Class ConnectionHandler (0.6.1)

Handles a connection from a client to Spanner. This ConnectionHandler uses WireMessage to receive and send all messages from and to the client, using the intermediate representation IntermediateStatement that servers as a middle layer between Postgres and Spanner.

Each ConnectionHandler is also a Thread. Although a TCP connection does not necessarily need to have its own thread, this makes the implementation more straightforward.

Add a currently executing statement to a buffer. This is only used in case a statement in flight is cancelled. It must be saved separately, as a new connection is spawned to issue a cancellation (as per Postgres protocol standard). This means some sort of IPC is required, which in this case is a global Map.

To be used by a cancellation command to cancel a currently running statement, as contained in a specific connection identified by connectionId. Since cancellation is a flimsy contract at best, it is not imperative that the cancellation run, but it should be attempted nonetheless.

Closes portals and statements if the result of an execute was the end of a transaction.

Clears the number of invalid messages that was received. This is called whenever a valid message is encountered.

Returns the number of invalid messages that this connection has received in a row. This can for example happen if a client has initiated a COPY operation and the copy operation fails on the server. The server will then respond with an error response, but if the client fails to read that message and continues to send copy data messages, the server could get flooded. This value is used to detect such a situation and breaks the connection if too many invalid messages in a row are received.

Reads and handles wire-protocol messages. This method is normally only called from this ConnectionHandler, but certain sub-protocols such as the COPY protocol also need to process messages in line.

Called when a Terminate message is received. This closes this ConnectionHandler.

Increases the number of invalid messages that was received in a row by 1.

Remove a statement from the buffer if it is currently executing. For more information on this use-case, read addActiveStatement comment.

Simple runner starts a loop which keeps taking inbound messages, processing them, sending them to Spanner, getting a result, processing that result, and replying to the client (in that order). Also instantiates input and output streams from the client and handles auth.