I have a PostGIS database and a client built on top of HikariCP to read the data from a database. My client can read the data without any problem on some machines. However, on some other machines client gets stuck and is not able to read any data throwing socket timeout exceptions.
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
Before client throws SocketTimeoutException on the database side, I monitored pg_stat_activity table. The corresponding row for the query above had wait_event_type=Client and wait_event=ClientWrite. In addition, database server logged messages indicating connection is lost.
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
Versions
If I don't set socketTimeout through jdbc connection string, then connection would get stuck forever. Once the connection reaches it's max life time, it would be dropped and connected again. However, it still cannot read the data. When I set socketTimeout, then exception would be thrown.
UPDATE
If socketTimeout is not set, then pg_stat_activity table would have a row for the connection with the following values: state=idle in transaction, wait_event_type=Client and wait_event=ClientRead.
My guess is that some sort of network setting is blocking the read from the server on the client side. How can I further debug this and find the root cause?
We found out that this was caused by the database server's MTU setting. MTU was set to 9000 by default and resulted in packet loss. Changing it to 1500 resolved the issue.