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Jian Zhang updated HDFS-17302: ------------------------------ Summary: RBF: ProportionRouterRpcFairnessPolicyController-Sharing and Isolating. (was: RBF: ProportionRouterRpcFairnessPolicyController-support proportional allocation of semaphores) > RBF: ProportionRouterRpcFairnessPolicyController-Sharing and Isolating. > ----------------------------------------------------------------------- > > Key: HDFS-17302 > URL: https://issues.apache.org/jira/browse/HDFS-17302 > Project: Hadoop HDFS > Issue Type: New Feature > Components: rbf > Reporter: Jian Zhang > Assignee: Jian Zhang > Priority: Major > Labels: pull-request-available > Attachments: HDFS-17302.001.patch, HDFS-17302.002.patch > > > h2. Current shortcomings > [HDFS-14090|https://issues.apache.org/jira/browse/HDFS-14090] provides a > StaticRouterRpcFairnessPolicyController to support configuring different > handlers for different ns. Using the StaticRouterRpcFairnessPolicyController > allows the router to isolate different ns, and the ns with a higher load will > not affect the router's access to the ns with a normal load. But the > StaticRouterRpcFairnessPolicyController still falls short in many ways, such > as: > 1. *Configuration is inconvenient and error-prone*: When I use > StaticRouterRpcFairnessPolicyController, I first need to know how many > handlers the router has in total, then I have to know how many nameservices > the router currently has, and then carefully calculate how many handlers to > allocate to each ns so that the sum of handlers for all ns will not exceed > the total handlers of the router, and I also need to consider how many > handlers to allocate to each ns to achieve better performance. Therefore, I > need to be very careful when configuring. Even if I configure only one more > handler for a certain ns, the total number is more than the number of > handlers owned by the router, which will also cause the router to fail to > start. At this time, I had to investigate the reason why the router failed to > start. After finding the reason, I had to reconsider the number of handlers > for each ns. > 2. *Extension ns is not supported*: During the running of the router, if a > new ns is added to the cluster and a mount is added for the ns, but because > no handler is allocated for the ns, the ns cannot be accessed through the > router. We must reconfigure the number of handlers and then refresh the > configuration. At this time, the router can access the ns normally. When we > reconfigure the number of handlers, we have to face disadvantage 1: > Configuration is inconvenient and error-prone. > 3. *Waste handlers*: The main purpose of proposing > RouterRpcFairnessPolicyController is to enable the router to access ns with > normal load and not be affected by ns with higher load. First of all, not all > ns have high loads; secondly, ns with high loads do not have high loads 24 > hours a day. It may be that only certain time periods, such as 0 to 8 > o'clock, have high loads, and other time periods have normal loads. Assume > there are 2 ns, and each ns is allocated half of the number of handlers. > Assume that ns1 has many requests from 0 to 14 o'clock, and almost no > requests from 14 to 24 o'clock, ns2 has many requests from 12 to 24 o'clock, > and almost no requests from 0 to 14 o'clock; when it is between 0 o'clock and > 12 o'clock and between 14 o'clock and 24 o'clock, only one ns has more > requests and the other ns has almost no requests, so we have wasted half of > the number of handlers. > 4. *Only isolation, no sharing*: The staticRouterRpcFairnessPolicyController > does not support sharing, only isolation. I think isolation is just a means > to improve the performance of router access to normal ns, not the purpose. It > is impossible for all ns in the cluster to have high loads. On the contrary, > in most scenarios, only a few ns in the cluster have high loads, and the > loads of most other ns are normal. For ns with higher load and ns with normal > load, we need to isolate their handlers so that the ns with higher load will > not affect the performance of ns with lower load. However, for nameservices > that are also under normal load, or are under higher load, we do not need to > isolate them, these ns of the same nature can share the handlers of the > router; The performance is better than assigning a fixed number of handlers > to each ns, because each ns can use all the handlers of the router. > h2. New features > Based on the above staticRouterRpcFairnessPolicyController, there are > deficiencies in usage and performance. I provide a new > RouterRpcFairnessPolicyController: > ProportionRouterRpcFairnessPolicyController (maybe with a better name) to > solve the above major shortcomings. > 1. *More user-friendly configuration* : Supports allocating handlers > proportionally to each ns. For example, we can give ns1 a handler ratio of > 0.2, then ns1 will use 0.2 of the total number of handlers on the router. > Using this method, we do not need to confirm in advance how many handlers the > router has. > 2. *Sharing* : -- This message was sent by Atlassian Jira (v8.20.10#820010) --------------------------------------------------------------------- To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org