916ec63af6
This is a new revision of the discovery server. Relevant changes and non-changes: - Protocol towards clients is unchanged. - Recommended large scale design is still to be deployed nehind nginx (I tested, and it's still a lot faster at terminating TLS). - Database backend is leveldb again, only. It scales enough, is easy to setup, and we don't need any backend to take care of. - Server supports replication. This is a simple TCP channel - protect it with a firewall when deploying over the internet. (We deploy this within the same datacenter, and with firewall.) Any incoming client announces are sent over the replication channel(s) to other peer discosrvs. Incoming replication changes are applied to the database as if they came from clients, but without the TLS/certificate overhead. - Metrics are exposed using the prometheus library, when enabled. - The database values and replication protocol is protobuf, because JSON was quite CPU intensive when I tried that and benchmarked it. - The "Retry-After" value for failed lookups gets slowly increased from a default of 120 seconds, by 5 seconds for each failed lookup, independently by each discosrv. This lowers the query load over time for clients that are never seen. The Retry-After maxes out at 3600 after a couple of weeks of this increase. The number of failed lookups is stored in the database, now and then (avoiding making each lookup a database put). All in all this means clients can be pointed towards a cluster using just multiple A / AAAA records to gain both load sharing and redundancy (if one is down, clients will talk to the remaining ones). GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4648
52 lines
1.6 KiB
Go
52 lines
1.6 KiB
Go
// Copyright 2016 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package prometheus
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import "time"
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// Timer is a helper type to time functions. Use NewTimer to create new
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// instances.
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type Timer struct {
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begin time.Time
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observer Observer
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}
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// NewTimer creates a new Timer. The provided Observer is used to observe a
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// duration in seconds. Timer is usually used to time a function call in the
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// following way:
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// func TimeMe() {
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// timer := NewTimer(myHistogram)
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// defer timer.ObserveDuration()
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// // Do actual work.
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// }
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func NewTimer(o Observer) *Timer {
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return &Timer{
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begin: time.Now(),
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observer: o,
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}
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}
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// ObserveDuration records the duration passed since the Timer was created with
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// NewTimer. It calls the Observe method of the Observer provided during
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// construction with the duration in seconds as an argument. ObserveDuration is
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// usually called with a defer statement.
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//
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// Note that this method is only guaranteed to never observe negative durations
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// if used with Go1.9+.
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func (t *Timer) ObserveDuration() {
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if t.observer != nil {
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t.observer.Observe(time.Since(t.begin).Seconds())
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}
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}
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