8 Commits (040f47c46e6e661c52d047258a064edc47cb431f)

Author	SHA1	Message	Date
R.B. Boyer	40336fd353	agent: fix several data races and bugs related to node-local alias checks (#5876) ... The observed bug was that a full restart of a consul datacenter (servers and clients) in conjunction with a restart of a connect-flavored application with bring-your-own-service-registration logic would very frequently cause the envoy sidecar service check to never reflect the aliased service. Over the course of investigation several bugs and unfortunate interactions were corrected: (1) local.CheckState objects were only shallow copied, but the key piece of data that gets read and updated is one of the things not copied (the underlying Check with a Status field). When the stock code was run with the race detector enabled this highly-relevant-to-the-test-scenario field was found to be racy. Changes: a) update the existing Clone method to include the Check field b) copy-on-write when those fields need to change rather than incrementally updating them in place. This made the observed behavior occur slightly less often. (2) If anything about how the runLocal method for node-local alias check logic was ever flawed, there was no fallback option. Those checks are purely edge-triggered and failure to properly notice a single edge transition would leave the alias check incorrect until the next flap of the aliased check. The change was to introduce a fallback timer to act as a control loop to double check the alias check matches the aliased check every minute (borrowing the duration from the non-local alias check logic body). This made the observed behavior eventually go away when it did occur. (3) Originally I thought there were two main actions involved in the data race: A. The act of adding the original check (from disk recovery) and its first health evaluation. B. The act of the HTTP API requests coming in and resetting the local state when re-registering the same services and checks. It took awhile for me to realize that there's a third action at work: C. The goroutines associated with the original check and the later checks. The actual sequence of actions that was causing the bad behavior was that the API actions result in the original check to be removed and re-added _without waiting for the original goroutine to terminate_. This means for brief windows of time during check definition edits there are two goroutines that can be sending updates for the alias check status. In extremely unlikely scenarios the original goroutine sees the aliased check start up in `critical` before being removed but does not get the notification about the nearly immediate update of that check to `passing`. This is interlaced wit the new goroutine coming up, initializing its base case to `passing` from the current state and then listening for new notifications of edge triggers. If the original goroutine "finishes" its update, it then commits one more write into the local state of `critical` and exits leaving the alias check no longer reflecting the underlying check. The correction here is to enforce that the old goroutines must terminate before spawning the new one for alias checks.	6 years ago
Paul Banks	e812f5516a	Add -sidecar-for and new /agent/service/:service_id endpoint (#4691) ... - A new endpoint `/v1/agent/service/:service_id` which is a generic way to look up the service for a single instance. The primary value here is that it: - **supports hash-based blocking** and so; - **replaces `/agent/connect/proxy/:proxy_id`** as the mechanism the built-in proxy uses to read its config. - It's not proxy specific and so works for any service. - It has a temporary shim to call through to the existing endpoint to preserve current managed proxy config defaulting behaviour until that is removed entirely (tested). - The built-in proxy now uses the new endpoint exclusively for it's config - The built-in proxy now has a `-sidecar-for` flag that allows the service ID of the _target_ service to be specified, on the condition that there is exactly one "sidecar" proxy (that is one that has `Proxy.DestinationServiceID` set) for the service registered. - Several fixes for edge cases for SidecarService - A fix for `Alias` checks - when running locally they didn't update their state until some external thing updated the target. If the target service has no checks registered as below, then the alias never made it past critical.	6 years ago
Mitchell Hashimoto	9a90400821	agent/checks: prevent overflow of backoff	6 years ago
Mitchell Hashimoto	f97bfd5be8	agent: address some basic feedback	6 years ago
Mitchell Hashimoto	1e9233eec1	agent/checks: set critical if RPC fails	6 years ago
Mitchell Hashimoto	e9914ee71c	agent/checks: use local state for local services	6 years ago
Mitchell Hashimoto	60c75b88da	agent/checks: reflect node failure as alias check failure	6 years ago
Mitchell Hashimoto	632e4a2c69	agent/checks: add Alias check type	6 years ago