ADR 0408 section 4 says no key of the chain is removed, a delete marker included. The Backend loses Remove and the Chain RemoveAssignment. An unassignment, and the end of a value only pulled in by another, write the value again with ended set, by compare-and-set; assigning it again writes a fresh standing value over it. A value with ended or a state is no assignment (Assignment.Stands) to the assignment lists, the joins, forgetting a module, seat holdings, the given values, the move and the assignment-changed event.
Once chain_moved records the kind, Assign, Unassign and Assigned write and read the keys <node>.<module>, and every join of the store that read assignments is made from the bucket: where a module runs, what is behind, what a machine awaits, a given value due for replacement, taking a module, and whether a module may be forgotten (refused while a standing assignment names it). An unassignment ends the key with a marker and keeps its earlier values, as it removed the row; no ended or pending mark is written yet. The generation rises with each change, and a seat held by an assignment goes with it: the foreign key from seat_holding is dropped by migration 0104 and the controller says both. The provisioner's plan is kept in the values by a pass of the tick that writes that one field by compare-and-set; the assignment-changed event is said from what the bucket holds, whoever wrote it. The start moves the rows with what each machine was last sent, keeping a plan the mirror put in a value.
Once chain_moved records the kind, a plan is a key of the rollouts bucket under its id and the open batch is the same key in state assembling. A save refuses a copy another save moved since (the plan's own Revision, kept in its value, counts saves) and keeps the merges the record holds, so a copy read before a merge moved cannot lay it back. The merges a batch or walk answers are the record's held field, with the columns the table had; a merge no plan answers stays, flagged, in the record that held it last, or in the record kept for those. A merge moved to a plan is written to the receiving record first and then taken from the giving one; one found in both is read from the one it entered last and repaired at the next cut. Plans and merges are read from a view kept by one watch of the bucket. A bus that does not answer, a lease lost and a key moved are now not-now like the store being away, so a merge whose plan could not be written is held and handed over again, never acknowledged. The start moves release_plan and batched_merge into the bucket, one kind, counted against both tables.
A request is the build's record under the id its outcome will carry, in state asked; the outcome takes its place and keeps the request beside it, so assign, the pending assignments and the planner read the builds bucket alone. The bucket removes no key, so a request past thirty days is not listed instead of deleted. The move folds build_request into the same records (one kind, builds, counted against both tables) and marks the requests never handed over to be asked again once: claimed before it is asked and settled after, so a crash loses the ask rather than making it twice. Also tests the chain buckets' options on a real bus, the assignments' mirror options included.
Once chain_moved records the kind, RecordBuild and every build read go through the chain (reuse key and published added); before that the tables are read as before. The serving controller copies the rows at its start, holding the lease: idempotent per key, rows counted against keys, the largest value measured, a refusal (urgent condition, nothing switched) on a count that differs or a value over the bus's largest, and a re-read when the table took a row meanwhile. ForTest attaches the chain in memory with builds moved; ForTestBefore leaves it unmoved. Build requests, gates and the other kinds are still in their tables.
internal/chain holds typed Build, Rollout and Assignment and a Backend with no delete or purge, in memory and on the bus. The builds and rollouts buckets are asserted with history 64, no age and values up to just under a mebibyte; the assignments bucket gets the same, keeping its marker age because a stream cannot be made to disallow message ages. Migration 0104 makes the one-row chain_moved switch. The controller keeps no consolidated schema, so 0104 is the whole schema change. Nothing reads the buckets yet.
jschoubben