) {
        if (label != null && label.contains("(_)")) {
            // "(_)" is uncommon in a git branch name, but "/" cannot be matched
            // by Spring MVC
            label = label.replace("(_)", "/");
        }

        if (configServerCacheService == null) { // to pass-by EnvironmentControllerTests
            Environment environment = this.repository.findOne(name, profiles, label);
            return environment;
        } else {
            Environment cachedEnvironment = configServerCacheService.getEnvironment(name, profiles, label);
            if (cachedEnvironment == null) {
                Environment environment = this.repository.findOne(name, profiles, label);

                configServerCacheService.putEnvironmentCache(environment, name, profiles, label);
                return environment;
            }
            return cachedEnvironment;
        }
    }

I know there is all the bad code smell as i'm new to spring project. It seems EnvironmentRepository is designed to be out of spring AOP method, and i didn't found other places to inject @Cacheable annotation.

Then if you feel this cache feature is OK (regardless my bad implementation), let me go on how config server application (which use @EnableConfigServer) to triggle cache feature. application could add @EnableCaching and add a CacheManager bean. Then everything is done. My applications (mentioned above) are using this cache feature. And i can tuning cache performance in my application, where Spring Cache makes it very convenient.

The next is waiting for your advice on this feature. So far there are several code improvement like:

• add a built-in properties like "spring.cloud.config.server.usecache"=false, make cache feature only work under @conditional.
• add one constructor function in EnvironmentController for ConfigServerCacheService, make it could pass EnvironmentControllerTests with more clean code.
• or make EnvironmentRepository is initialize by Spring @Autowired, but this need more code refactor.

Anyway, thanks for reading this long PR. It's my first time contribute to open source project. The related contributor's agreement has been signed. If missed something, please let me know.