From: Alvaro Herrera Date: Tue, 12 Mar 2024 16:32:25 +0000 (+0100) Subject: libpq: Add encrypted and non-blocking query cancellation routines X-Git-Tag: REL_17_BETA1~666 X-Git-Url: http://git.postgresql.org/gitweb/?a=commitdiff_plain;h=61461a300c1cb5d53955ecd792ad0ce75a104736;p=postgresql.git libpq: Add encrypted and non-blocking query cancellation routines The existing PQcancel API uses blocking IO, which makes PQcancel impossible to use in an event loop based codebase without blocking the event loop until the call returns. It also doesn't encrypt the connection over which the cancel request is sent, even when the original connection required encryption. This commit adds a PQcancelConn struct and assorted functions, which provide a better mechanism of sending cancel requests; in particular all the encryption used in the original connection are also used in the cancel connection. The main entry points are: - PQcancelCreate creates the PQcancelConn based on the original connection (but does not establish an actual connection). - PQcancelStart can be used to initiate non-blocking cancel requests, using encryption if the original connection did so, which must be pumped using - PQcancelPoll. - PQcancelReset puts a PQcancelConn back in state so that it can be reused to send a new cancel request to the same connection. - PQcancelBlocking is a simpler-to-use blocking API that still uses encryption. Additional functions are - PQcancelStatus, mimicks PQstatus; - PQcancelSocket, mimicks PQcancelSocket; - PQcancelErrorMessage, mimicks PQerrorMessage; - PQcancelFinish, mimicks PQfinish. Author: Jelte Fennema-Nio Reviewed-by: Denis Laxalde Discussion: https://postgr.es/m/AM5PR83MB0178D3B31CA1B6EC4A8ECC42F7529@AM5PR83MB0178.EURPRD83.prod.outlook.com --- diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml index a2bbf33d029..d3e87056f2c 100644 --- a/doc/src/sgml/libpq.sgml +++ b/doc/src/sgml/libpq.sgml @@ -265,7 +265,7 @@ PGconn *PQsetdb(char *pghost, PQconnectStartParamsPQconnectStartParams PQconnectStartPQconnectStart - PQconnectPollPQconnectPoll + PQconnectPollPQconnectPoll nonblocking connection @@ -2622,17 +2622,19 @@ int PQserverVersion(const PGconn *conn); - PQerrorMessagePQerrorMessage + + PQerrorMessagePQerrorMessage + error messagein PGconn + - error message Returns the error message - most recently generated by an operation on the connection. + Returns the error message most recently generated by + an operation on the connection. char *PQerrorMessage(const PGconn *conn); - @@ -5287,7 +5289,7 @@ int PQisBusy(PGconn *conn); / can also attempt to cancel a command that is still being processed by the server; see . But regardless of - the return value of , the application + the return value of , the application must continue with the normal result-reading sequence using . A successful cancellation will simply cause the command to terminate sooner than it would have @@ -6030,14 +6032,429 @@ int PQsetSingleRowMode(PGconn *conn); Canceling Queries in Progress - canceling - SQL command + canceling SQL queries + + + query cancellation - - A client application can request cancellation of a command that is - still being processed by the server, using the functions described in - this section. + + Functions for Sending Cancel Requests + + + PQcancelCreatePQcancelCreate + + + + Prepares a connection over which a cancel request can be sent. + +PGcancelConn *PQcancelCreate(PGconn *conn); + + + + + creates a + PGcancelConnPGcancelConn + object, but it won't instantly start sending a cancel request over this + connection. A cancel request can be sent over this connection in a + blocking manner using and in a + non-blocking manner using . + The return value can be passed to + to check if the PGcancelConn object was + created successfully. The PGcancelConn object + is an opaque structure that is not meant to be accessed directly by the + application. This PGcancelConn object can be + used to cancel the query that's running on the original connection in a + thread-safe way. + + + + Many connection parameters of the original client will be reused when + setting up the connection for the cancel request. Importantly, if the + original connection requires encryption of the connection and/or + verification of the target host (using sslmode or + gssencmode), then the connection for the cancel + request is made with these same requirements. Any connection options + that are only used during authentication or after authentication of the + client are ignored though, because cancellation requests do not require + authentication and the connection is closed right after the cancellation + request is submitted. + + + + Note that when PQcancelCreate returns a non-null + pointer, you must call when you + are finished with it, in order to dispose of the structure and any + associated memory blocks. This must be done even if the cancel request + failed or was abandoned. + + + + + + PQcancelBlockingPQcancelBlocking + + + + Requests that the server abandons processing of the current command + in a blocking manner. + +int PQcancelBlocking(PGcancelConn *cancelConn); + + + + + The request is made over the given PGcancelConn, + which needs to be created with . + The return value of + is 1 if the cancel request was successfully + dispatched and 0 if not. If it was unsuccessful, the error message can be + retrieved using . + + + + Successful dispatch of the cancellation is no guarantee that the request + will have any effect, however. If the cancellation is effective, the + command being canceled will terminate early and return an error result. + If the cancellation fails (say, because the server was already done + processing the command), then there will be no visible result at all. + + + + + + + PQcancelStartPQcancelStart + PQcancelPollPQcancelPoll + + + + Requests that the server abandons processing of the current command + in a non-blocking manner. + +int PQcancelStart(PGcancelConn *cancelConn); + +PostgresPollingStatusType PQcancelPoll(PGcancelConn *cancelConn); + + + + + The request is made over the given PGcancelConn, + which needs to be created with . + The return value of + is 1 if the cancellation request could be started and 0 if not. + If it was unsuccessful, the error message can be + retrieved using . + + + + If PQcancelStart succeeds, the next stage + is to poll libpq so that it can proceed with + the cancel connection sequence. + Use to obtain the descriptor of the + socket underlying the database connection. + (Caution: do not assume that the socket remains the same + across PQcancelPoll calls.) + Loop thus: If PQcancelPoll(cancelConn) last returned + PGRES_POLLING_READING, wait until the socket is ready to + read (as indicated by select(), + poll(), or similar system function). + Then call PQcancelPoll(cancelConn) again. + Conversely, if PQcancelPoll(cancelConn) last returned + PGRES_POLLING_WRITING, wait until the socket is ready + to write, then call PQcancelPoll(cancelConn) again. + On the first iteration, i.e., if you have yet to call + PQcancelPoll(cancelConn), behave as if it last returned + PGRES_POLLING_WRITING. Continue this loop until + PQcancelPoll(cancelConn) returns + PGRES_POLLING_FAILED, indicating the connection procedure + has failed, or PGRES_POLLING_OK, indicating cancel + request was successfully dispatched. + + + + Successful dispatch of the cancellation is no guarantee that the request + will have any effect, however. If the cancellation is effective, the + command being canceled will terminate early and return an error result. + If the cancellation fails (say, because the server was already done + processing the command), then there will be no visible result at all. + + + + At any time during connection, the status of the connection can be + checked by calling . + If this call returns CONNECTION_BAD, then + the cancel procedure has failed; if the call returns + CONNECTION_OK, then cancel request was + successfully dispatched. + Both of these states are equally detectable from the return value of + PQcancelPoll, described above. + Other states might also occur during (and only during) an asynchronous + connection procedure. + These indicate the current stage of the connection procedure and might + be useful to provide feedback to the user for example. + These statuses are: + + + + CONNECTION_ALLOCATED + + + Waiting for a call to or + , to actually open the + socket. This is the connection state right after + calling + or . No connection to the + server has been initiated yet at this point. To actually start + sending the cancel request use or + . + + + + + + CONNECTION_STARTED + + + Waiting for connection to be made. + + + + + + CONNECTION_MADE + + + Connection OK; waiting to send. + + + + + + CONNECTION_AWAITING_RESPONSE + + + Waiting for a response from the server. + + + + + + CONNECTION_SSL_STARTUP + + + Negotiating SSL encryption. + + + + + + CONNECTION_GSS_STARTUP + + + Negotiating GSS encryption. + + + + + + Note that, although these constants will remain (in order to maintain + compatibility), an application should never rely upon these occurring in a + particular order, or at all, or on the status always being one of these + documented values. An application might do something like this: + +switch(PQcancelStatus(conn)) +{ + case CONNECTION_STARTED: + feedback = "Connecting..."; + break; + + case CONNECTION_MADE: + feedback = "Connected to server..."; + break; +. +. +. + default: + feedback = "Connecting..."; +} + + + + + The connect_timeout connection parameter is ignored + when using PQcancelPoll; it is the application's + responsibility to decide whether an excessive amount of time has elapsed. + Otherwise, PQcancelStart followed by a + PQcancelPoll loop is equivalent to + . + + + + + + + PQcancelStatusPQcancelStatus + + + + Returns the status of the cancel connection. + +ConnStatusType PQcancelStatus(const PGcancelConn *cancelConn); + + + + + The status can be one of a number of values. However, only three of + these are seen outside of an asynchronous cancel procedure: + CONNECTION_ALLOCATED, + CONNECTION_OK and + CONNECTION_BAD. The initial state of a + PGcancelConn that's successfully created using + is CONNECTION_ALLOCATED. + A cancel request that was successfully dispatched + has the status CONNECTION_OK. A failed + cancel attempt is signaled by status + CONNECTION_BAD. An OK status will + remain so until or + is called. + + + + See the entry for with regards + to other status codes that might be returned. + + + + Successful dispatch of the cancellation is no guarantee that the request + will have any effect, however. If the cancellation is effective, the + command being canceled will terminate early and return an error result. + If the cancellation fails (say, because the server was already done + processing the command), then there will be no visible result at all. + + + + + + + PQcancelSocketPQcancelSocket + + + + Obtains the file descriptor number of the cancel connection socket to + the server. + +int PQcancelSocket(const PGcancelConn *cancelConn); + + + + + A valid descriptor will be greater than or equal to 0; + a result of -1 indicates that no server connection is currently open. + This might change as a result of calling any of the functions + in this section on the PQcancelConn + (except for and + PQcancelSocket itself). + + + + + + + PQcancelErrorMessagePQcancelErrorMessage + error messagein PGcancelConn + + + + + Returns the error message most recently generated by an + operation on the cancel connection. + +char *PQcancelErrorMessage(const PGcancelConn *cancelconn); + + + + + Nearly all libpq functions that take a + PGcancelConn will set a message for + if they fail. + Note that by libpq convention, + a nonempty result + can consist of multiple lines, and will include a trailing newline. + The caller should not free the result directly. + It will be freed when the associated + PGcancelConn handle is passed to + . The result string should not be + expected to remain the same across operations on the + PGcancelConn structure. + + + + + + PQcancelFinishPQcancelFinish + + + Closes the cancel connection (if it did not finish sending the + cancel request yet). Also frees memory used by the + PGcancelConn object. + +void PQcancelFinish(PGcancelConn *cancelConn); + + + + + Note that even if the cancel attempt fails (as + indicated by ), the + application should call + to free the memory used by the PGcancelConn + object. + The PGcancelConn pointer must not be used + again after has been called. + + + + + + PQcancelResetPQcancelReset + + + Resets the PGcancelConn so it can be reused for a new + cancel connection. + +void PQcancelReset(PGcancelConn *cancelConn); + + + + + If the PGcancelConn is currently used to send a cancel + request, then this connection is closed. It will then prepare the + PGcancelConn object such that it can be used to send a + new cancel request. + + + + This can be used to create one PGcancelConn + for a PGconn and reuse it multiple times + throughout the lifetime of the original PGconn. + + + + + + + + Obsolete Functions for Sending Cancel Requests + + + These functions represent older methods of sending cancel requests. + Although they still work, they are deprecated due to not sending the cancel + requests in an encrypted manner, even when the original connection + specified sslmode or gssencmode to + require encryption. Thus these older methods are heavily discouraged from + being used in new code, and it is recommended to change existing code to + use the new functions instead. + @@ -6046,7 +6463,7 @@ int PQsetSingleRowMode(PGconn *conn); Creates a data structure containing the information needed to cancel - a command issued through a particular database connection. + a command using . PGcancel *PQgetCancel(PGconn *conn); @@ -6054,10 +6471,11 @@ PGcancel *PQgetCancel(PGconn *conn); creates a - PGcancelPGcancel object - given a PGconn connection object. It will return - NULL if the given conn is NULL or an invalid - connection. The PGcancel object is an opaque + PGcancelPGcancel + object given a PGconn connection object. + It will return NULL if the given conn + is NULL or an invalid connection. + The PGcancel object is an opaque structure that is not meant to be accessed directly by the application; it can only be passed to or . @@ -6088,36 +6506,38 @@ void PQfreeCancel(PGcancel *cancel); - Requests that the server abandon processing of the current command. + is a deprecated and insecure + variant of , but one that can be + used safely from within a signal handler. int PQcancel(PGcancel *cancel, char *errbuf, int errbufsize); - The return value is 1 if the cancel request was successfully - dispatched and 0 if not. If not, errbuf is filled - with an explanatory error message. errbuf - must be a char array of size errbufsize (the - recommended size is 256 bytes). + only exists because of backwards + compatibility reasons. should be + used instead. The only benefit that has + is that it can be safely invoked from a signal handler, if the + errbuf is a local variable in the signal handler. + However, this is generally not considered a big enough benefit to be + worth the security issues that this function has. - Successful dispatch is no guarantee that the request will have - any effect, however. If the cancellation is effective, the current - command will terminate early and return an error result. If the - cancellation fails (say, because the server was already done - processing the command), then there will be no visible result at - all. + The PGcancel object is read-only as far as + is concerned, so it can also be invoked + from a thread that is separate from the one manipulating the + PGconn object. - can safely be invoked from a signal - handler, if the errbuf is a local variable in the - signal handler. The PGcancel object is read-only - as far as is concerned, so it can - also be invoked from a thread that is separate from the one - manipulating the PGconn object. + The return value of is 1 if the + cancel request was successfully dispatched and 0 if not. + If not, errbuf is filled with an explanatory + error message. + errbuf must be a char array of size + errbufsize (the recommended size is 256 bytes). @@ -6129,13 +6549,21 @@ int PQcancel(PGcancel *cancel, char *errbuf, int errbufsize); - is a deprecated variant of - . + is a deprecated and insecure + variant of . int PQrequestCancel(PGconn *conn); + + only exists because of backwards + compatibility reasons. should be + used instead. There is no benefit to using + over + . + + Requests that the server abandon processing of the current command. It operates directly on the @@ -6150,8 +6578,7 @@ int PQrequestCancel(PGconn *conn); - - + @@ -9362,7 +9789,7 @@ int PQisthreadsafe(); The deprecated functions and are not thread-safe and should not be used in multithread programs. - can be replaced by . + can be replaced by . can be replaced by . diff --git a/src/interfaces/libpq/exports.txt b/src/interfaces/libpq/exports.txt index 088592deb16..9fbd3d34074 100644 --- a/src/interfaces/libpq/exports.txt +++ b/src/interfaces/libpq/exports.txt @@ -193,3 +193,12 @@ PQsendClosePrepared 190 PQsendClosePortal 191 PQchangePassword 192 PQsendPipelineSync 193 +PQcancelBlocking 194 +PQcancelStart 195 +PQcancelCreate 196 +PQcancelPoll 197 +PQcancelStatus 198 +PQcancelSocket 199 +PQcancelErrorMessage 200 +PQcancelReset 201 +PQcancelFinish 202 diff --git a/src/interfaces/libpq/fe-cancel.c b/src/interfaces/libpq/fe-cancel.c index d69b8f9f9f4..6bbd126bafe 100644 --- a/src/interfaces/libpq/fe-cancel.c +++ b/src/interfaces/libpq/fe-cancel.c @@ -22,6 +22,17 @@ #include "port/pg_bswap.h" +/* + * pg_cancel_conn (backing struct for PGcancelConn) is a wrapper around a + * PGconn to send cancellations using PQcancelBlocking and PQcancelStart. + * This isn't just a typedef because we want the compiler to complain when a + * PGconn is passed to a function that expects a PGcancelConn, and vice versa. + */ +struct pg_cancel_conn +{ + PGconn conn; +}; + /* * pg_cancel (backing struct for PGcancel) stores all data necessary to send a * cancel request. @@ -41,6 +52,289 @@ struct pg_cancel }; +/* + * PQcancelCreate + * + * Create and return a PGcancelConn, which can be used to securely cancel a + * query on the given connection. + * + * This requires either following the non-blocking flow through + * PQcancelStart() and PQcancelPoll(), or the blocking PQcancelBlocking(). + */ +PGcancelConn * +PQcancelCreate(PGconn *conn) +{ + PGconn *cancelConn = pqMakeEmptyPGconn(); + pg_conn_host originalHost; + + if (cancelConn == NULL) + return NULL; + + /* Check we have an open connection */ + if (!conn) + { + libpq_append_conn_error(cancelConn, "passed connection was NULL"); + return (PGcancelConn *) cancelConn; + } + + if (conn->sock == PGINVALID_SOCKET) + { + libpq_append_conn_error(cancelConn, "passed connection is not open"); + return (PGcancelConn *) cancelConn; + } + + /* + * Indicate that this connection is used to send a cancellation + */ + cancelConn->cancelRequest = true; + + if (!pqCopyPGconn(conn, cancelConn)) + return (PGcancelConn *) cancelConn; + + /* + * Compute derived options + */ + if (!pqConnectOptions2(cancelConn)) + return (PGcancelConn *) cancelConn; + + /* + * Copy cancellation token data from the original connnection + */ + cancelConn->be_pid = conn->be_pid; + cancelConn->be_key = conn->be_key; + + /* + * Cancel requests should not iterate over all possible hosts. The request + * needs to be sent to the exact host and address that the original + * connection used. So we manually create the host and address arrays with + * a single element after freeing the host array that we generated from + * the connection options. + */ + pqReleaseConnHosts(cancelConn); + cancelConn->nconnhost = 1; + cancelConn->naddr = 1; + + cancelConn->connhost = calloc(cancelConn->nconnhost, sizeof(pg_conn_host)); + if (!cancelConn->connhost) + goto oom_error; + + originalHost = conn->connhost[conn->whichhost]; + if (originalHost.host) + { + cancelConn->connhost[0].host = strdup(originalHost.host); + if (!cancelConn->connhost[0].host) + goto oom_error; + } + if (originalHost.hostaddr) + { + cancelConn->connhost[0].hostaddr = strdup(originalHost.hostaddr); + if (!cancelConn->connhost[0].hostaddr) + goto oom_error; + } + if (originalHost.port) + { + cancelConn->connhost[0].port = strdup(originalHost.port); + if (!cancelConn->connhost[0].port) + goto oom_error; + } + if (originalHost.password) + { + cancelConn->connhost[0].password = strdup(originalHost.password); + if (!cancelConn->connhost[0].password) + goto oom_error; + } + + cancelConn->addr = calloc(cancelConn->naddr, sizeof(AddrInfo)); + if (!cancelConn->connhost) + goto oom_error; + + cancelConn->addr[0].addr = conn->raddr; + cancelConn->addr[0].family = conn->raddr.addr.ss_family; + + cancelConn->status = CONNECTION_ALLOCATED; + return (PGcancelConn *) cancelConn; + +oom_error: + conn->status = CONNECTION_BAD; + libpq_append_conn_error(cancelConn, "out of memory"); + return (PGcancelConn *) cancelConn; +} + + +/* + * PQcancelBlocking + * + * Send a cancellation request in a blocking fashion. + * Returns 1 if successful 0 if not. + */ +int +PQcancelBlocking(PGcancelConn *cancelConn) +{ + if (!PQcancelStart(cancelConn)) + return 0; + return pqConnectDBComplete(&cancelConn->conn); +} + +/* + * PQcancelStart + * + * Starts sending a cancellation request in a non-blocking fashion. Returns + * 1 if successful 0 if not. + */ +int +PQcancelStart(PGcancelConn *cancelConn) +{ + if (!cancelConn || cancelConn->conn.status == CONNECTION_BAD) + return 0; + + if (cancelConn->conn.status != CONNECTION_ALLOCATED) + { + libpq_append_conn_error(&cancelConn->conn, + "cancel request is already being sent on this connection"); + cancelConn->conn.status = CONNECTION_BAD; + return 0; + } + + return pqConnectDBStart(&cancelConn->conn); +} + +/* + * PQcancelPoll + * + * Poll a cancel connection. For usage details see PQconnectPoll. + */ +PostgresPollingStatusType +PQcancelPoll(PGcancelConn *cancelConn) +{ + PGconn *conn = &cancelConn->conn; + int n; + + /* + * We leave most of the connection establishement to PQconnectPoll, since + * it's very similar to normal connection establishment. But once we get + * to the CONNECTION_AWAITING_RESPONSE we need to start doing our own + * thing. + */ + if (conn->status != CONNECTION_AWAITING_RESPONSE) + { + return PQconnectPoll(conn); + } + + /* + * At this point we are waiting on the server to close the connection, + * which is its way of communicating that the cancel has been handled. + */ + + n = pqReadData(conn); + + if (n == 0) + return PGRES_POLLING_READING; + +#ifndef WIN32 + + /* + * If we receive an error report it, but only if errno is non-zero. + * Otherwise we assume it's an EOF, which is what we expect from the + * server. + * + * We skip this for Windows, because Windows is a bit special in its EOF + * behaviour for TCP. Sometimes it will error with an ECONNRESET when + * there is a clean connection closure. See these threads for details: + * https://www.postgresql.org/message-id/flat/90b34057-4176-7bb0-0dbb-9822a5f6425b%40greiz-reinsdorf.de + * + * https://www.postgresql.org/message-id/flat/CA%2BhUKG%2BOeoETZQ%3DQw5Ub5h3tmwQhBmDA%3DnuNO3KG%3DzWfUypFAw%40mail.gmail.com + * + * PQcancel ignores such errors and reports success for the cancellation + * anyway, so even if this is not always correct we do the same here. + */ + if (n < 0 && errno != 0) + { + conn->status = CONNECTION_BAD; + return PGRES_POLLING_FAILED; + } +#endif + + /* + * We don't expect any data, only connection closure. So if we strangely + * do receive some data we consider that an error. + */ + if (n > 0) + { + libpq_append_conn_error(conn, "received unexpected response from server"); + conn->status = CONNECTION_BAD; + return PGRES_POLLING_FAILED; + } + + /* + * Getting here means that we received an EOF, which is what we were + * expecting -- the cancel request has completed. + */ + cancelConn->conn.status = CONNECTION_OK; + resetPQExpBuffer(&conn->errorMessage); + return PGRES_POLLING_OK; +} + +/* + * PQcancelStatus + * + * Get the status of a cancel connection. + */ +ConnStatusType +PQcancelStatus(const PGcancelConn *cancelConn) +{ + return PQstatus(&cancelConn->conn); +} + +/* + * PQcancelSocket + * + * Get the socket of the cancel connection. + */ +int +PQcancelSocket(const PGcancelConn *cancelConn) +{ + return PQsocket(&cancelConn->conn); +} + +/* + * PQcancelErrorMessage + * + * Get the socket of the cancel connection. + */ +char * +PQcancelErrorMessage(const PGcancelConn *cancelConn) +{ + return PQerrorMessage(&cancelConn->conn); +} + +/* + * PQcancelReset + * + * Resets the cancel connection, so it can be reused to send a new cancel + * request. + */ +void +PQcancelReset(PGcancelConn *cancelConn) +{ + pqClosePGconn(&cancelConn->conn); + cancelConn->conn.status = CONNECTION_ALLOCATED; + cancelConn->conn.whichhost = 0; + cancelConn->conn.whichaddr = 0; + cancelConn->conn.try_next_host = false; + cancelConn->conn.try_next_addr = false; +} + +/* + * PQcancelFinish + * + * Closes and frees the cancel connection. + */ +void +PQcancelFinish(PGcancelConn *cancelConn) +{ + PQfinish(&cancelConn->conn); +} + /* * PQgetCancel: get a PGcancel structure corresponding to a connection. * @@ -145,7 +439,7 @@ optional_setsockopt(int fd, int protoid, int optid, int value) /* - * PQcancel: request query cancel + * PQcancel: old, non-encrypted, but signal-safe way of requesting query cancel * * The return value is true if the cancel request was successfully * dispatched, false if not (in which case an error message is available). diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c index d4e10a0c4f3..01e49c6975e 100644 --- a/src/interfaces/libpq/fe-connect.c +++ b/src/interfaces/libpq/fe-connect.c @@ -616,8 +616,17 @@ pqDropServerData(PGconn *conn) conn->write_failed = false; free(conn->write_err_msg); conn->write_err_msg = NULL; - conn->be_pid = 0; - conn->be_key = 0; + + /* + * Cancel connections need to retain their be_pid and be_key across + * PQcancelReset invocations, otherwise they would not have access to the + * secret token of the connection they are supposed to cancel. + */ + if (!conn->cancelRequest) + { + conn->be_pid = 0; + conn->be_key = 0; + } } @@ -923,6 +932,45 @@ fillPGconn(PGconn *conn, PQconninfoOption *connOptions) return true; } +/* + * Copy over option values from srcConn to dstConn + * + * Don't put anything cute here --- intelligence should be in + * connectOptions2 ... + * + * Returns true on success. On failure, returns false and sets error message of + * dstConn. + */ +bool +pqCopyPGconn(PGconn *srcConn, PGconn *dstConn) +{ + const internalPQconninfoOption *option; + + /* copy over connection options */ + for (option = PQconninfoOptions; option->keyword; option++) + { + if (option->connofs >= 0) + { + const char **tmp = (const char **) ((char *) srcConn + option->connofs); + + if (*tmp) + { + char **dstConnmember = (char **) ((char *) dstConn + option->connofs); + + if (*dstConnmember) + free(*dstConnmember); + *dstConnmember = strdup(*tmp); + if (*dstConnmember == NULL) + { + libpq_append_conn_error(dstConn, "out of memory"); + return false; + } + } + } + } + return true; +} + /* * connectOptions1 * @@ -2308,10 +2356,18 @@ pqConnectDBStart(PGconn *conn) * Set up to try to connect to the first host. (Setting whichhost = -1 is * a bit of a cheat, but PQconnectPoll will advance it to 0 before * anything else looks at it.) + * + * Cancel requests are special though, they should only try one host and + * address, and these fields have already been set up in PQcancelCreate, + * so leave these fields alone for cancel requests. */ - conn->whichhost = -1; - conn->try_next_addr = false; - conn->try_next_host = true; + if (!conn->cancelRequest) + { + conn->whichhost = -1; + conn->try_next_host = true; + conn->try_next_addr = false; + } + conn->status = CONNECTION_NEEDED; /* Also reset the target_server_type state if needed */ @@ -2453,7 +2509,10 @@ pqConnectDBComplete(PGconn *conn) /* * Now try to advance the state machine. */ - flag = PQconnectPoll(conn); + if (conn->cancelRequest) + flag = PQcancelPoll((PGcancelConn *) conn); + else + flag = PQconnectPoll(conn); } } @@ -2578,13 +2637,17 @@ keep_going: /* We will come back to here until there is * Oops, no more hosts. * * If we are trying to connect in "prefer-standby" mode, then drop - * the standby requirement and start over. + * the standby requirement and start over. Don't do this for + * cancel requests though, since we are certain the list of + * servers won't change as the target_server_type option is not + * applicable to those connections. * * Otherwise, an appropriate error message is already set up, so * we just need to set the right status. */ if (conn->target_server_type == SERVER_TYPE_PREFER_STANDBY && - conn->nconnhost > 0) + conn->nconnhost > 0 && + !conn->cancelRequest) { conn->target_server_type = SERVER_TYPE_PREFER_STANDBY_PASS2; conn->whichhost = 0; @@ -3226,6 +3289,29 @@ keep_going: /* We will come back to here until there is } #endif /* USE_SSL */ + /* + * For cancel requests this is as far as we need to go in the + * connection establishment. Now we can actually send our + * cancellation request. + */ + if (conn->cancelRequest) + { + CancelRequestPacket cancelpacket; + + packetlen = sizeof(cancelpacket); + cancelpacket.cancelRequestCode = (MsgType) pg_hton32(CANCEL_REQUEST_CODE); + cancelpacket.backendPID = pg_hton32(conn->be_pid); + cancelpacket.cancelAuthCode = pg_hton32(conn->be_key); + if (pqPacketSend(conn, 0, &cancelpacket, packetlen) != STATUS_OK) + { + libpq_append_conn_error(conn, "could not send cancel packet: %s", + SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf))); + goto error_return; + } + conn->status = CONNECTION_AWAITING_RESPONSE; + return PGRES_POLLING_READING; + } + /* * Build the startup packet. */ @@ -3975,8 +4061,14 @@ keep_going: /* We will come back to here until there is } } - /* We can release the address list now. */ - release_conn_addrinfo(conn); + /* + * For non cancel requests we can release the address list + * now. For cancel requests we never actually resolve + * addresses and instead the addrinfo exists for the lifetime + * of the connection. + */ + if (!conn->cancelRequest) + release_conn_addrinfo(conn); /* * Contents of conn->errorMessage are no longer interesting @@ -4344,6 +4436,7 @@ freePGconn(PGconn *conn) free(conn->events[i].name); } + release_conn_addrinfo(conn); pqReleaseConnHosts(conn); free(conn->client_encoding_initial); @@ -4495,6 +4588,13 @@ release_conn_addrinfo(PGconn *conn) static void sendTerminateConn(PGconn *conn) { + /* + * The Postgres cancellation protocol does not have a notion of a + * Terminate message, so don't send one. + */ + if (conn->cancelRequest) + return; + /* * Note that the protocol doesn't allow us to send Terminate messages * during the startup phase. @@ -4548,7 +4648,14 @@ pqClosePGconn(PGconn *conn) conn->pipelineStatus = PQ_PIPELINE_OFF; pqClearAsyncResult(conn); /* deallocate result */ pqClearConnErrorState(conn); - release_conn_addrinfo(conn); + + /* + * Release addrinfo, but since cancel requests never change their addrinfo + * we don't do that. Otherwise we would have to rebuild it during a + * PQcancelReset. + */ + if (!conn->cancelRequest) + release_conn_addrinfo(conn); /* Reset all state obtained from server, too */ pqDropServerData(conn); diff --git a/src/interfaces/libpq/libpq-fe.h b/src/interfaces/libpq/libpq-fe.h index 2c06044a75e..09b485bd2bc 100644 --- a/src/interfaces/libpq/libpq-fe.h +++ b/src/interfaces/libpq/libpq-fe.h @@ -79,7 +79,9 @@ typedef enum CONNECTION_GSS_STARTUP, /* Negotiating GSSAPI. */ CONNECTION_CHECK_TARGET, /* Internal state: checking target server * properties. */ - CONNECTION_CHECK_STANDBY /* Checking if server is in standby mode. */ + CONNECTION_CHECK_STANDBY, /* Checking if server is in standby mode. */ + CONNECTION_ALLOCATED /* Waiting for connection attempt to be + * started. */ } ConnStatusType; typedef enum @@ -166,6 +168,11 @@ typedef enum */ typedef struct pg_conn PGconn; +/* PGcancelConn encapsulates a cancel connection to the backend. + * The contents of this struct are not supposed to be known to applications. + */ +typedef struct pg_cancel_conn PGcancelConn; + /* PGresult encapsulates the result of a query (or more precisely, of a single * SQL command --- a query string given to PQsendQuery can contain multiple * commands and thus return multiple PGresult objects). @@ -322,16 +329,34 @@ extern PostgresPollingStatusType PQresetPoll(PGconn *conn); /* Synchronous (blocking) */ extern void PQreset(PGconn *conn); +/* Create a PGcancelConn that's used to cancel a query on the given PGconn */ +extern PGcancelConn *PQcancelCreate(PGconn *conn); + +/* issue a cancel request in a non-blocking manner */ +extern int PQcancelStart(PGcancelConn *cancelConn); + +/* issue a blocking cancel request */ +extern int PQcancelBlocking(PGcancelConn *cancelConn); + +/* poll a non-blocking cancel request */ +extern PostgresPollingStatusType PQcancelPoll(PGcancelConn *cancelConn); +extern ConnStatusType PQcancelStatus(const PGcancelConn *cancelConn); +extern int PQcancelSocket(const PGcancelConn *cancelConn); +extern char *PQcancelErrorMessage(const PGcancelConn *cancelConn); +extern void PQcancelReset(PGcancelConn *cancelConn); +extern void PQcancelFinish(PGcancelConn *cancelConn); + + /* request a cancel structure */ extern PGcancel *PQgetCancel(PGconn *conn); /* free a cancel structure */ extern void PQfreeCancel(PGcancel *cancel); -/* issue a cancel request */ +/* deprecated version of PQcancelBlocking, but one which is signal-safe */ extern int PQcancel(PGcancel *cancel, char *errbuf, int errbufsize); -/* backwards compatible version of PQcancel; not thread-safe */ +/* deprecated version of PQcancel; not thread-safe */ extern int PQrequestCancel(PGconn *conn); /* Accessor functions for PGconn objects */ diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h index 3abcd180d6d..9c05f11a6e9 100644 --- a/src/interfaces/libpq/libpq-int.h +++ b/src/interfaces/libpq/libpq-int.h @@ -409,6 +409,10 @@ struct pg_conn char *require_auth; /* name of the expected auth method */ char *load_balance_hosts; /* load balance over hosts */ + bool cancelRequest; /* true if this connection is used to send a + * cancel request, instead of being a normal + * connection that's used for queries */ + /* Optional file to write trace info to */ FILE *Pfdebug; int traceFlags; @@ -669,6 +673,7 @@ extern void pqClosePGconn(PGconn *conn); extern int pqPacketSend(PGconn *conn, char pack_type, const void *buf, size_t buf_len); extern bool pqGetHomeDirectory(char *buf, int bufsize); +extern bool pqCopyPGconn(PGconn *srcConn, PGconn *dstConn); extern bool pqParseIntParam(const char *value, int *result, PGconn *conn, const char *context); diff --git a/src/test/modules/libpq_pipeline/libpq_pipeline.c b/src/test/modules/libpq_pipeline/libpq_pipeline.c index c6c7b1c3a17..1fe15ee8899 100644 --- a/src/test/modules/libpq_pipeline/libpq_pipeline.c +++ b/src/test/modules/libpq_pipeline/libpq_pipeline.c @@ -215,6 +215,7 @@ static void test_cancel(PGconn *conn) { PGcancel *cancel; + PGcancelConn *cancelConn; PGconn *monitorConn; char errorbuf[256]; @@ -251,6 +252,126 @@ test_cancel(PGconn *conn) pg_fatal("failed to run PQrequestCancel: %s", PQerrorMessage(conn)); confirm_query_canceled(conn); + /* test PQcancelBlocking */ + send_cancellable_query(conn, monitorConn); + cancelConn = PQcancelCreate(conn); + if (!PQcancelBlocking(cancelConn)) + pg_fatal("failed to run PQcancelBlocking: %s", PQcancelErrorMessage(cancelConn)); + confirm_query_canceled(conn); + PQcancelFinish(cancelConn); + + /* test PQcancelCreate and then polling with PQcancelPoll */ + send_cancellable_query(conn, monitorConn); + cancelConn = PQcancelCreate(conn); + if (!PQcancelStart(cancelConn)) + pg_fatal("bad cancel connection: %s", PQcancelErrorMessage(cancelConn)); + while (true) + { + struct timeval tv; + fd_set input_mask; + fd_set output_mask; + PostgresPollingStatusType pollres = PQcancelPoll(cancelConn); + int sock = PQcancelSocket(cancelConn); + + if (pollres == PGRES_POLLING_OK) + break; + + FD_ZERO(&input_mask); + FD_ZERO(&output_mask); + switch (pollres) + { + case PGRES_POLLING_READING: + pg_debug("polling for reads\n"); + FD_SET(sock, &input_mask); + break; + case PGRES_POLLING_WRITING: + pg_debug("polling for writes\n"); + FD_SET(sock, &output_mask); + break; + default: + pg_fatal("bad cancel connection: %s", PQcancelErrorMessage(cancelConn)); + } + + if (sock < 0) + pg_fatal("sock did not exist: %s", PQcancelErrorMessage(cancelConn)); + + tv.tv_sec = 3; + tv.tv_usec = 0; + + while (true) + { + if (select(sock + 1, &input_mask, &output_mask, NULL, &tv) < 0) + { + if (errno == EINTR) + continue; + pg_fatal("select() failed: %m"); + } + break; + } + } + if (PQcancelStatus(cancelConn) != CONNECTION_OK) + pg_fatal("unexpected cancel connection status: %s", PQcancelErrorMessage(cancelConn)); + confirm_query_canceled(conn); + + /* + * test PQcancelReset works on the cancel connection and it can be reused + * afterwards + */ + PQcancelReset(cancelConn); + + send_cancellable_query(conn, monitorConn); + if (!PQcancelStart(cancelConn)) + pg_fatal("bad cancel connection: %s", PQcancelErrorMessage(cancelConn)); + while (true) + { + struct timeval tv; + fd_set input_mask; + fd_set output_mask; + PostgresPollingStatusType pollres = PQcancelPoll(cancelConn); + int sock = PQcancelSocket(cancelConn); + + if (pollres == PGRES_POLLING_OK) + break; + + FD_ZERO(&input_mask); + FD_ZERO(&output_mask); + switch (pollres) + { + case PGRES_POLLING_READING: + pg_debug("polling for reads\n"); + FD_SET(sock, &input_mask); + break; + case PGRES_POLLING_WRITING: + pg_debug("polling for writes\n"); + FD_SET(sock, &output_mask); + break; + default: + pg_fatal("bad cancel connection: %s", PQcancelErrorMessage(cancelConn)); + } + + if (sock < 0) + pg_fatal("sock did not exist: %s", PQcancelErrorMessage(cancelConn)); + + tv.tv_sec = 3; + tv.tv_usec = 0; + + while (true) + { + if (select(sock + 1, &input_mask, &output_mask, NULL, &tv) < 0) + { + if (errno == EINTR) + continue; + pg_fatal("select() failed: %m"); + } + break; + } + } + if (PQcancelStatus(cancelConn) != CONNECTION_OK) + pg_fatal("unexpected cancel connection status: %s", PQcancelErrorMessage(cancelConn)); + confirm_query_canceled(conn); + + PQcancelFinish(cancelConn); + fprintf(stderr, "ok\n"); } diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index a3052a181d1..aa7a25b8f8c 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -1763,6 +1763,7 @@ PG_Locale_Strategy PG_Lock_Status PG_init_t PGcancel +PGcancelConn PGcmdQueueEntry PGconn PGdataValue