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Extract schema migration into a separate class. (#538)
The idea is to allow several instances to exist, i.e. SetupJournalSchema and SetupSnapshotSchema.
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...a/src/main/scala/com/evolutiongaming/kafka/journal/eventual/cassandra/MigrateSchema.scala
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| package com.evolutiongaming.kafka.journal.eventual.cassandra | ||
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| import cats.MonadThrow | ||
| import cats.data.{NonEmptyList => Nel} | ||
| import cats.syntax.all._ | ||
| import com.evolutiongaming.kafka.journal.Settings | ||
| import com.evolutiongaming.kafka.journal.eventual.cassandra.CassandraHelper._ | ||
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| import scala.util.Try | ||
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| /** Migrates the existing schema to the latest version */ | ||
| trait MigrateSchema[F[_]] { | ||
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| /** Run all built-in migrations | ||
| * | ||
| * @param fresh | ||
| * Indicates if the schema was just created from scratch, or some tables were already present. The parameter is | ||
| * taken into consideration if there is no schema version information available in the settings. In this case, if | ||
| * `true`, then it will be assumed that no migrations are required, and the latest version will be saved into | ||
| * settings. If `false` then all migration steps will be attempted (because the schema, likely, was created before | ||
| * migration steps were added). | ||
| */ | ||
| def run(fresh: CreateSchema.Fresh)(implicit session: CassandraSession[F]): F[Unit] | ||
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| } | ||
| object MigrateSchema { | ||
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| /** Save version of a schema to the settings storage under specific key. | ||
| * | ||
| * @param cassandraSync | ||
| * Locking mechanism to ensure two migrations are not happening in paralell. | ||
| * @param settings | ||
| * Storage to get / save the schema version from / to. | ||
| * @param settingKey | ||
| * A key to use in a setting store. It is important to use a different key for different schemas, to ensure there | ||
| * is no accidential overwrite if both schemas are located in one keyspace. | ||
| * @param migrations | ||
| * List of CQL statements to execute. The schema version is equal to the size of this list. | ||
| * @return | ||
| * The instance of schema migrator. | ||
| */ | ||
| def forSettingKey[F[_]: MonadThrow]( | ||
| cassandraSync: CassandraSync[F], | ||
| settings: Settings[F], | ||
| settingKey: String, | ||
| migrations: Nel[String] | ||
| ): MigrateSchema[F] = new MigrateSchema[F] { | ||
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| def setVersion(version: Int) = | ||
| settings | ||
| .set(settingKey, version.toString) | ||
| .void | ||
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| def run(fresh: CreateSchema.Fresh)(implicit session: CassandraSession[F]): F[Unit] = { | ||
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| def migrate = { | ||
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| def migrate(version: Int) = { | ||
| migrations.toList | ||
| .drop(version + 1) | ||
| .toNel | ||
| .map { migrations => | ||
| migrations | ||
| .foldLeftM(version) { (version, migration) => | ||
| val version1 = version + 1 | ||
| for { | ||
| _ <- migration.execute.first.void.voidError | ||
| _ <- setVersion(version1) | ||
| } yield version1 | ||
| } | ||
| .void | ||
| } | ||
| } | ||
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| settings | ||
| .get(settingKey) | ||
| .map { setting => | ||
| setting | ||
| .flatMap { a => | ||
| Try.apply { a.value.toInt }.toOption | ||
| } | ||
| .fold { | ||
| if (fresh) { | ||
| val version = migrations.size - 1 | ||
| if (version >= 0) { | ||
| setVersion(version).some | ||
| } else { | ||
| none[F[Unit]] | ||
| } | ||
| } else { | ||
| migrate(-1) | ||
| } | ||
| } { version => | ||
| migrate(version) | ||
| } | ||
| } | ||
| } | ||
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| migrate.flatMap { migrate1 => | ||
| migrate1.foldMapM { _ => | ||
| cassandraSync { | ||
| migrate.flatMap { migrate => | ||
| migrate.foldMapM(identity) | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| } | ||
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| } | ||
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| } |
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