在沒有數據庫的情況下啟動Java / Play2.5 REST API

Question

我想開始我的Java / Play！ 即使無法訪問數據庫也可以提供服務。 到目前為止，如果數據庫不可用，該服務將停止。 在Play中，是否有可能嘗試每秒重新連接一次而沒有完全停止服務並在連接可用后立即重新連接到db。

我們的application.conf當前看起來像這樣：

play.evolutions.enabled=false
//play.db.pool=bonecp

db {
   default.driver=org.postgresql.Driver
   default.url="jdbc:postgresql://postgresdb.postgres:5432/postcode"
   default.username="<username>"
   default.password="<strong-password>"
}

play.db {
  config = "db"
  prototype.hikaricp = {
    connectionTimeout = 250 milliseconds
    initializationFailFast = false
    readOnly = true
  }
}

ebean.default = ["models.*"]

目前，我得到以下日志：

2017-05-15 13:26:54.525 [error] postcode-play: Connection error: 
org.postgresql.util.PSQLException: FATAL: remaining connection slots are reserved for non-replication superuser connections
  Ort: Datei: postinit.c, Routine: InitPostgres, Zeile: 779.
  Server SQLState: 53300
    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2412)
    at org.postgresql.core.v3.QueryExecutorImpl.readStartupMessages(QueryExecutorImpl.java:2538)
    at org.postgresql.core.v3.QueryExecutorImpl.<init>(QueryExecutorImpl.java:122)
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:227)
    at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49)
    at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:194)
    at org.postgresql.Driver.makeConnection(Driver.java:431)
    at org.postgresql.Driver.connect(Driver.java:247)
    at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:95)
    at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:101)

2017-05-15 13:26:54.626 [error] postcode-play: Connection error: 
org.postgresql.util.PSQLException: FATAL: remaining connection slots are reserved for non-replication superuser connections
  Ort: Datei: postinit.c, Routine: InitPostgres, Zeile: 779.
  Server SQLState: 53300
    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2412)
    at org.postgresql.core.v3.QueryExecutorImpl.readStartupMessages(QueryExecutorImpl.java:2538)
    at org.postgresql.core.v3.QueryExecutorImpl.<init>(QueryExecutorImpl.java:122)
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:227)
    at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49)
    at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:194)
    at org.postgresql.Driver.makeConnection(Driver.java:431)
    at org.postgresql.Driver.connect(Driver.java:247)
    at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:95)
    at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:101)
.
.
.

指示服務器沒有完全停止，而是嘗試按需要多次連接到db。 但是，如果數據庫可用，則會寫入以下日志：

2017-05-15 14:08:43.748 [error] postcode-play: 

! @7430ed7gf - Internal server error, for (GET) [/?postcode=88682&country=DE] ->

play.api.Configuration$$anon$1: Configuration error[Cannot connect to database [default]]
    at play.api.Configuration$.configError(Configuration.scala:155)
    at play.api.Configuration.reportError(Configuration.scala:808)
    at play.api.db.DefaultDBApi$$anonfun$connect$1.apply(DefaultDBApi.scala:48)
    at play.api.db.DefaultDBApi$$anonfun$connect$1.apply(DefaultDBApi.scala:42)
    at scala.collection.immutable.List.foreach(List.scala:392)
    at play.api.db.DefaultDBApi.connect(DefaultDBApi.scala:42)
    at play.api.db.DBApiProvider.get$lzycompute(DBModule.scala:72)
    at play.api.db.DBApiProvider.get(DBModule.scala:62)
    at play.api.db.DBApiProvider.get(DBModule.scala:58)
    at com.google.inject.internal.ProviderInternalFactory.provision(ProviderInternalFactory.java:81)
Caused by: java.sql.SQLTransientConnectionException: HikariPool-4 - Connection is not available, request timed out after 5001ms.
    at com.zaxxer.hikari.pool.HikariPool.createTimeoutException(HikariPool.java:548)
    at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:186)
    at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:145)
    at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:83)
    at play.api.db.DefaultDatabase.getConnection(Databases.scala:142)
    at play.api.db.DefaultDatabase.getConnection(Databases.scala:138)
    at play.api.db.DefaultDBApi$$anonfun$connect$1.apply(DefaultDBApi.scala:44)
    at play.api.db.DefaultDBApi$$anonfun$connect$1.apply(DefaultDBApi.scala:42)
    at scala.collection.immutable.List.foreach(List.scala:392)
    at play.api.db.DefaultDBApi.connect(DefaultDBApi.scala:42)
Caused by: org.postgresql.util.PSQLException: Connection to localhost:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:265)
    at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49)
    at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:194)
    at org.postgresql.Driver.makeConnection(Driver.java:431)
    at org.postgresql.Driver.connect(Driver.java:247)
    at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:95)
    at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:101)
    at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:341)
    at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:193)
    at com.zaxxer.hikari.pool.HikariPool.createPoolEntry(HikariPool.java:430)
Caused by: java.net.ConnectException: Verbindungsaufbau abgelehnt (Connection refused)
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at org.postgresql.core.PGStream.<init>(PGStream.java:62)
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:144)
    at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49)
    at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:194
)

即使服務器現在可用，也無法與數據庫聯系。 如果我重新啟動服務器，將找到數據庫並且可以使用該數據庫，但是數據庫始終必須在啟動時存在。 如何解決此問題，以便可以獨立於數據庫啟動應用程序？

如果數據庫在應用程序啟動后變得不可用，則在數據庫再次變得可用之后沒有問題。 它會自動重新連接。

非常感謝您的幫助！

Answer 1

似乎您在向Postgres開放一些聯系。 這些連接必須關閉 ，否則Postgres將達到其max_connections限制。

您可以增加max_connections但不建議這樣做，因為如果設置得太高，Postgres的性能將會降低。 此外，當您使用HikariCP時，看看HikariCP文檔並不是一個壞主意，特別是idleTimeout和minimumIdle配置變量應該可以為您提供幫助。

如果上述方法不起作用，則必須確切確認與Postgres建立了多少連接。 甚至可以檢查您個人通過SSH或其他應用與Postgres進行的會話數，而不僅僅是Play框架連接數。