cli/start: write the URL file as soon as the server is ready

[knz]

Fixes #38758.

Prior to this patch, cockroach start would wait until the cluster
was initialized to write the SQL URL to the file indicated by
--listening-url-file. This contrasts with the PID file which is
written as soon as the server starts listening.

This prior behavior was motivated by the original design of the
startup routine, where the SQL server was not ready/started until the
cluster was ready.

Since then, #21682 was merged which accepts, but blocks, SQL clients
until the cluster is initialized. Since the SQL clients can now
connect as soon as the server starts listening, there is no reason
any more to wait longer.

This patch thus simplifies the code to emit the URL to the file at the
same time as the PID. This also makes it possible to use a SQL
client/command reliably as soon as the process detaches from the
terminal with --background.

Note: if you want to test the new behavior manually in an interactive
terminal, beware that the cockroach CLI client commands separately
have a connection timeout, which defaults to 5 seconds. This can be
overridden with the env var COCKROACH_CONNECT_TIMEOUT.

Release note (cli change): cockroach start now writes the client URL
to the file specified via --listen-url-file as soon as the server
is ready to accept connections. This also happens before the server
detaches from the terminal when --background is specified.

[cockroach-teamcity]

This change is 

[tbg]

bedankt!

Reviewed 6 of 6 files at r1.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @bdarnell and @knz)

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pkg/cli/start.go, line 564 at r1 (raw file):

		// If the invoker has requested an URL update, do it now that
		// the server is ready to accept SQL connections.

Can you point out why the server is ready to accept SQL connections, so that we're not scared to touch this in future rearrangements in this code?

---

pkg/cli/interactive_tests/common.tcl, line 92 at r1 (raw file):

    report "BEGIN START SERVER"
    system "$argv start-single-node --insecure --pid-file=server_pid --background -s=path=logs/db >>logs/expect-cmd.log 2>&1;
            $argv sql --insecure -e 'select 1'"

This has the COCKROACH_CONNECT_TIMEOUT default of 5s active, just pointing it out. Maybe you want to bump it preemptively because Docker.... Ditto elsewhere.

[knz]

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @bdarnell and @tbg)

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pkg/cli/start.go, line 564 at r1 (raw file):

Previously, tbg (Tobias Grieger) wrote…

Can you point out why the server is ready to accept SQL connections, so that we're not scared to touch this in future rearrangements in this code?

Done.

---

pkg/cli/interactive_tests/common.tcl, line 92 at r1 (raw file):

Previously, tbg (Tobias Grieger) wrote…

This has the COCKROACH_CONNECT_TIMEOUT default of 5s active, just pointing it out. Maybe you want to bump it preemptively because Docker.... Ditto elsewhere.

Good call. Done.

[knz]

TFYR!

bors r+

[craig]

Build succeeded

• GitHub CI (Cockroach)

[akshayjshah]

Thanks @knz!