Proposal to use Souin as cache system core to cache-handler about cache-handler

[francislavoie]

I find that having Olric embedded in Caddy, while a good idea in theory, didn't seem that good in practice because configuration of Olric is not naturally compatible with Caddy and the way it works with the graceful reloads and app module system. Pointing to a yaml config feels foreign and awkward, especially for a module under the caddyserver org.

If Olric could work that way and be fully configured via structs with JSON tags and not have trouble reloading config (but persisting cache storage via UsagePool) then I'd be more comfortable with that.

Souin acting as a client for Olric is a pretty good compromise - we just need to clearly document how to run Olric alongside Caddy to provide the cache clustering.

[mholt]

Yeah, I mean, as long as it's an embedded, distributed cache -- as automatic as practical -- that is the goal of this module. 👍

[darkweak]

I don't think this will introduce more complexity because I just have to declare a new provider and implement my provider interface that's it imo.

[francislavoie]

I'd like to hear from @dunglas and @mholt on this, but 👍 to me. I was mainly concerned about the config UX but that's in a good place now I think. I don't know the specifics of the caching RFCs etc so I'd like people who know more to speak on that.

[mholt]

I saw how the configuration improved recently, so I am glad about that. I think this is fine, as long as it still has distributed caching. Would also need @dunglas' approval I think.

[buraksezer]

I have just realized that Souin doesn't use Olric in embedded-server mode. So Souin is just a client for an Olric cluster. In this scenario, there is no difference between memcache or Olric.

In the current version of cache-handler, Caddy servers form an Olric cluster to cache and serve content. So it functions as an in-process cache. With the current implementation of Souin, cache-handler is going to lost this functionality.

[mholt]

Ah, gotcha. One of the requirements of this cache handler is that it supports distributed caching.

[mholt]

I did like how easily autocache (groupcache wrapper) integrated as a Go library with JSON configuration, in the initial versions of this module. Wonder if that should be reconsidered. IMO the distributed caching should be embedded if possible.

[buraksezer]

If Olric could work that way and be fully configured via structs with JSON tags and not have trouble reloading config (but persisting cache storage via UsagePool) then I'd be more comfortable with that.

I think that JSON based configuration is easy to implement along with YAML. But reloading config without restarting the process is hard to implement and it requires extensive testing.

[darkweak]

I don't think it's a good idea to embed a distributed storage system because the replication will grow more and more along the time and will make the software growing indefinitely. IMO I could adapt the Olric provider in Souin to embed this but it will implicate the dump about the Olric instance each time the configuration reload. Then if we chose to never drop the existing db it will cause inconsistent. This approach prevent the data being dropped when the configuration changes and allow any cache or other software to access the data inside Olric.

TLDR I can embed but I'm not very fan about that.

[mholt]

the replication will grow more and more along the time and will make the software growing indefinitely.

Hm? The code doesn't grow indefinitely. The first version of this cache was mostly working, and wasn't a large amount of code.

[darkweak]

@mholt Okay, if you're sure about that, I'll make changes to be able to use Olric this way.

[darkweak]

It should be available on friday. What do you think about a new configuration key like embed_distributed ? It would be interresting to be able to chose between the existing Olric client mode and the embedded mode isn't it ?

[mholt]

I suppose that could be useful if people are already running a separate Olric instance. But it would probably add more complexity too.

[darkweak]

@buraksezer Do you agree with that ? darkweak/souin#80

[darkweak]

@mholt @francislavoie Olric embedded is now supported in Souin and can be configured through the caddy configuration file.

[francislavoie]

Can you show us an example of how Caddy would be configured with olric clustering? I don't see an example in the PR you merged.

[darkweak]

{
  "apps": {
    "souin_cache": {
      "headers": [
        "Content-Type",
        "Authorization"
      ],
      "log_level": "info",
      "olric": {
        "configuration": {
          "olricd": {
            "bindAddr": "0.0.0.0",
            "bindPort": 3320,
            "serializer": "msgpack",
            "keepAlivePeriod": "20s",
            "bootstrapTimeout": "5s",
            "partitionCount":  271,
            "replicaCount": 2,
            "writeQuorum": 1,
            "readQuorum": 1,
            "readRepair": false,
            "replicationMode": 1,
            "tableSize": 1048576,
            "memberCountQuorum": 1
          },
          "client": {
            "dialTimeout": "-1s",
            "readTimeout": "30s",
            "writeTimeout": "30s",
            "keepAlive": "150s",
            "minConn": 1,
            "maxConn": 100
          },
          "logging": {
            "verbosity": 6,
            "level": "DEBUG",
            "output": "stderr"
          },
          "memberlist": {
            "environment": "local",
            "bindAddr": "0.0.0.0",
            "bindPort": 3322,
            "enableCompression": false,
            "joinRetryInterval": "10s",
            "maxJoinAttempts": 2
          }
        }
      },
      "ttl": "1000s"
    },
    "http": {
      "servers": {
        "": {
          "listen": [":80"],
          "routes": [
            {
              "match": [
                {
                  "header": {
                    "Content-Type": ["*"]
                  },
                  "path": [
                    "/a*"
                  ]
                }
              ],
              "handle": [
                {
                  "handler": "souin_cache",
                  "ttl": "30s"
                }
              ]
            },
            {
              "match": [
                {
                  "header": {
                    "Content-Type": ["*"]
                  },
                  "path": [
                    "/b*"
                  ]
                }
              ],
              "handle": [
                {
                  "handler": "souin_cache",
                  "headers": []
                }
              ]
            },
            {
              "match": [
                {
                  "header": {
                    "Content-Type": ["*"]
                  },
                  "path": [
                    "*"
                  ]
                }
              ],
              "handle": [
                {
                  "handler": "souin_cache"
                }
              ]
            }
          ]
        }
      }
    }
  }
}