Question

我有一个PostGIS数据库和一个构建在HikariCP之上的客户端来读取数据库中的数据。我的客户可以毫无问题地阅读数据在某些计算机上。但是，在其他一些机器上，客户端卡住了，无法读取任何抛出套接字超时异常的数据。

MyClass:120 - Failed to execute HikariProxyPreparedStatement@2091541230 wrapping <my-query>.
org.postgresql.util.PSQLException: An I/O error occurred while sending to the backend.
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:332)
    at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:441)
    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:365)
    at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:155)
    at org.postgresql.jdbc.PgPreparedStatement.executeQuery(PgPreparedStatement.java:118)
    at com.zaxxer.hikari.pool.ProxyPreparedStatement.executeQuery(ProxyPreparedStatement.java:52)
    at com.zaxxer.hikari.pool.HikariProxyPreparedStatement.executeQuery(HikariProxyPreparedStatement.java)
    ...
Caused by: java.net.SocketTimeoutException: Read timed out
    at java.net.SocketInputStream.socketRead0(Native Method)
    at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
    at java.net.SocketInputStream.read(SocketInputStream.java:171)
    at java.net.SocketInputStream.read(SocketInputStream.java:141)
    at org.postgresql.core.VisibleBufferedInputStream.readMore(VisibleBufferedInputStream.java:140)
    at org.postgresql.core.VisibleBufferedInputStream.ensureBytes(VisibleBufferedInputStream.java:109)
    at org.postgresql.core.VisibleBufferedInputStream.read(VisibleBufferedInputStream.java:67)
    at org.postgresql.core.PGStream.receiveChar(PGStream.java:293)
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1947)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:306)
    ... 32 more

ProxyConnection:161 - HikariPool-1 - Connection org.postgresql.jdbc.PgConnection@1aafd32f marked as broken because of SQLSTATE(08006), ErrorCode(0)
org.postgresql.util.PSQLException: An I/O error occurred while sending to the backend.
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:332)
    at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:441)
    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:365)
    at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:155)
    at org.postgresql.jdbc.PgPreparedStatement.executeQuery(PgPreparedStatement.java:118)
    at com.zaxxer.hikari.pool.ProxyPreparedStatement.executeQuery(ProxyPreparedStatement.java:52)
    at com.zaxxer.hikari.pool.HikariProxyPreparedStatement.executeQuery(HikariProxyPreparedStatement.java)
    ...
Caused by: java.net.SocketTimeoutException: Read timed out
    at java.net.SocketInputStream.socketRead0(Native Method)
    at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
    at java.net.SocketInputStream.read(SocketInputStream.java:171)
    at java.net.SocketInputStream.read(SocketInputStream.java:141)
    at org.postgresql.core.VisibleBufferedInputStream.readMore(VisibleBufferedInputStream.java:140)
    at org.postgresql.core.VisibleBufferedInputStream.ensureBytes(VisibleBufferedInputStream.java:109)
    at org.postgresql.core.VisibleBufferedInputStream.read(VisibleBufferedInputStream.java:67)
    at org.postgresql.core.PGStream.receiveChar(PGStream.java:293)
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1947)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:306)
    ... 31 more

在客户端在数据库端抛出SocketTimeoutException之前，我监视了pg_stat_activity表。上面查询的相应行包含wait_event_type=Client和wait_event=ClientWrite。此外，数据库服务器记录的消息表明连接已丢失。

LOG:  unexpected EOF on client connection with an open transaction
LOG:  could not send data to client: Connection timed out
FATAL:  connection to client lost

版本

PostGIS-jdbc：2.2.1（postgresql jdbc：9.4.1208.jre7）
HikariCP：3.1.0
Postgres服务器：10.3
PostGIS服务器：2.4.4

如果我没有通过jdbc连接字符串设置socketTimeout，那么连接将永远停滞不前。一旦连接达到最大生命周期，它将被丢弃并再次连接。但是，它仍然无法读取数据。当我设置socketTimeout时，就会抛出异常。

更新如果未设置socketTimeout，则pg_stat_activity表将为具有以下值的连接添加一行：state=idle in transaction，wait_event_type=Client和wait_event=ClientRead。

我的猜测是某种网络设置阻止了客户端服务器的读取。如何进一步调试并查找根本原因？

Answer 1

我们发现这是由数据库服务器的MTU设置引起的。默认情况下，MTU设置为9000，导致数据包丢失。将其更改为1500解决了问题。

Postgres JDBC客户端在从socket读取时遇到困难

1 个答案: