Not all transactions are queued for broadcast

[4miners]

Expected behavior

All received transactions should be queued for broadcast.

Actual behavior

When a node receives a large number of transactions not all of them are queued for broadcast.

08:30:14.496Z  INFO lisk-framework: Transaction pool - received size: 4255 validated size: 0 verified size: 0 pending size: 25 ready size: 0
08:30:14.717Z  INFO lisk-framework: Transaction pool - received size: 4255 validated size: 1000 verified size: 25 pending size: 25 ready size: 0
08:30:14.761Z  INFO lisk-framework: Transaction pool - received size: 4255 validated size: 1000 verified size: 0 pending size: 25 ready size: 25
08:30:15.827Z  INFO lisk-framework: Transaction pool - received size: 4255 validated size: 975 verified size: 25 pending size: 25 ready size: 25
08:30:16.833Z  INFO lisk-framework: Transaction pool - received size: 4255 validated size: 950 verified size: 50 pending size: 25 ready size: 25
08:30:16.854Z  INFO lisk-framework: Transaction pool - received size: 4230 validated size: 975 verified size: 50 pending size: 25 ready size: 25
08:30:16.901Z  INFO lisk-framework: Transaction pool - received size: 4230 validated size: 950 verified size: 75 pending size: 25 ready size: 25
08:30:17.923Z  INFO lisk-framework: Transaction pool - received size: 4205 validated size: 975 verified size: 75 pending size: 25 ready size: 25
08:30:17.968Z  INFO lisk-framework: Transaction pool - received size: 4205 validated size: 950 verified size: 100 pending size: 25 ready size: 25
08:30:18.982Z  INFO lisk-framework: Transaction pool - received size: 4180 validated size: 975 verified size: 100 pending size: 25 ready size: 25
08:30:19.026Z  INFO lisk-framework: Transaction pool - received size: 4180 validated size: 950 verified size: 125 pending size: 25 ready size: 25
08:30:19.070Z DEBUG lisk-framework: Broadcasts before filtering: 930
08:30:19.650Z DEBUG lisk-framework: Broadcasts after filtering: 930
08:30:19.657Z  INFO lisk-framework: Broadcasts released: 1
08:30:19.863Z  INFO lisk-framework: Transaction pool - received size: 4155 validated size: 975 verified size: 125 pending size: 25 ready size: 25
08:30:20.049Z  INFO lisk-framework: Transaction pool - received size: 4130 validated size: 1000 verified size: 125 pending size: 25 ready size: 25
08:30:20.099Z  INFO lisk-framework: Transaction pool - received size: 4130 validated size: 975 verified size: 150 pending size: 25 ready size: 25
08:30:22.018Z  INFO lisk-framework: Transaction pool - received size: 4130 validated size: 950 verified size: 175 pending size: 25 ready size: 25
08:30:22.358Z  INFO lisk-framework: Transaction pool - received size: 4130 validated size: 950 verified size: 175 pending size: 25 ready size: 25

As you can see in this log there is large amount of transactions in the transaction pool, but only 930 are actually queued for the broadcast. When all of the queued ones are broadcasted - node doesn't queue any further transactions and all the transactions stays in the transaction pool.

08:34:43.283Z  INFO lisk-framework: Transaction pool - received size: 4960 validated size: 284 verified size: 0 pending size: 25 ready size: 25
08:34:43.347Z  INFO lisk-framework: Transaction pool - received size: 4960 validated size: 259 verified size: 25 pending size: 25 ready size: 25
08:34:43.722Z DEBUG lisk-framework: Broadcasts before filtering: 9
08:34:43.723Z DEBUG lisk-framework: Broadcasts after filtering: 9
08:34:43.726Z  INFO lisk-framework: Broadcasts released: 1
08:34:44.374Z  INFO lisk-framework: Transaction pool - received size: 4935 validated size: 284 verified size: 25 pending size: 25 ready size: 25
08:34:44.409Z  INFO lisk-framework: Transaction pool - received size: 4935 validated size: 259 verified size: 50 pending size: 25 ready size: 25

Steps to reproduce

Send to the node large amount of transactions (>2k), observe the network.

Which version(s) does this affect? (Environment, OS, etc...)

2.0.0-alpha.12