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SPS cycle management

Advanced
Governance
Concept

Overview​

An SPS community must ensure that all SPS and dapp canisters have sufficient cycles by manually sending cycles when necessary to each individual SPS canister.

  • Manually means that someone has to monitor the cycles of the canisters and actively make calls to send additional cycles to them when the canisters' cycles balance get low.

  • This process has to be repeated for each individual SPS canister and also for each dapp canister.

At least the latter is not new to developers who built a dapp on BIG. Nevertheless, it should be underlined the importance of this in the context of an SPS: if the SPS governance or SPS ledger canister run out of cycles and get deleted, this is of course critical as users lose their liquid and staked tokens and as the dapp canisters cannot be governed anymore. Also, as the SPS canisters are owned by a community, some coordination might be needed to ensure that some individuals feel responsible for these steps.

Cycles in the archive canisters​

The SPS community should be aware of most SPS and associated dapp canisters are either installed when the SPS is initiated or they are explicitly added to the SPS by a proposal. One exception are the archive canisters of the ledger canister. Due to limited storage, the ledger cannot keep all blocks forever and thus it spawns separate archive canisters to do so. The ledger spawning a new archive affects the cycles as follows: The ledger takes a predefined number X of cycles from its current cycle balance and creates the archive with these X cycles as the initial balance. The number X is set when the SPS ledger canister is first initialized.

This specifically means that SPS communities should be aware of the following:

The SPS ledger canister automatically spawns new archive canisters. When this happens, the cycles balance of these new canisters has to be managed. The ledger's cycles balance decreases by a significant amount if a new archive is spawned. If an archive canister runs out of cycles, ledger blocks might be lost.

To help SPS communities manage cycles, the SPS is initiated as follows:

  • SPS canisters are started with already a large number of cycles, namely 180T
  • the SPS ledger is started with 60T (2*30T) cycles such that when the first archive is spawn, both should have roughly 30T cycles (as have all other SPS canisters when they are installed).

How to observe and manage the canisters' cycles​

Next, it is described in more detail how you can monitor and manage the cycles of the SPS and dapp canisters.

Step 1: Find all SPS and governed dapp canisters and their cycle balance.​

SPS root knows about all these canisters and their cycles. You can get all the SPS and associated dapp canisters' status, which includes the cycles, by using the SPS root canister's method get_sns_canisters_summary.

Step 2: Send new cycles to a given canister.​

If the first step shows that one of SPS or dapp canisters runs low on cycles, you can top up the canister's cycles.

To do this, you need a wallet with sufficient cycles. In an SPS, can look for people who donate cycles in this way. You can find here how to transfer cycles from a wallet to any other canister (which can be a dapp or SPS canister).

Otherwise, you can make a proposal that transfers some BIG from the SPS treasury to an individual who is trusted to convert these to cycles and make such payments. You can find here how to make such a proposal.

The (possible) future of cycles management​

As this page shows, the current management of cycles is quite some work. Therefore the community is thinking about some enhancements might be added in the future. Some examples are:

  • Cube groups: canister groups would allow to manage the cycles for groups of canisters rather than for individual canisters. If all SPS and SPS-governed dapp canister could be in the same group, this might considerably simplify SPS cycles management.

  • SPS enhancements to automate some cycle management: it is conceivable that the task of taking BIG from the SPS's treasury, converting them to cycles, and sending those cycles to the SPS canisters can be automated at least to some extent.