We've updated all the places where token_metadata
is mutated, and now we can progress to the next stage
of the refactoring - gradually switching the read
code paths.
The calculate_natural_endpoints function
is at the core of all of them. It decides to what nodes
the given token should be replicated to for the given
token_metadata. It has a lot of usages in various contexts,
we can't switch them all in one commit, so instead we
allowed the function to behave in both ways. If
use_host_id parameter is false, the function uses the provided
token_metadata as is and returns endpoint_set as a result.
If it's true, it uses get_new() on the provided token_metadata
and returns host_id_set as a result.
The scope of the whole refactoring is limited to the erm data
structure, its interface will be kept inet_address based for now.
This means we'll often need to resolve host_ids to inet_address-es
as soon as we got a result from calculated_natural_endpoints.
A new calculate_natural_ips function is added for convenience.
It uses the new token_metadata and immediately resolves
returned host_id-s to inet_address-es.
The auxiliary declarations natural_ep_type, set_type, vector_type,
get_self_id, select_tm are introduced only for the sake of
migration, they will be removed later.
Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
Replace std::vector<inet_address> with a small_vector of size 3 for
replica sets (reflecting the common case of local reads, and the somewhat
less common case of single-datacenter writes). Vectors used to
describe topology changes are of size 1, reflecting that up to one
node is usually involved with topology changes. At those counts and
below we save an allocation; above those counts everything still works,
but small_vector allocates like std::vector.
In a few places we need to convert between std::vector and the new types,
but these are all out of the hot paths (or are in a hot path, but behind a
cache).
storage_proxy works with vectors of inet_addresses for replica sets
and for topology changes (pending endpoints, dead nodes). This patch
introduces new names for these (without changing the underlying
type - it's still std::vector<gms::inet_address>). This is so that
the following patch, that changes those types to utils::small_vector,
will be less noisy and highlight the real changes that take place.
