Thread: BUG #15054: intermittent error: An I/O error occured while sending tothe backend.

The following bug has been logged on the website:

Bug reference:      15054
Logged by:          Ming Chen
Email address:      czmy@hotmail.com
PostgreSQL version: 9.3.20
Operating system:   Redhat Enterprise 6
Description:

We experienced intermittent error about "An I/O error occured while sending
to the backend" recently.

We also observed the following facts.
1. On 9.3.17, we starts to have this issue after 6000 calls (each call is a
couple of SQL queries). The chance of error is less than 0.5%.
2. After we upgrade to 9.3.18 or 9.3.20, the error happens right away (We
don't have to wait for the first 6000 calls). The chance of error is about
1%.
3. Since the error appears right away, which is less than 2 mins after
restarting Postgresql, I don't feel it is related to socket timeout (Note
that this is a RedHat system).
4. The error sometimes happened in a select statement, sometimes in an
update. I don't feel it is related the statements that we are executing.

The error detail is as follows,

Exception executing SQL "INSERT INTO .........." for task
"PreparedStatementCallback". SQLState is "08006".
org.postgresql.util.PSQLException: An I/O error occured while sending to the
backend.
    at
org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:283)
    at
org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:500)
    at
org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:388)
    at
org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:381)
    at
org.apache.commons.dbcp.DelegatingPreparedStatement.execute(DelegatingPreparedStatement.java:172)
    at
org.apache.commons.dbcp.DelegatingPreparedStatement.execute(DelegatingPreparedStatement.java:172)
    at
org.apache.commons.dbcp.DelegatingPreparedStatement.execute(DelegatingPreparedStatement.java:172).

Hi,

Our JDBC driver version is kind of outdated (9.1). But upgrading to 42.2.1 makes no difference. Still failed with around the same rate.

Restarting the DB client or DB server makes no difference.

We only have one DB client app connecting to the database. Therefore, we can't tell whether this is a general problem or not.

Could you advise how I could do to collect the server log which can contain most of the information you need to troubleshoot?

Thanks!

Ming

On Wed, Feb 7, 2018 at 7:42 AM, PG Bug reporting form <noreply@postgresql.org> wrote:

The following bug has been logged on the website:

Bug reference:      15054
Logged by:          Ming Chen
Email address:      czmy@hotmail.com
PostgreSQL version: 9.3.20
Operating system:   Redhat Enterprise 6
Description:

We experienced intermittent error about "An I/O error occured while sending
to the backend" recently.

​You will need to report your pgJDBC ​driver version and if its not the newest you should probably upgrade and confirm the problem still exists.

You say it "resets" after restarting the server...does simply reconnecting the client make a difference.  Does it afflict all connected clients or just one?

Server logs probably will be useful to examine.

David J.