Lob.destroy does not release the connection immediately

[sosoba]

1. What versions are you using? 5.5.0
2. Is it an error or a hang or a crash? Error
3. What error(s) or behavior you are seeing? NJS-081: concurrent operations on a connection are disabled
4. Include a runnable Node.js script that shows the problem.

   
   import oracledb from 'oracledb';
   import { pipeline } from 'node:stream/promises';
   import { Writable } from 'node:stream';
   import { callbackify } from 'node:util';
   import { setTimeout } from 'node:timers/promises';

const failOutputStream = new Writable({ write: callbackify(async () => { await setTimeout(1); throw new Error('No left space on device'); }) });

oracledb.errorOnConcurrentExecute = true;

const conn = await oracledb.getConnection({ user: '', password: '', connectString: '', });

const {rows: [[lob]]} = await conn.execute("select lob_column from lob_table"); try { await pipeline(lob, failOutputStream); } catch (e) { console.log('Cannot copy blob to file. Reason:', e.message); }

console.log('closed:', lob.closed, 'destroyed:', lob.destroyed, 'errored:', !!lob.errored, 'inProgress:', conn._inProgress); // closed: false destroyed: true errored: true inProgress: true

await conn.execute('SELECT * FROM DUAL'); // Throws NJS-081: concurrent operations on a connection are disabled

LOB is transferred to an output stream which emits an error. The `pipeline` internally catch error from output stream and pass them to `lob.destroy(err)`. Oracledb documentation says: [This synchronous method explicitly destroys a Lob.](https://node-oracledb.readthedocs.io/en/latest/api_manual/lob.html#lob.destroy). It seems that there is internal race:

Lob waiting for next chunk and locking connection:
https://github.com/oracle/node-oracledb/blob/8388891eb59a13403d607543b578f6e7aa876da8/lib/lob.js#L106-L108

But simultaneously lob changes state to "destroyed an errored" and fire `error` event without releasing the connection: 
https://github.com/oracle/node-oracledb/blob/8388891eb59a13403d607543b578f6e7aa876da8/lib/lob.js#L81-L84

Finally `pipeline` finishes but connection are still locked and throw error next time you use it.

[anthony-tuininga]

The destroy() method is the standard stream method and not one specific to node-oracledb. It is true that node-oracledb requires the use of the connection to destroy the LOB and therefore may require a round trip and is asynchronous in nature. You can resolve the matter by using this code:

  await new Promise((resolve) => {
    lob.on('close', resolve);
    lob.destroy();
  });

I'm not sure if there is a better approach but this one certainly works!

[stale[bot]]

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