Retry query on bad connection error

Context

Imports of osm planet can take hours or days and a single error can take down the import process. Something like the database not existing or open makes sense, but a bad connection should result in retries.

[Jul  2 04:04:47] [PostGIS] SQL Error: driver: bad connection in query COPY "import"."osm_buildings" ...

Expected Behavior

On a sql error in the middle of the import, the query should be run again N times (command line flag?) with with an increasing delay between them, or a constant specified amount of time (command line flag?).

Actual Behavior

The process exists.

Possible Fix

The error handling mechanism should differentiate between fatal errors and retry-able errors. And implement a higher order function to take care of this.

func RetryN(n int, fn func(n int) error) error {
    for i := 0; i < n; i ++ {
        err := fn(i)
        if err == nil {
            return nil
        }
        log.Warnf("retry %d, %v", n, err)
    }
}

using this function might be

err := RetryN(argRetry, func(n int) error {
    _, err := sql.Query(.....)
    if err != nil {
        time.Sleep(time.Duration(n) * time.Second)
    }

    return err
}
if err != nil {
    log.Fatal(err)
}

Context

It requires re-import.

Your Environment

Version used: 0.6.0-alpha.4
Environment name and version POSTGIS="2.4.3 r16312", PostgreSQL 10.3
Server type and version: Azure database for postgres
Operating System and version: Ubuntu 18.04 LTS

omniscale / imposm3