Abstract: Techniques for query execution against relational databases using connection pooling are described. According to some embodiments, a query processing service is disclosed that enables users to execute queries against target relational databases implemented by a relational database service. The service receives query requests originated by a client application at a web service endpoint and identifies a connection to a particular target database. In some examples, the query request is a Hyper Text Transfer Protocol (HTTP) message comprising a query to be executed by a target database instance within the provider network. The service transmits the query for execution at the target database via the connection and obtains a query result based on the execution of the query. The service transforms the query result into a format suitable for the client and transmits a query response to the client.

Abstract: A service provider network implements seamless scaling via proxy replay of session state. Upon a trigger, such as a determination to scale a server, a scaled server may be spun up and an identifier of the scaled server provided to a first (existing) server. The first server sends the identification of the second server, and session state information for each of the connections between the first server and the request router, to the request router. For each of the connections, the request router establishes a new connection between the request router and the second (scaled) server, and replays the session state information for the connection to the second server. The request router then routes traffic between each existing client connection (e.g., the same existing client connection which carried traffic delivered to the first server) and the corresponding new connection to the second server.

Abstract: Proxy-based scaling may be performed for databases. A proxy may be implemented for a database that can establish a connection between the proxy and a database engine to perform a database queries received from a client at the proxy. A scaling event may be detected for the database responsive to which the proxy may establish a connection with a new database engine which may, in some embodiments, have different capabilities or resources that address the features or criteria that triggered the scaling event. Session state may be copied from the database engine to the new database engine so that the new database engine may be able to provide access to the database on behalf of requests received from the client through the proxy.

Abstract: Proxy-based scaling may be performed for databases. A proxy may be implemented for a database that can establish a connection between the proxy and a database engine to perform a database queries received from a client at the proxy. A scaling event may be detected for the database responsive to which the proxy may establish a connection with a new database engine which may, in some embodiments, have different capabilities or resources that address the features or criteria that triggered the scaling event. Session state may be copied from the database engine to the new database engine so that the new database engine may be able to provide access to the database on behalf of requests received from the client through the proxy.

Abstract: A system and method for failover in a distributed system may comprise a computing device that receives client-provided information that groups computing nodes into ordered subsets. The subsets, or nodes in the subsets, may be associated with client-provided instructions for evaluating the health of a node. A node may be selected for failover based on executing the instructions and evaluating associated performance metrics. When a node is selected for failover, a replacement node may be selected based on the ordering of the subsets and the health of candidate nodes as determined based on executing the client-provided instructions.

Abstract: A dynamic proxy may be implemented for a database that can establish a connection between the proxy and a database engine to perform a database queries received from a client at the proxy. The proxy may receive a connection request (and later database queries) through a first network endpoint from a client. The proxy can then determine based on the source of the connection request a second network endpoint through which to access the database (e.g., the endpoint of the database engine). Once the proxy establishes a connection with the database engine through the second network endpoint, the proxy can request the performance of queries at the database engine instead of the client.

Abstract: A system and method for failover in a distributed system may comprise a computing device that receives information associating computing nodes with ordinal identifiers, such that the computing nodes are divided into at least a first and second subset based on the identifiers. The identifiers may further define an ordering of the subsets. When failover occurs, candidate computing nodes may be identified and selected based at least in part on the ordering. Secondary considerations, including functions performed by other members of a candidate's subset, are considered when identifying candidate nodes.

Abstract: A method and a system are provided for processing displayed text and progressively displaying results of processing the displayed text. In some embodiments, displayed text may be submitted as processing requests to process portions of the displayed text. The processing may include translation of the portions of the displayed text from a source natural language to a target natural language, grammar checking of the portions of the displayed text, or other types of processing. Each of the processing requests may include one or more complete sentences, or other units of text. Further, each of the processing requests may be submitted independently of receiving a processing response corresponding to an immediately preceding submitted processing request. Changed or annotated text included in processing responses may replace corresponding displayed text.

Abstract: A method and a system are provided for processing displayed text and progressively displaying results of processing the displayed text. In some embodiments, displayed text may be submitted as processing requests to process portions of the displayed text. The processing may include translation of the portions of the displayed text from a source natural language to a target natural language, grammar checking of the portions of the displayed text, or other types of processing. Each of the processing requests may include one or more complete sentences, or other units of text. Further, each of the processing requests may be submitted independently of receiving a processing response corresponding to an immediately preceding submitted processing request. Changed or annotated text included in processing responses may replace corresponding displayed text.