Thread: Getting error "too many clients already" despite having a db connection limit set
Getting error "too many clients already" despite having a db connection limit set
From
adolfo flores
Date:
Hello Team,
I hope you can help me with an issue we're experiencing. We have an app running on Kubernetes that opens a huge number of connections within a couple of seconds.
The database that the app connects to, is configured with a connection limit of 30% of the max_connections setting. Despite this limit being set for that database, we're seeing the following errors in the PostgreSQL logs:
FATAL: sorry, too many clients already
FATAL: remaining connection slots are reserved for roles with the SUPERUSER attribute
Is it expected behavior to reach the max_connections limit when that app opens many connections in a short period of time, even if a connection limit is set for that database and everything else uses no more than 10% of the max_connections?
Or any idea on what could be happening?
Regards.
Adolfo F.
I hope you can help me with an issue we're experiencing. We have an app running on Kubernetes that opens a huge number of connections within a couple of seconds.
The database that the app connects to, is configured with a connection limit of 30% of the max_connections setting. Despite this limit being set for that database, we're seeing the following errors in the PostgreSQL logs:
FATAL: sorry, too many clients already
FATAL: remaining connection slots are reserved for roles with the SUPERUSER attribute
Is it expected behavior to reach the max_connections limit when that app opens many connections in a short period of time, even if a connection limit is set for that database and everything else uses no more than 10% of the max_connections?
Or any idea on what could be happening?
Regards.
Adolfo F.
Re: Getting error "too many clients already" despite having a db connection limit set
From
Tom Lane
Date:
adolfo flores <adolfoflores2211@gmail.com> writes:
> I hope you can help me with an issue we're experiencing. We have an app
> running on Kubernetes that opens a huge number of connections within a
> couple of seconds.
You need to fix that app to be less unfriendly, or maybe put it behind
a connection pooler.
> Is it expected behavior to reach the max_connections limit when that app
> opens many connections in a short period of time, even if a connection
> limit is set for that database and everything else uses no more than 10% of
> the max_connections?
It takes a finite amount of time for a new backend process to figure
out which database it's supposed to connect to and then detect whether
the per-DB connection limit is exceeded. In the meantime, that
session does count against the global limit, so yeah this isn't
surprising if the connection arrival rate is high enough.
regards, tom lane
Re: Getting error "too many clients already" despite having a db connection limit set
From
Marco Torres
Date:
You might want to explore pgpool and pgbouncer. Depending in your use case you might want to glue them togeter.
On Mon, Jun 16, 2025, 10:39 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
adolfo flores <adolfoflores2211@gmail.com> writes:
> I hope you can help me with an issue we're experiencing. We have an app
> running on Kubernetes that opens a huge number of connections within a
> couple of seconds.
You need to fix that app to be less unfriendly, or maybe put it behind
a connection pooler.
> Is it expected behavior to reach the max_connections limit when that app
> opens many connections in a short period of time, even if a connection
> limit is set for that database and everything else uses no more than 10% of
> the max_connections?
It takes a finite amount of time for a new backend process to figure
out which database it's supposed to connect to and then detect whether
the per-DB connection limit is exceeded. In the meantime, that
session does count against the global limit, so yeah this isn't
surprising if the connection arrival rate is high enough.
regards, tom lane
Re: Getting error "too many clients already" despite having a db connection limit set
From
Adrian Klaver
Date:
On 6/16/25 09:29, adolfo flores wrote: > Hello Team, > > I hope you can help me with an issue we're experiencing. We have an app > running on Kubernetes that opens a huge number of connections within a > couple of seconds. > > The database that the app connects to, is configured with a connection > limit of 30% of the max_connections setting. Despite this limit being I am not understanding the above. The connection limit from the database side is going to be the value for max_connections. It is not clear to me what "... connection limit of 30% of the max_connections setting" is referring to? I suggest providing the actual numbers you are working with as well as the locations where the numbers are being set. > set for that database, we're seeing the following errors in the > PostgreSQL logs: > > FATAL: sorry, too many clients already > FATAL: remaining connection slots are reserved for roles with the > SUPERUSER attribute > > > Is it expected behavior to reach the max_connections limit when that app > opens many connections in a short period of time, even if a connection > limit is set for that database and everything else uses no more than 10% > of the max_connections? > > Or any idea on what could be happening? > > > Regards. > > Adolfo F. -- Adrian Klaver adrian.klaver@aklaver.com
Re: Getting error "too many clients already" despite having a db connection limit set
From
Adrian Klaver
Date:
On 6/16/25 11:09 AM, David G. Johnston wrote: > > > > I am not understanding the above. The connection limit from the > database > side is going to be the value for max_connections. It is not clear > to me > what "... connection limit of 30% of the max_connections setting" is > referring to? > > > See "alter database ... set" Aah, forgot about that. > > David J. > > -- Adrian Klaver adrian.klaver@aklaver.com