fix: allow read-only operations when all masters are down#497
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| function utils.get_spaces(vshard_router, timeout, replica_id) | ||
| local replicasets, replicaset, replicaset_id, master | ||
| local function find_any_healthy_replica_conn(replicasets) |
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https://github.com/tarantool/vshard/blob/0fd36939/vshard/replicaset.lua#L341-L362 vshard checks connections like this
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Used vshard's replica:is_connected: https://github.com/tarantool/vshard/blob/5a03168d11e717e52a89aca9b28c453e3f737be4/vshard/replicaset.lua#L1441
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| local results, err = call.map(vshard_router, CRUD_LEN_FUNC_NAME, {space_name}, { | ||
| mode = 'write', |
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Otherwise len() will fail if masters are unavailable
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Otherwise
len()will fail if masters are unavailable
may be it's ok? We need to know exact number of tuples on master. No masters -> no result.
you may add ticket for some flag for len method to get len from replicas when master is absent
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Added the read only options (mode, request_timeout, prefer_replica, balance) to allow users to explicitly fetch the length from replicas if needed.
The default behavior is unchanged (mode = 'write'), so len will still fail without masters to guarantee exact data.
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| function utils.get_space(space_name, vshard_router, timeout, replica_id) | ||
| local spaces, err, schema_version = utils.get_spaces(vshard_router, timeout, replica_id) | ||
| function utils.get_space(space_name, vshard_router, timeout, replica_id, read_only) |
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may be add timeout, replica_id, read_only args in one opts table argument?
Read-only operations (get, select, pairs, count, len, min, max) used to fail with connection errors if all masters in the cluster were unavailable, even when healthy replicas were up and failover hadn't processed yet. To resolve this, the following improvements were made: - Introduced a `read_only` flag to `utils.get_space[s]` to fetch cluster schema from any healthy replica if masters are down. - Updated `get`, `select`, `pairs`, `count`, `len`, `min`, `max` to use this new flag. - Rewrote `call.any` to iterate through all replicasets and utilize vshard's `callro` instead of `call` to fetch metadata from replicas. - Added support for `mode`, `balance`, `prefer_replica`, and `request_timeout` options in `crud.len`. The default mode remains `write` to preserve backward compatibility.
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Read-only operations (get, select, pairs, count, len, min, max) used to fail with connection errors if all masters in the cluster were unavailable, even when healthy replicas were up and failover hadn't processed yet.
To resolve this, the following improvements were made:
read_onlyflag toutils.get_space[s]to fetch cluster schema from any healthy replica if masters are down.get,select,pairs,count,len,min,maxto use this new flag.call.anyto iterate through all replicasets and utilize vshard'scallroinstead ofcallto fetch metadata from replicas.Closes TNTP-7102