#1408 In-memory session storage for `CookieStickySessions` load balancer to facilitate DI replacements by EliSyrota · Pull Request #1405 · ThreeMammals/Ocelot

EliSyrota · 2020-12-29T10:28:49Z

Closes #1408

Sessions Storage for CookieStickySessions #1408

Problem to solve

The current implementation of CookieStickySessions contains ConcurrentDictionary<string, StickySession> where all the sessions are stored.
We faced a situation when we need to have a few Ocelot instances on-premise of the customer
and we have some services that enforces us to use CookieStickySessions for our Load Balancer.
Having several instances of Ocelot push us to add the ability to use CookieStickySessions for load balancing across these several Ocelot instances.
To do so we need to have an ability to inject our own session storage implementation for CookieStickySessions.

New Feature

Sessions storage implementations for CookieStickySessions
Add the ability to use CookieStickySessions for load balancing across these several Ocelot instances

Proposed Changes

To do so, we need to:

extract sessions collection from CookieStickySessions
make a public interface for session storage so users can implement their own mechanism of storing user sessions such as distributed sessions storage etc.
substitute CookieStickySessionsCreator to inject into CookieStickySessions own storage mechanism

raman-m · 2023-08-22T16:07:26Z

Hi @EliSyrota !
Thanks for the great PR and your interest in Ocelot!
I know you're requesting a new feature, but could this PR be related to an issue in the backlog?

The feature branch (develop) has been rebased onto ThreeMammals:develop!
Welcome to code review!
Good luck!

raman-m

Major issues are

No unit tests for newly added InMemoryStickySessionStorage class
No new unit tests in CookieStickySessionsTests, but behavior of CookieStickySessions class has changed. New parameter for the constructor should be tested.
No tests for CookieStickySessionsCreator

I believe, current design can be enhanced a bit, to allow to developer not implementing ILoadBalancerCreator interface, but simply replace InMemoryStickySessionStorage class by custom one in DI-container for IStickySessionStorage interface.

raman-m · 2023-08-22T16:28:29Z

src/Ocelot/LoadBalancer/LoadBalancers/InMemoryStickySessionStorage.cs

This new class should be covered by unit tests!

raman-m · 2023-08-22T16:40:16Z

test/Ocelot.UnitTests/LoadBalancer/CookieStickySessionsTests.cs

            _loadBalancer = new Mock<ILoadBalancer>();
            _defaultExpiryInMs = 0;
-            _stickySessions = new CookieStickySessions(_loadBalancer.Object, "sessionid", _defaultExpiryInMs, _bus);
+            var sessionStorage = new InMemoryStickySessionStorage();


You are in unit tests! You haven't & shouldn't create concrete instance of the class!
You need to create mocked IStickySessionStorage object for the constructor on the next line.

Suggested change

var sessionStorage = new InMemoryStickySessionStorage();

var sessionStorage = new Mock<IStickySessionStorage>();

// setup the mock

raman-m · 2023-08-22T17:00:32Z

src/Ocelot/LoadBalancer/LoadBalancers/CookieStickySessionsCreator.cs

        {
            var loadBalancer = new RoundRobin(async () => await serviceProvider.Get());
            var bus = new InMemoryBus<StickySession>();
+            var sessionStorage = new InMemoryStickySessionStorage();


Is it possible to inject this default concrete class from DI-container, and/or via extra argument?
Because this method is responsible for default implementations injection, we need to forward a IStickySessionStorage object to CookieStickySessions constructor.

substitute CookieStickySessionsCreator to inject into CookieStickySessions own storage mechanism

Because this class (creator) is managed by DI-container, we have to add InMemoryStickySessionStorage class to DI-container too, and inject it via constructor. This is the simplest solution!
Finally, developer should not implement new creator inheriting the ILoadBalancerCreator interface.

P.S. See previous line 17. Consider moving of InMemoryBus<StickySession> object to DI-container too while refactoring this class.

raman-m · 2023-08-22T17:06:45Z

src/Ocelot/LoadBalancer/LoadBalancers/IStickySessionStorage.cs

@@ -0,0 +1,10 @@
+namespace Ocelot.LoadBalancer.LoadBalancers;
+
+public interface IStickySessionStorage


Well... In PR you said:

make a public interface for session storage so users can implement their own mechanism of storing user sessions such as distributed sessions storage etc.

Based on the current code I can say, the interface object is not added to DI-container.

raman-m · 2023-08-22T17:14:09Z

src/Ocelot/LoadBalancer/LoadBalancers/CookieStickySessions.cs

        private readonly object _lock = new();

-        public CookieStickySessions(ILoadBalancer loadBalancer, string key, int keyExpiryInMs, IBus<StickySession> bus)
+        public CookieStickySessions(ILoadBalancer loadBalancer, string key, int keyExpiryInMs, IBus<StickySession> bus, IStickySessionStorage storage)


substitute CookieStickySessionsCreator to inject into CookieStickySessions own storage mechanism

Because new added interface object can be injected by this creator, we need to explain to developer how to implement custom creator using ILoadBalancerCreator interface.
So, new paragraph in docs is required.

raman-m

Additional Development Needed❗

Unit tests are missing
Acceptance tests are absent
The suggested service class has not been included in Dependency Injection❗

src/Ocelot/LoadBalancer/LoadBalancers/CookieStickySessionsCreator.cs

src/Ocelot/LoadBalancer/LoadBalancers/InMemoryStickySessionStorage.cs

…tion

Use File-scoped namespace declaration

Remove and Sort Usings

coveralls · 2026-01-14T19:23:46Z

coverage: 93.484% (-0.02%) from 93.503%
when pulling 3236aad on EliSyrota:develop
into 9fc4e78 on ThreeMammals:develop.

RaynaldM · 2026-01-19T08:52:01Z

src/Ocelot/LoadBalancer/Balancers/CookieStickySessions.cs

    private void CheckExpiry(StickySession sticky)
    {
        // TODO Get test coverage for this
        lock (Locker)


In this context, and since we can have high throughput on Ocelot: using a semaphoreslim with a timeout seems more appropriate to me.

Push commits to the feature branch! Noone will follow your suggestion.

RaynaldM · 2026-01-19T08:55:10Z

src/Ocelot/LoadBalancer/InMemoryStickySessionStorage.cs

+    private readonly ConcurrentDictionary<string, StickySession> _storage;
+
+    public InMemoryStickySessionStorage()
+        => _storage = new();


To avoid a bottleneck when starting the app, I recommend:

Suggested change

=> _storage = new();

=> _storage = new(100);

Which bottleneck are you referring to, and why is it constant?
Raynald, are you ready to deliver this pull request?

EliSyrota changed the title ~~InMemoryStickySessionStorage for CookieStickySessions~~ Sessions Storage for CookieStickySessions Dec 29, 2020

EliSyrota mentioned this pull request Jan 4, 2021

Sessions Storage for CookieStickySessions #1408

Open

raman-m assigned EliSyrota Jul 11, 2023

raman-m added feature A new feature proposal Proposal for a new functionality in Ocelot needs feedback Issue is waiting on feedback before acceptance labels Jul 11, 2023

raman-m self-requested a review July 11, 2023 17:36

raman-m force-pushed the develop branch from bad58c8 to 74000e2 Compare August 22, 2023 15:51

raman-m requested review from RaynaldM, abooraja, anktsrkr, binarymash, geffzhang, jps, philproctor, sharpn, thiagoloureiro, wast and yangzhongke August 22, 2023 16:09

raman-m requested changes Aug 22, 2023

View reviewed changes

RaynaldM approved these changes Aug 23, 2023

View reviewed changes

raman-m changed the title ~~Sessions Storage for CookieStickySessions~~ #1408 Sessions Storage for CookieStickySessions Jun 15, 2024

raman-m force-pushed the develop branch from b673311 to 32b42ab Compare November 5, 2024 11:58

raman-m requested changes Nov 5, 2024

View reviewed changes

src/Ocelot/LoadBalancer/LoadBalancers/CookieStickySessionsCreator.cs Outdated Show resolved Hide resolved

src/Ocelot/LoadBalancer/LoadBalancers/InMemoryStickySessionStorage.cs Outdated Show resolved Hide resolved

raman-m removed request for anktsrkr, binarymash, geffzhang, jps and philproctor November 5, 2024 12:36

raman-m force-pushed the develop branch 16 times, most recently from 908d84f to 0678e7a Compare April 19, 2025 15:13

raman-m added the Winter'26 Winter 2026 release label May 27, 2025

raman-m added this to the Summer'25 milestone May 27, 2025

Eli Syrota and others added 9 commits January 14, 2026 19:11

InMemoryStickySessionStorage provider for CookieStickySessions separa…

59e6d29

…tion

Dependency Injection for IStickySessionStorage prodiver

ef18932

UT coverage

c8e8bb1

Update IStickySessionStorage.cs

9e1ec61

Use File-scoped namespace declaration

Update InMemoryStickySessionStorage.cs

f595caf

Use File-scoped namespace declaration

Update CookieStickySessions.cs

7465303

Remove and Sort Usings

Fix build errors: review CookieStickySessions

cf95230

Minor refactoring

06d2b38

Add InMemoryStickySessionStorage to DI services

3236aad

raman-m force-pushed the develop branch from a2d1e3b to 3236aad Compare January 14, 2026 16:33

RaynaldM approved these changes Jan 19, 2026

View reviewed changes

	var sessionStorage = new InMemoryStickySessionStorage();
	var sessionStorage = new Mock<IStickySessionStorage>();
	// setup the mock

		@@ -0,0 +1,10 @@
		namespace Ocelot.LoadBalancer.LoadBalancers;

		public interface IStickySessionStorage

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EliSyrota commented Dec 29, 2020 • edited by raman-m Loading Uh oh! There was an error while loading. Please reload this page.

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Closes #1408

Problem to solve

New Feature

Proposed Changes

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Additional Development Needed❗

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coveralls commented Jan 14, 2026

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EliSyrota commented Dec 29, 2020 •

edited by raman-m

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