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token_metadata: document that update_normal_tokens is unsafe

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Currently, if token_metadata_impl::update_normal_tokens
throws an exception before it's done, it leaves the
token_metadata_impl members partially updated
and we have no way of recovering from that.

The existing use cases take that into account
and always call it on a cloned, temporary copy of the token
metadata, so if it throws, the temporary copy is tossed away
without being applied back.

So just cement this, by adding cautions in the token_metadata
class declaration.

Closes #11127

Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Message-Id: <20220728144821.130518-1-bhalevy@scylladb.com>
This commit is contained in:
Benny Halevy
2022-07-28 17:48:21 +03:00
committed by Botond Dénes
parent c3bad157e5
commit cf47db2bdb
1 changed files with 6 additions and 0 deletions
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6
locator/token_metadata.hh
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@@ -156,9 +156,15 @@ public:
const std::vector<token>& sorted_tokens() const;
// Update token->endpoint mappings for a given \c endpoint.
// \c tokens are all the tokens that are now owned by \c endpoint.
//
// Note: the function is not exception safe!
// It must be called only on a temporary copy of the token_metadata
future<> update_normal_tokens(std::unordered_set<token> tokens, inet_address endpoint);
// Batch update token->endpoint mappings for the given endpoints.
// The \c endpoint_tokens map contains the set of tokens currently owned by each respective endpoint.
//
// Note: the function is not exception safe!
// It must be called only on a temporary copy of the token_metadata
future<> update_normal_tokens(const std::unordered_map<inet_address, std::unordered_set<token>>& endpoint_tokens);
const token& first_token(const token& start) const;
size_t first_token_index(const token& start) const;