forked from TrueCloudLab/frostfs-node
[#1149] writecache: Prevent corruption in Head
Also, remove optimization comments: 1. Having to maintain an execute the same logic for headers as for objects is quite inefficient, as it increases memory footprint. 2. Unmarshaling object is a cheap operation if data slice is in memory. 3. For unmarshaling header-only, I think we need SDK support. Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
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1 changed files with 6 additions and 9 deletions
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@ -16,9 +16,13 @@ func (c *cache) Get(addr *addressSDK.Address) (*objectSDK.Object, error) {
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c.mtx.RLock()
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for i := range c.mem {
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if saddr == c.mem[i].addr {
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obj := c.mem[i].obj
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data := c.mem[i].data
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c.mtx.RUnlock()
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return obj, nil
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// We unmarshal object instead of using cached value to avoid possibility
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// of unintentional object corruption by caller.
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// It is safe to unmarshal without mutex, as storage under `c.mem[i].data` slices is not reused.
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obj := objectSDK.New()
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return obj, obj.Unmarshal(data)
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}
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}
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c.mtx.RUnlock()
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@ -50,18 +54,11 @@ func (c *cache) Get(addr *addressSDK.Address) (*objectSDK.Object, error) {
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//
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// Returns an error of type apistatus.ObjectNotFound if requested object is missing in write-cache.
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func (c *cache) Head(addr *addressSDK.Address) (*objectSDK.Object, error) {
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// TODO: #1149 easiest to implement solution is presented here, consider more efficient way, e.g.:
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// - provide header as common object.Object to Put, but marked to prevent correlation with full object
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// (all write-cache logic will automatically spread to headers, except flushing)
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// - cut header from in-memory objects directly and persist headers into particular bucket of DB
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// (explicit sync with full objects is needed)
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// - try to pull out binary header from binary full object (not sure if it is possible)
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obj, err := c.Get(addr)
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if err != nil {
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return nil, err
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}
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// NOTE: resetting the payload via the setter can lead to data corruption of in-memory objects, but ok for others
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return obj.CutPayload(), nil
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}
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