1. Where is my cache?
Architectural patterns for caching
microservices
Rafał Leszko
@RafalLeszko
rafalleszko.com
Hazelcast

2. About me
● Integration Team Lead at Hazelcast
● Worked at Google and CERN
● Author of the book "Continuous Delivery
with Docker and Jenkins"
● Trainer and conference speaker
● Live in Kraków, Poland

3. About Hazelcast
● Distributed Company
● Open Source Software
● 140+ Employees
● Products:
○ Hazelcast IMDG
○ Hazelcast Jet
○ Hazelcast Cloud
@Hazelcast
www.hazelcast.com

4. ● Introduction
● Caching Architectural Patterns
○ Embedded
○ Embedded Distributed
○ Client-Server
○ Cloud
○ Sidecar
○ Reverse Proxy
○ Reverse Proxy Sidecar
● Summary
Agenda

5. Service 1
Service 2
v1
Service 2
v2
Service 1
Service 4
v1
Service 4
v2
Service 4
v3
Ruby
Microservice World

6. Microservice World
Service 1
Service 2
v1
Service 2
v2
Service 1
Service 4
v1
Service 4
v2
Service 4
v3
Ruby
cache
cache
cache
cache

7. Microservice World
Service 1
Service 2
v1
Service 2
v2
Service 1
Service 4
v1
Service 4
v2
Service 4
v3
Ruby
cache
cache
cache

8. Microservice World
Service 1
Service 2
v1
Service 2
v2
Service 1
Service 4
v1
Service 4
v2
Service 4
v3
Ruby
cache
cache
cache

9. ● Introduction ✔
● Caching Architectural Patterns
○ Embedded
○ Embedded Distributed
○ Client-Server
○ Cloud
○ Sidecar
○ Reverse Proxy
○ Reverse Proxy Sidecar
● Summary
Agenda

10. 1. Embedded

11. Application
Load Balancer
Cache
Application
Cache
Request
Embedded Cache

12. private ConcurrentHashMap<String, String> cache =
new ConcurrentHashMap<>();
private String processRequest(String request) {
if (cache.contains(request)) {
return cache.get(request);
}
String response = process(request);
cache.put(request, response);
return response;
}
Embedded Cache (Pure Java implementation)

13. private ConcurrentHashMap<String, String> cache =
new ConcurrentHashMap<>();
private String processRequest(String request) {
if (cache.contains(request)) {
return cache.get(request);
}
String response = process(request);
cache.put(request, response);
return response;
}
Embedded Cache (Pure Java implementation)

14. ● No Eviction Policies
● No Max Size Limit
(OutOfMemoryError)
● No Statistics
● No built-in Cache Loaders
● No Expiration Time
● No Notification Mechanism
Java Collection is not a Cache!

15. CacheBuilder.newBuilder()
.initialCapacity(300)
.expireAfterAccess(Duration.ofMinutes(10))
.maximumSize(1000)
.build();
Embedded Cache (Java libraries)

16. Embedded Cache (Java libraries)
CacheBuilder.newBuilder()
.initialCapacity(300)
.expireAfterAccess(Duration.ofMinutes(10))
.maximumSize(1000)
.build();

17. Caching Application Layer
@Service
public class BookService {
@Cacheable("books")
public String getBookNameByIsbn(String isbn) {
return findBookInSlowSource(isbn);
}
}

18. Caching Application Layer
@Service
public class BookService {
@Cacheable("books")
public String getBookNameByIsbn(String isbn) {
return findBookInSlowSource(isbn);
}
}
Be Careful, Spring uses ConcurrentHashMap by default!

19. Application
Load Balancer
Cache
Application
Cache
Request
Embedded Cache

20. 1*. Embedded Distributed

21. Application
Application
Load Balancer
Cache
Cache
Request
Hazelcast
Cluster
Embedded Distributed Cache

22. @Configuration
public class HazelcastConfiguration {
@Bean
CacheManager cacheManager() {
return new HazelcastCacheManager(
Hazelcast.newHazelcastInstance());
}
}
Embedded Distributed Cache (Spring with Hazelcast)

23. Hazelcast Discovery Plugins

24. Hazelcast Discovery Plugins

25. Hazelcast Discovery Plugins

26. Application
Application
Load Balancer
Cache
Cache
Request
Hazelcast
Cluster
Embedded Distributed Cache

27. Embedded Cache
Pros Cons
● Simple configuration /
deployment
● Low-latency data access
● No separate Ops Team
needed
● Not flexible management
(scaling, backup)
● Limited to JVM-based
applications
● Data collocated with
applications

28. ● Introduction ✔
● Caching Architectural Patterns
○ Embedded ✔
○ Embedded Distributed ✔
○ Client-Server
○ Cloud
○ Sidecar
○ Reverse Proxy
○ Reverse Proxy Sidecar
● Summary
Agenda

29. 2. Client-Server

30. Application
Load Balancer
Application
Request
Cache Server
Client-Server Cache

31. Application
Load Balancer
Application
Request
Cache Server
Client-Server Cache

32. Application
Load Balancer
Application
Request
Cache Server
Client-Server Cache
Separate Management:
● backups
● (auto) scaling
● security
Ops Team

33. Application
Load Balancer
Application
Request
Cache Server
Client-Server Cache

34. Application
Load Balancer
Application
Request
Cache Server
Client-Server Cache

35. Client-Server Cache

36. Client-Server Cache

37. Client-Server Cache
$ hz start
Starting Hazelcast Cache Server (standalone)

38. Client-Server Cache
Starting Hazelcast Cache Server (Kubernetes)
$ helm install hazelcast/hazelcast

39. Client-Server Cache
Hazelcast Client (Kubernetes):
@Configuration
public class HazelcastClientConfiguration {
@Bean
CacheManager cacheManager() {
return new HazelcastCacheManager();
}
}
Starting Hazelcast Cache Server (Kubernetes)
$ helm install hazelcast/hazelcast

40. Application
Load Balancer
Application
Request
Cache Server
Client-Server Cache
Ops Team
Separate Management:
● backups
● (auto) scaling
● security

41. 2*. Cloud

42. Application
Load Balancer
Application
Request
Cloud (Cache as a Service)

43. Application
Load Balancer
Application
Request
Cloud (Cache as a Service)
Management:
● backups
● (auto) scaling
● security
Ops Team

44. Application
Load Balancer
Application
Request
Cloud (Cache as a Service)
Management:
● backups
● (auto) scaling
● security
Ops Team

45. Application
Load Balancer
Application
Request
Cloud (Cache as a Service)

46. @Configuration
public class HazelcastCloudConfiguration {
@Bean
CacheManager cacheManager() {
ClientConfig clientConfig = new ClientConfig();
clientConfig.getNetworkConfig().getCloudConfig()
.setEnabled(true)
.setDiscoveryToken("KSXFDTi5HXPJGR0wRAjLgKe45tvEEhd");
clientConfig.setClusterName("test-cluster");
return new HazelcastCacheManager(
HazelcastClient.newHazelcastClient(clientConfig));
}
}
Cloud (Cache as a Service)

47. Client-Server (Cloud) Cache
Pros
● Data separate from
applications
● Separate management
(scaling, backup)
● Programming-language
agnostic
Cons
● Separate Ops effort
● Higher latency
● Server network requires
adjustment (same region,
same VPC)

48. ● Introduction ✔
● Caching Architectural Patterns
○ Embedded ✔
○ Embedded Distributed ✔
○ Client-Server ✔
○ Cloud ✔
○ Sidecar
○ Reverse Proxy
○ Reverse Proxy Sidecar
● Summary
Agenda

49. 3. Sidecar

50. Kubernetes Service
(Load Balancer)
Request
Hazelcast
Cluster
Kubernetes POD
Application Container
Cache Container
Application Container
Cache Container
Kubernetes POD
Sidecar Cache

51. Sidecar Cache
Similar to Embedded:
● the same physical machine
● the same resource pool
● scales up and down together
● no discovery needed (always localhost)
Similar to Client-Server:
● different programming language
● uses cache client to connect
● clear isolation between app and cache

52. @Configuration
public class HazelcastSidecarConfiguration {
@Bean
CacheManager cacheManager() {
ClientConfig clientConfig = new ClientConfig();
clientConfig.getNetworkConfig()
.addAddress("localhost:5701");
return new HazelcastCacheManager(HazelcastClient
.newHazelcastClient(clientConfig));
}
}
Sidecar Cache

53. Sidecar Cache
apiVersion: apps/v1
kind: Deployment
...
spec:
template:
spec:
containers:
- name: application
image: leszko/application
- name: hazelcast
image: hazelcast/hazelcast

54. Sidecar Cache
Pros Cons
● Simple configuration
● Programming-language
agnostic
● Low latency
● Some isolation of data and
applications
● Limited to container-based
environments
● Not flexible management
(scaling, backup)
● Data collocated with
application PODs

55. ● Introduction ✔
● Caching Architectural Patterns
○ Embedded ✔
○ Embedded Distributed ✔
○ Client-Server ✔
○ Cloud ✔
○ Sidecar ✔
○ Reverse Proxy
○ Reverse Proxy Sidecar
● Summary
Agenda

56. 4. Reverse Proxy

57. Application
Load
Balancer
Cache
Application
Request
Reverse Proxy Cache

58. Reverse Proxy Cache
http {
...
proxy_cache_path /data/nginx/cache
keys_zone=one:10m;
...
}

59. ● Only for HTTP
● Not distributed
● No High Availability
● Data stored on the disk
NGINX Reverse Proxy Cache Issues

60. 4*. Reverse Proxy Sidecar

61. Kubernetes Service
(Load Balancer)
Request
Hazelcast
Cluster
Kubernetes POD
Application Container
Reverse Proxy Cache
Container
Application Container
Reverse Proxy Cache
Container
Kubernetes POD
Reverse Proxy Sidecar Cache

63. Good

64. Reverse Proxy Sidecar Cache
Service 1
Service 2
v1
Service 2
v2
Service 1
Service 4
v1
Service 4
v2
Service 4
v3
Ruby

65. Reverse Proxy Sidecar Cache
Service 1
Service 2
v1
Service 2
v2
Service 1
Service 4
v1
Service 4
v2
Service 4
v3
Ruby

67. Bad

69. Reverse Proxy Cache
@CacheEvict(value = "someValue", allEntries = true)
public void evictAllCacheValues() {}
Application Cache:

70. Reverse Proxy Cache
@CacheEvict(value = "someValue", allEntries = true)
public void evictAllCacheValues() {}
Application Cache:
Proxy Cache:
http {
...
location / {
add_header Cache-Control public;
expires 86400;
etag on;
}
}

71. Reverse Proxy (Sidecar) Cache
Pros Cons
● Configuration-based (no
need to change
applications)
● Programming-language
agnostic
● Consistent with containers
and microservice world
● Difficult cache invalidation
● No mature solutions yet
● Protocol-based (e.g. works
only with HTTP)

72. ● Introduction ✔
● Caching Architectural Patterns
○ Embedded ✔
○ Embedded Distributed ✔
○ Client-Server ✔
○ Cloud ✔
○ Sidecar ✔
○ Reverse Proxy ✔
○ Reverse Proxy Sidecar ✔
● Summary
Agenda

73. Summary

74. application-aware?

75. application-aware?
containers?
no

76. application-aware?
containers?
Reverse Proxy
no
no

77. application-aware?
containers?
Reverse Proxy
Reverse Proxy
Sidecar
no
yes no

78. application-aware?
containers?
Reverse Proxy
Reverse Proxy
Sidecar
lot of data?
security restrictions?
yes no
yes no

79. application-aware?
containers?
Reverse Proxy
Reverse Proxy
Sidecar
lot of data?
security restrictions?
language-agnostic?
containers?
yes no
yes nono

80. application-aware?
containers?
Reverse Proxy
Reverse Proxy
Sidecar
lot of data?
security restrictions?
language-agnostic?
containers?
Embedded
(Distributed)
yes no
yes no
no
no

81. application-aware?
containers?
Reverse Proxy
Reverse Proxy
Sidecar
lot of data?
security restrictions?
language-agnostic?
containers?
Embedded
(Distributed)
Sidecar
yes no
yes
yes no
no
no

82. application-aware?
containers?
Reverse Proxy
Reverse Proxy
Sidecar
lot of data?
security restrictions?
language-agnostic?
containers?
Embedded
(Distributed)
Sidecar
cloud?
yes no
yes
yes
yes no
no
no

83. application-aware?
containers?
Reverse Proxy
Reverse Proxy
Sidecar
lot of data?
security restrictions?
language-agnostic?
containers?
Embedded
(Distributed)
Sidecar
cloud?
Client-Server
yes no
yes
yes
yes no
nono
no

84. application-aware?
containers?
Reverse Proxy
Reverse Proxy
Sidecar
lot of data?
security restrictions?
language-agnostic?
containers?
Embedded
(Distributed)
Sidecar
cloud?
Client-ServerCloud
yes no
yes
yes yes
yes no
nono
no

85. Resources
● Code for this talk:
https://github.com/leszko/caching-patterns
● Hazelcast Sidecar Container Pattern:
https://hazelcast.com/blog/hazelcast-sidecar-container-pattern/
● Hazelcast Reverse Proxy Sidecar Caching Prototype:
https://github.com/leszko/caching-injector
● NGINX HTTP Reverse Proxy Caching:
https://www.nginx.com/resources/videos/best-practices-for-caching/

86. Thank You!
Rafał Leszko
@RafalLeszko
rafalleszko.com