Bug #7162
Updated by Tom Clegg over 8 years ago
h3. Functional requirements requirements: * The Go SDK Keep client will talk to all accessible Keep services, regardless of their service type. * The client will send the X-Keep-Desired-Replication header in all PUT requests, and respect the X-Keep-Replicas-Stored header in the response, regardless of service type * The client only has one writer at a time writing to non-disk services, to avoid sending redundant requests (e.g., if it wants to 2 replicas of a block, it doesn't send the block to two gateways that will each replicate the block 2+ times). * Use "disk" timeouts for all services that don't have type "proxy". (Choosing timeouts based on type is rather wrong anyway -- but until we have a better approach, "api told us to use a proxy" is still the best readily available indication that the network between us and the keep service is slow.) h3. Implementation We don't get TBD: How should the "max replicas service X is able to store" information from the API server, but we'll move the code in that direction. * @KeepClient@ gets client choose a new attribute, @replicasPerService int@. * @DiscoverKeepServers@ sets @replicasPerService@ to @1@ if all non-ReadOnly services have @SvcType=="disk"@, otherwise @0@. (Note the current code forgets to reset @Using_proxy@ to @false@ if the API server stops giving out proxies between one call and the next. We should at least avoid making that mistake again -- and possibly fix that Using_proxy bug, since it's trivial.) * @DiscoverKeepServers@ adds all services to localRoots, not just disk and proxy. The only reason to look at SvcType is to choose which @this.setClientSettings*@ function to use. <pre><code class="diff"> - switch service.SvcType { - case "disk": - localRoots[service.Uuid] = url - case "proxy": - localRoots[service.Uuid] = url - this.Using_proxy = true - } + localRoots[service.Uuid] = url + if service.SvcType == "proxy" { + this.Using_proxy = true + } </code></pre> * @putReplicas@ reduces the number of concurrent writer threads according to @replicasPerService@. The easiest way to do this is probably something like: <pre><code class="diff"> - timeout for active < remaining_replicas { + replicasPerThread := this.replicasPerService + if replicasPerThread < 1 { + // unlimited or unknown + replicasPerThread = remaining_replicas + } + + for active * replicasPerThread < remaining_replicas { </code></pre> * @uploadToKeepServer@ should ignore this.Using_proxy here: <pre><code class="diff"> - if this.Using_proxy { req.Header.Add(X_Keep_Desired_Replicas, fmt.Sprint(this.Want_replicas)) - } </code></pre> non-disk, non-proxy services?