sijie commented on a change in pull request #1138: BP-31 BookKeeper Durability Anchor URL: https://github.com/apache/bookkeeper/pull/1138#discussion_r168363075
########## File path: site/bps/BP-31-durability ########## @@ -0,0 +1,134 @@ + +--- +title: "BP-31: BookKeeper Durability(Anchor)" +issue: https://github.com/apache/bookkeeper/BP-31-durability +state: 'Anchor BP' +release: "x.y.z" +--- +## Motivation +Apache BookKeeper is transitioning into a full fledged distributed storage that can keep the data for long term. Durability is paramount to achieve the status of trusted store. This Anchor BP discusses many gaps and areas of improvement. Each issue listed here will have another issue and this BP is expected to be updated when that issue is created. + +## Durability Contract +1. **Maintain WQ copies all the time**. If any ledger falls into under replicated state, there needs to be an SLA on how quickly the replication levels can be brought back to normal levels. +2. **Enforce Placement Policy** strictly during write and replication. +3. **Protect the data** against corruption on the wire or at rest. + +## Work Grouping (In the order of priority) +### Detect Durability Validation +First step is to understand the areas of durability breaches. Design metrics that record durability contract violations. +* At the Creation: Validate durability contract the extent is being created +* At the Deletion: Validate durability contract when extent is deleted +* During lifetime: Validate durability contract during the lifetime of the extent.(periodic validator) +* During Read: IO or Checksum errors in the read path +### Delete Discipline +* Build a single delete choke point with stringent validations +* Archival bit in the metadata to assist Two phase Deletes +* Stateful/Explicit Deletes +### Metadata Recovery +* Metadata recovery tool to reconstruct the metadata if the metadata server gets wiped out. This tool need to make sure that the data is readable even if we can't get all the metadata (ex: ctime) back. + +### Plug Durability Violations +Our first step is to identify durability viloations. That gives us the magnitude of the problem and areas that we need to focus. In this phase, fix high impact areas. +* Identify source of problems detected by the work we did in step-1 above (Detect Durability Validation) +* Rereplicate under replicated extents detected during write Review comment: would be good to change "extents" to "ledgers" :-) ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
