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Configuration

This page lists every field of the Config passed to New, its default, and how invalid values are corrected.

Config

type Config struct {
    Redis  *Redis       `json:"redis"`
    Log    *Log         `json:"log,omitempty"`
    Option *Options     `json:"option,omitempty"`
    Email  *EmailConfig `json:"email,omitempty"`
}
Field Required When nil
Redis Yes New panics when the ping succeeds (nil pointer at sync.go:51); when the ping fails, the first file write panics
Log No All log defaults apply
Option No All option defaults apply
Email No No effect (the current version sends no mail)

When Redis is nil, initRedis fills defaults only into its local copy; the instance keeps a nil Config.Redis, and the next access to Redis.DB panics. Pass &redisFallback.Redis{} even when every default is acceptable.

Redis

Field Default Invalid values
Host localhost Empty string → localhost
Port 6379 ≤ 0 or > 65535 → 6379
Password "" —
DB 0 < 0 or > 15 → 0

DB also names the local file subdirectory {DBPath}/{DB}.

Options

Field Default Effect
DBPath ./files/redisFallback/db Root of the local JSON files; {DBPath}/{DB} must exist before startup or normal mode is never entered
MaxRetry 3 Attempts per Redis access in Get / Set; exhausting them switches to fallback
MaxQueue 1000 Fallback write queue length; when full, Set writes the file synchronously
TimeToWrite 3s Fallback batch write interval; also the maximum delay from Set to disk
TimeToCheck 1m Health-check ping interval; also the maximum delay before a recovered Redis is noticed

Any numeric field ≤ 0 falls back to its default.

Log

A type alias of Log from github.com/pardnchiu/go-logger v0.2.0:

Field Default Description
Path ./logs/redisFallback Log directory containing debug.log, output.log, error.log
Stdout false Also write to stdout
MaxSize 16 * 1024 * 1024 (16 MiB) Maximum file size in bytes
MaxBackup 5 Rotated files kept
Type text text or json

Email

EmailConfig has Host, Port, Username, Password, From, To, CC, Subject, and Body fields, but the send call is commented out in the source (sync.go:26), so setting it has no effect.

Tuning

Goal Adjustment
Return to normal mode sooner after Redis recovers Lower TimeToCheck
Lose less data if the process crashes during fallback Lower TimeToWrite
Avoid false fallback switches when Redis is flaky Raise MaxRetry (attempts have no delay between them, so the effect is limited)

Full Example

rf, err := redisFallback.New(redisFallback.Config{
    Redis: &redisFallback.Redis{
        Host:     "10.0.0.5",
        Port:     6379,
        Password: os.Getenv("REDIS_PASSWORD"),
        DB:       2,
    },
    Log: &redisFallback.Log{
        Path:   "/var/log/myapp/redis-fallback",
        Stdout: true,
    },
    Option: &redisFallback.Options{
        DBPath:      "/var/lib/myapp/redis-fallback",
        MaxRetry:    3,
        MaxQueue:    5000,
        TimeToWrite: 1 * time.Second,
        TimeToCheck: 15 * time.Second,
    },
})
if err != nil {
    log.Fatal(err)
}
defer rf.Close()
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