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Document critical-load-hibernate-seconds

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John Nicholls 2021-12-15 16:34:05 +00:00
parent e484824bbd
commit 47fd51f804
2 changed files with 7 additions and 1 deletions
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6
doc/command-line-flags.md
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@ -63,6 +63,12 @@ Comma delimited status-name=threshold, same format as [`--max-load`](#max-load).
This may sometimes lead to migrations bailing out on a very short spike, that, while in itself is impacting production and is worth investigating, isn't reason enough to kill a 10 hour migration.
### critical-load-hibernate-seconds
When `--critical-load-hibernate-seconds` is non-zero (e.g. `--critical-load-hibernate-seconds=300`), `critical-load` does not panic and bail out; instead, `gh-ost` goes into hibernation for the specified duration. It will not read/write anything from/to any server during this time. Execution then continues upon waking from hibernation.
If `critical-load` is met again, `gh-ost` will repeat this cycle, and never panic and bail out.
### critical-load-interval-millis
When `--critical-load-interval-millis` is specified (e.g. `--critical-load-interval-millis=2500`), `gh-ost` gives a second chance: when it meets `critical-load` threshold, it doesn't bail out. Instead, it starts a timer (in this example: `2.5` seconds) and re-checks `critical-load` when the timer expires. If `critical-load` is met again, `gh-ost` panics and bails out. If not, execution continues.

2
go/cmd/gh-ost/main.go
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@ -130,7 +130,7 @@ func main() {
maxLoad := flag.String("max-load", "", "Comma delimited status-name=threshold. e.g: 'Threads_running=100,Threads_connected=500'. When status exceeds threshold, app throttles writes")
criticalLoad := flag.String("critical-load", "", "Comma delimited status-name=threshold, same format as --max-load. When status exceeds threshold, app panics and quits")
flag.Int64Var(&migrationContext.CriticalLoadIntervalMilliseconds, "critical-load-interval-millis", 0, "When 0, migration immediately bails out upon meeting critical-load. When non-zero, a second check is done after given interval, and migration only bails out if 2nd check still meets critical load")
flag.Int64Var(&migrationContext.CriticalLoadHibernateSeconds, "critical-load-hibernate-seconds", 0, "When nonzero, critical-load does not panic and bail out; instead, gh-ost goes into hibernate for the specified duration. It will not read/write anything to from/to any server")
flag.Int64Var(&migrationContext.CriticalLoadHibernateSeconds, "critical-load-hibernate-seconds", 0, "When non-zero, critical-load does not panic and bail out; instead, gh-ost goes into hibernation for the specified duration. It will not read/write anything from/to any server")
quiet := flag.Bool("quiet", false, "quiet")
verbose := flag.Bool("verbose", false, "verbose")
debug := flag.Bool("debug", false, "debug mode (very verbose)")