Safe Service Calls (safe-service)

Library for improving your server's fault tolerance

Overview

Modern Server applications can have a lot of dependencies on 3rd party client libraries, REST/Web Serices, etc. Very often these dependencies act as a "black boxes" for your system. It can lead to disasters for servers with common "thread per user request" architecture - if some services become not responsive, then with a high load there is a possibility that all server's threads will be in a waiting sets of this services and whole system become unresponsive. Following fault tolerance items implemented to avoid such situations:

"per-dependency" thread pulls to de-couple the service from the whole syste
Network time outs for not responsive services
Error handling and fallback procedures for rejected/failed requests
Use of cached values from previous successful calls

Essential Information

License

See LICENSE file

Binaries

All binaries will be published to Maven Central.

<dependency>
    <groupId>com.mudalov</groupId>
    <artifactId>safe-service</artifactId>
    <version>1.0-SNAPSHOT</version>
</dependency>

Usage of the library

Configuration

To change configation you need to have safe-service.conf file in your classpath. Configuration is stored in a HOCON format. Here is the list of supported properties and their default values:

# Number of thread allocated for Dependency group

threadsPerGroup : 5

# Max size of the working queue per Dependency group, -1 means "unlimited"

maxWorkQueueSize : -1

# Time Out (ms) to wait before rejecting the request

timeOut : 1000

# Custom Cache Factory implementation (instead of standard, based on EhCache)

cacheFactory : "com.mudalov.safe.cache.ehcache.EhCacheFactory"

# Each property can be overwritten for specified Dependency group,
# e.g. to increase threads pull size for high priority service

userInfoService {
    threadsPerGroup : 12
}

# or to increase time out for slow service

slowService {
    timeOut : 1500
}

API Example

Here is a simple example of executing action as a part of "userInfoService" dependency group, cached user information used in case of failure:

    User user = SafeCommands.create(new AbstractCachedCommand<User>() {
        @Override
        public String getKey() {
            // key to be used for cache, each dependency group stored in a separate cache region
            return userId.toString();
        }
        @Override
        public void onError(Exception cause) {
            log.error("Failed to get user, using cached value", e);
        }
        @Override
        public User action() throws Exception {
            return userService.getUser(userId);
        }
    }, "userInfoService").execute();

Please reference to unit tests for more detailed examples.

udalmik / safe-service