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https://github.com/seaweedfs/seaweedfs.git
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Chris Lu
b18d3dc96c
Add an optional WriteCondition to CreateEntryRequest. When set, the filer evaluates it against the current entry while holding the per-path lock, so the check and the write are atomic on this filer, and returns PRECONDITION_FAILED when it does not hold. The caller must route the key's writes to the owner filer for the check to be authoritative. A condition is a list of clauses that all must hold (logical AND). One clause is the common case; several express what a single comparison cannot: an ETag set (If-Match / If-None-Match with multiple values), weak-ETag comparison, and compound conditions. ETag comparison mirrors the S3 gateway's precedence (stored Seaweed ETag attribute, then the Md5/chunk fallback) and follows RFC 7232 strong/weak rules, so results match without coupling the filer to S3 handling. Condition parsing and evaluation live in filer_grpc_server_condition.go.
97 lines
3.2 KiB
Go
97 lines
3.2 KiB
Go
package weed_server
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import (
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"strings"
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"github.com/seaweedfs/seaweedfs/weed/filer"
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"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
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"github.com/seaweedfs/seaweedfs/weed/s3api/s3_constants"
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)
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// conditionIsSet reports whether a condition asks for any check at all.
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func conditionIsSet(cond *filer_pb.WriteCondition) bool {
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return cond != nil && len(cond.Clauses) > 0
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}
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// writeConditionSatisfied reports whether the precondition holds against the
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// current entry (nil if absent), evaluated under the path lock. Every clause
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// must hold (logical AND).
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func writeConditionSatisfied(cond *filer_pb.WriteCondition, current *filer.Entry) bool {
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for _, c := range cond.Clauses {
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if !clauseSatisfied(c, current) {
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return false
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}
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}
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return true
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}
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// clauseSatisfied evaluates one primitive against the current entry. For the
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// ETag kinds, etags is a set: IF_ETAG_MATCH holds when the current ETag equals
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// any member, IF_ETAG_NOT_MATCH when it equals none.
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func clauseSatisfied(c *filer_pb.WriteCondition_Clause, current *filer.Entry) bool {
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exists := current != nil
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switch c.Kind {
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case filer_pb.WriteCondition_IF_NOT_EXISTS:
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return !exists
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case filer_pb.WriteCondition_IF_EXISTS:
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return exists
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case filer_pb.WriteCondition_IF_ETAG_MATCH:
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return exists && etagInSet(storedEntryETag(current), c.Etags, c.AllowWeak)
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case filer_pb.WriteCondition_IF_ETAG_NOT_MATCH:
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return !exists || !etagInSet(storedEntryETag(current), c.Etags, c.AllowWeak)
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case filer_pb.WriteCondition_IF_UNMODIFIED_SINCE:
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return !exists || current.Attr.Mtime.Unix() <= c.UnixTime
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case filer_pb.WriteCondition_IF_MODIFIED_SINCE:
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return !exists || current.Attr.Mtime.Unix() > c.UnixTime
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default:
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return true
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}
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}
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// etagInSet reports whether stored matches any candidate. A strong comparison
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// (allowWeak false) treats a weak ETag as never equal; a weak comparison
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// ignores the W/ marker on both sides.
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func etagInSet(stored string, candidates []string, allowWeak bool) bool {
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for _, c := range candidates {
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if etagEqual(stored, c, allowWeak) {
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return true
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}
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}
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return false
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}
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func etagEqual(stored, expected string, allowWeak bool) bool {
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sv, sWeak := canonicalETag(stored)
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ev, eWeak := canonicalETag(expected)
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// RFC 7232 strong comparison: a weak ETag on either side never matches.
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if !allowWeak && (sWeak || eWeak) {
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return false
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}
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return sv == ev
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}
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// canonicalETag splits off the weak (W/) marker before stripping quotes, so a
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// weak ETag like W/"abc" yields ("abc", true).
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func canonicalETag(etag string) (value string, weak bool) {
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etag = strings.TrimSpace(etag)
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if strings.HasPrefix(etag, "W/") {
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return strings.Trim(etag[len("W/"):], `"`), true
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}
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return strings.Trim(etag, `"`), false
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}
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// storedEntryETag mirrors the S3 gateway's ETag precedence (the stored
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// Seaweed ETag extended attribute, then the chunk/Md5 fallback) so conditional
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// comparisons match what the gateway computes, without coupling the filer to
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// S3 request handling.
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func storedEntryETag(entry *filer.Entry) string {
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if v, ok := entry.Extended[s3_constants.ExtETagKey]; ok && len(v) > 0 {
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return normalizeETag(string(v))
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}
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return normalizeETag(filer.ETagEntry(entry))
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}
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func normalizeETag(etag string) string {
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return strings.Trim(etag, `"`)
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}
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