Prior to this change, prepared queries had the following behavior for
ACLs, which will need to change to support templates:
1. A management token, or a token with read access to the service being
queried needed to be provided in order to create a prepared query.
2. The token used to create the prepared query was stored with the query
in the state store and used to execute the query.
3. A management token, or the token used to create the query needed to be
supplied to perform and CRUD operations on an existing prepared query.
This was pretty subtle and complicated behavior, and won't work for
templates since the service name is computed at execution time. To solve
this, we introduce a new "prepared-query" ACL type, where the prefix
applies to the query name for static prepared query types and to the
prefix for template prepared query types.
With this change, the new behavior is:
1. A management token, or a token with "prepared-query" write access to
the query name or (soon) the given template prefix is required to do
any CRUD operations on a prepared query, or to list prepared queries
(the list is filtered by this ACL).
2. You will no longer need a management token to list prepared queries,
but you will only be able to see prepared queries that you have access
to (you get an empty list instead of permission denied).
3. When listing or getting a query, because it was easy to capture
management tokens given the past behavior, this will always blank out
the "Token" field (replacing the contents as <hidden>) for all tokens
unless a management token is supplied. Going forward, we should
discourage people from binding tokens for execution unless strictly
necessary.
4. No token will be captured by default when a prepared query is created.
If the user wishes to supply an execution token then can pass it in via
the "Token" field in the prepared query definition. Otherwise, this
field will default to empty.
5. At execution time, we will use the captured token if it exists with the
prepared query definition, otherwise we will use the token that's passed
in with the request, just like we do for other RPCs (or you can use the
agent's configured token for DNS).
6. Prepared queries with no name (accessible only by ID) will not require
ACLs to create or modify (execution time will depend on the service ACL
configuration). Our argument here is that these are designed to be
ephemeral and the IDs are as good as an ACL. Management tokens will be
able to list all of these.
These changes enable templates, but also enable delegation of authority to
manage the prepared query namespace.
Introduce a low-level background connection expiration mechanism wherein connections will be recycled periodically based on the size and health of the cluster.
For the vast majority of consul users, this will mean an average connection age of 150s. For 10K node clusters it will take ~3min for clusters to rebalance their connections. In the pathological case for a 100K cluster where 99K clients are in the minority talking to 1x server it will take ~26min to rebalance all connections.
It's possibe for clients recovering from a parititon to become fixated on a single server until the server or agent is restarted. This is of particular interest to long-running environments with stable agents, where `allow_stale` is true, and partitions occur periodically.
Increase the max idle time for agents talking to servers from 30s to 127s in order to allow for the reuse of connections that are being initiated by cron.
127s was chosen as the first prime above 120s (arbitrarily chose to use a prime) with the intent of reusing connections who are used by once-a-minute cron(8) jobs *and* who use a 60s jitter window (e.g. in vixie cron job execution can drift by up to 59s per job, or 119s for a once-a-minute cron job).
Consolidate code duplication and tests into a single lib package. Most of these functions were from various **/util.go functions that couldn't be imported due to cyclic imports. The consul/lib package is intended to be a terminal node in an import DAG and a place to stash various consul-only helper functions. Pulled in hashicorp/go-uuid instead of consolidating UUID access.
