* fn: sync.WaitGroup replacement common.WaitGroup
agent/lb_agent/pure_runner has been incorrectly using
sync.WaitGroup semantics. Switching these components to
use the new common.WaitGroup() that provides a few handy
functionality for common graceful shutdown cases.
From https://golang.org/pkg/sync/#WaitGroup,
"Note that calls with a positive delta that occur when the counter
is zero must happen before a Wait. Calls with a negative delta,
or calls with a positive delta that start when the counter is
greater than zero, may happen at any time. Typically this means
the calls to Add should execute before the statement creating
the goroutine or other event to be waited for. If a WaitGroup
is reused to wait for several independent sets of events,
new Add calls must happen after all previous Wait calls have
returned."
HandleCallEnd introduces some complexity to the shutdowns, but this
is currently handled by AddSession(2) initially and letting the
HandleCallEnd() when to decrement by -1 in addition to decrement -1 in
Submit().
lb_agent shutdown sequence and particularly timeouts with runner pool
needs another look/revision, but this is outside of the scope of this
commit.
* fn: lb-agent wg share
* fn: no need to +2 in Submit with defer.
Removed defer since handleCallEnd already has
this responsibility.
* GRPC streams end with an EOF
The client should ensure that the final packet is followed by a GRPC
EOF. This has the benefit of permitting the client code to clean up resources.
* Don't require an entire HTTP request in RunnerCall
TryExec needs a handle on an incoming ReadCloser containing the body
of a request; however, everything else will already have been extracted
from the HTTP request in the case of lbAgent use.
(The point of this change is to simplify the interface for other uses.)
* Return error from GRPC layer explicitly
As per review
* support runner TLS certificates with specified certificate Common Names
* removes duplicate constant
* run in insecure mode by default but expose ability to create tls-secured runner pools programmatically
* fixes runner tests to use new tls interfaces
* Move out node-pool manager and replace it with RunnerPool extension
* adds extension points for runner pools in load-balanced mode
* adds error to return values in RunnerPool and Runner interfaces
* Implements runner pool contract with context-aware shutdown
* fixes issue with range
* fixes tests to use runner abstraction
* adds empty test file as a workaround for build requiring go source files in top-level package
* removes flappy timeout test
* update docs to reflect runner pool setup
* refactors system tests to use runner abstraction
* removes poolmanager
* moves runner interfaces from models to api/runnerpool package
* Adds a second runner to pool docs example
* explicitly check for request spillover to second runner in test
* moves runner pool package name for system tests
* renames runner pool pointer variable for consistency
* pass model json to runner
* automatically cast to http.ResponseWriter in load-balanced call case
* allow overriding of server RunnerPool via a programmatic ServerOption
* fixes return type of ResponseWriter in test
* move Placer interface to runnerpool package
* moves hash-based placer out of open source project
* removes siphash from Gopkg.lock
