the pgadmin4 server could not contacted
The Application Server Could Not Be Contacted (Embedded PostgreSQL)
Issue: After upgrading the embedded PostgreSQL database from version 9.4.22 to 10.9 in version 2019.11, pgAdmin4 fails to launch on Linux platform with the error: "The application server could not be contacted."
Cause
Compared to pgAdmin3 included in PostgreSQL database version 9.4.22, pgAdmin4 included in PostgreSQL database version 10.9 is a different client executable file, which could not be executed on Linux platform.
Solution
To enable launching the new pgAdmin4 client, a startup script was added, which then requires users to run the script in order to access the client.
For Data Flow Probe
To access the client of the embedded PostgreSQL database (version 10 or later), do the following:
-
Run the following command to start the pgAdmin4 client:
$UCMDB_HOME/pgsql/pgAdmin 4/bin/start_pgadmin4.sh -
Follow the on-screen instructions and access the local web browser using URL:
http://127.0.0.1:5050 -
Log in to the client
For UCMDB Server
To access the client of the embedded PostgreSQL database (version 10 or later), do the following:
-
Run the following command to start the pgAdmin4 client:
$DATAFLOW_PROBE_HOME/pgsql/pgAdmin 4/bin/start_pgadmin4.sh -
Follow the on-screen instructions and access the local web browser using URL:
http://127.0.0.1:5050 -
Log in to the client
Quick Reference
| Environment | Startup Script |
|---|---|
| Data Flow Probe | $UCMDB_HOME/pgsql/pgAdmin 4/bin/start_pgadmin4.sh |
| UCMDB Server | $DATAFLOW_PROBE_HOME/pgsql/pgAdmin 4/bin/start_pgadmin4.sh |
Additional Notes
Version Compatibility
This issue specifically affects PostgreSQL versions 10.9 and later. Versions prior to 10.0 use pgAdmin3, which does not require this startup script.
Platform Specific
This solution is specifically for Linux platforms. Other operating systems may have different procedures for accessing pgAdmin4.
Access URL
Both environments use the same local URL: http://127.0.0.1:5050. Ensure no firewall is blocking this port.