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Diffstat (limited to 'fluent-bit/lib/librdkafka-2.1.0/examples/transactions.c')
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1 files changed, 665 insertions, 0 deletions
diff --git a/fluent-bit/lib/librdkafka-2.1.0/examples/transactions.c b/fluent-bit/lib/librdkafka-2.1.0/examples/transactions.c new file mode 100644 index 000000000..0a8b9a8cf --- /dev/null +++ b/fluent-bit/lib/librdkafka-2.1.0/examples/transactions.c @@ -0,0 +1,665 @@ +/* + * librdkafka - Apache Kafka C library + * + * Copyright (c) 2020, Magnus Edenhill + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * 1. Redistributions of source code must retain the above copyright notice, + * this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ + +/** + * @name Transactions example for Apache Kafka 2.5.0 (KIP-447) and later. + * + * This example show-cases a simple transactional consume-process-produce + * application that reads messages from an input topic, extracts all + * numbers from the message's value string, adds them up, and sends + * the sum to the output topic as part of a transaction. + * The transaction is committed every 5 seconds or 100 messages, whichever + * comes first. As the transaction is committed a new transaction is started. + * + * This example makes use of incremental rebalancing (KIP-429) and the + * cooperative-sticky partition.assignment.strategy on the consumer, providing + * hitless rebalances. + */ + +#include <stdio.h> +#include <signal.h> +#include <unistd.h> +#include <string.h> +#include <stdlib.h> +#include <time.h> +#include <ctype.h> + + +/* Typical include path would be <librdkafka/rdkafka.h>, but this program + * is builtin from within the librdkafka source tree and thus differs. */ +#include "rdkafka.h" + + +static volatile sig_atomic_t run = 1; + +/** + * @brief A fatal error has occurred, immediately exit the application. + */ +#define fatal(...) \ + do { \ + fprintf(stderr, "FATAL ERROR: "); \ + fprintf(stderr, __VA_ARGS__); \ + fprintf(stderr, "\n"); \ + exit(1); \ + } while (0) + +/** + * @brief Same as fatal() but takes an rd_kafka_error_t object, prints its + * error message, destroys the object and then exits fatally. + */ +#define fatal_error(what, error) \ + do { \ + fprintf(stderr, "FATAL ERROR: %s: %s: %s\n", what, \ + rd_kafka_error_name(error), \ + rd_kafka_error_string(error)); \ + rd_kafka_error_destroy(error); \ + exit(1); \ + } while (0) + +/** + * @brief Signal termination of program + */ +static void stop(int sig) { + run = 0; +} + + +/** + * @brief Message delivery report callback. + * + * This callback is called exactly once per message, indicating if + * the message was succesfully delivered + * (rkmessage->err == RD_KAFKA_RESP_ERR_NO_ERROR) or permanently + * failed delivery (rkmessage->err != RD_KAFKA_RESP_ERR_NO_ERROR). + * + * The callback is triggered from rd_kafka_poll(), rd_kafka_flush(), + * rd_kafka_abort_transaction() and rd_kafka_commit_transaction() and + * executes on the application's thread. + * + * The current transactional will enter the abortable state if any + * message permanently fails delivery and the application must then + * call rd_kafka_abort_transaction(). But it does not need to be done from + * here, this state is checked by all the transactional APIs and it is better + * to perform this error checking when calling + * rd_kafka_send_offsets_to_transaction() and rd_kafka_commit_transaction(). + * In the case of transactional producing the delivery report callback is + * mostly useful for logging the produce failures. + */ +static void +dr_msg_cb(rd_kafka_t *rk, const rd_kafka_message_t *rkmessage, void *opaque) { + if (rkmessage->err) + fprintf(stderr, "%% Message delivery failed: %s\n", + rd_kafka_err2str(rkmessage->err)); + + /* The rkmessage is destroyed automatically by librdkafka */ +} + + + +/** + * @brief Create a transactional producer. + */ +static rd_kafka_t *create_transactional_producer(const char *brokers, + const char *output_topic) { + rd_kafka_conf_t *conf = rd_kafka_conf_new(); + rd_kafka_t *rk; + char errstr[256]; + rd_kafka_error_t *error; + + if (rd_kafka_conf_set(conf, "bootstrap.servers", brokers, errstr, + sizeof(errstr)) != RD_KAFKA_CONF_OK || + rd_kafka_conf_set(conf, "transactional.id", + "librdkafka_transactions_example", errstr, + sizeof(errstr)) != RD_KAFKA_CONF_OK) + fatal("Failed to configure producer: %s", errstr); + + /* This callback will be called once per message to indicate + * final delivery status. */ + rd_kafka_conf_set_dr_msg_cb(conf, dr_msg_cb); + + /* Create producer */ + rk = rd_kafka_new(RD_KAFKA_PRODUCER, conf, errstr, sizeof(errstr)); + if (!rk) { + rd_kafka_conf_destroy(conf); + fatal("Failed to create producer: %s", errstr); + } + + /* Initialize transactions, this is only performed once + * per transactional producer to acquire its producer id, et.al. */ + error = rd_kafka_init_transactions(rk, -1); + if (error) + fatal_error("init_transactions()", error); + + return rk; +} + + +/** + * @brief Rewind consumer's consume position to the last committed offsets + * for the current assignment. + */ +static void rewind_consumer(rd_kafka_t *consumer) { + rd_kafka_topic_partition_list_t *offsets; + rd_kafka_resp_err_t err; + rd_kafka_error_t *error; + int i; + + /* Get committed offsets for the current assignment, if there + * is a current assignment. */ + err = rd_kafka_assignment(consumer, &offsets); + if (err) { + fprintf(stderr, "No current assignment to rewind: %s\n", + rd_kafka_err2str(err)); + return; + } + + if (offsets->cnt == 0) { + fprintf(stderr, "No current assignment to rewind\n"); + rd_kafka_topic_partition_list_destroy(offsets); + return; + } + + /* Note: Timeout must be lower than max.poll.interval.ms */ + err = rd_kafka_committed(consumer, offsets, 10 * 1000); + if (err) + fatal("Failed to acquire committed offsets: %s", + rd_kafka_err2str(err)); + + /* Seek to committed offset, or start of partition if no + * committed offset is available. */ + for (i = 0; i < offsets->cnt; i++) { + /* No committed offset, start from beginning */ + if (offsets->elems[i].offset < 0) + offsets->elems[i].offset = RD_KAFKA_OFFSET_BEGINNING; + } + + /* Perform seek */ + error = rd_kafka_seek_partitions(consumer, offsets, -1); + if (error) + fatal_error("Failed to seek", error); + + rd_kafka_topic_partition_list_destroy(offsets); +} + +/** + * @brief Abort the current transaction and rewind consumer offsets to + * position where the transaction last started, i.e., the committed + * consumer offset, then begin a new transaction. + */ +static void abort_transaction_and_rewind(rd_kafka_t *consumer, + rd_kafka_t *producer) { + rd_kafka_error_t *error; + + fprintf(stdout, "Aborting transaction and rewinding offsets\n"); + + /* Abort the current transaction */ + error = rd_kafka_abort_transaction(producer, -1); + if (error) + fatal_error("Failed to abort transaction", error); + + /* Rewind consumer */ + rewind_consumer(consumer); + + /* Begin a new transaction */ + error = rd_kafka_begin_transaction(producer); + if (error) + fatal_error("Failed to begin transaction", error); +} + + +/** + * @brief Commit the current transaction. + * + * @returns 1 if transaction was successfully committed, or 0 + * if the current transaction was aborted. + */ +static int commit_transaction(rd_kafka_t *consumer, rd_kafka_t *producer) { + rd_kafka_error_t *error; + rd_kafka_resp_err_t err; + rd_kafka_consumer_group_metadata_t *cgmd; + rd_kafka_topic_partition_list_t *offsets; + + fprintf(stdout, "Committing transaction\n"); + + /* Send the input consumer's offset to transaction + * to commit those offsets along with the transaction itself, + * this is what guarantees exactly-once-semantics (EOS), that + * input (offsets) and output (messages) are committed atomically. */ + + /* Get the consumer's current group metadata state */ + cgmd = rd_kafka_consumer_group_metadata(consumer); + + /* Get consumer's current assignment */ + err = rd_kafka_assignment(consumer, &offsets); + if (err || offsets->cnt == 0) { + /* No partition offsets to commit because consumer + * (most likely) lost the assignment, abort transaction. */ + if (err) + fprintf(stderr, + "Failed to get consumer assignment to commit: " + "%s\n", + rd_kafka_err2str(err)); + else + rd_kafka_topic_partition_list_destroy(offsets); + + error = rd_kafka_abort_transaction(producer, -1); + if (error) + fatal_error("Failed to abort transaction", error); + + return 0; + } + + /* Get consumer's current position for this partition */ + err = rd_kafka_position(consumer, offsets); + if (err) + fatal("Failed to get consumer position: %s", + rd_kafka_err2str(err)); + + /* Send offsets to transaction coordinator */ + error = + rd_kafka_send_offsets_to_transaction(producer, offsets, cgmd, -1); + rd_kafka_consumer_group_metadata_destroy(cgmd); + rd_kafka_topic_partition_list_destroy(offsets); + if (error) { + if (rd_kafka_error_txn_requires_abort(error)) { + fprintf(stderr, + "WARNING: Failed to send offsets to " + "transaction: %s: %s: aborting transaction\n", + rd_kafka_error_name(error), + rd_kafka_error_string(error)); + rd_kafka_error_destroy(error); + + /* Abort transaction */ + error = rd_kafka_abort_transaction(producer, -1); + if (error) + fatal_error("Failed to abort transaction", + error); + return 0; + } else { + fatal_error("Failed to send offsets to transaction", + error); + } + } + + /* Commit the transaction */ + error = rd_kafka_commit_transaction(producer, -1); + if (error) { + if (rd_kafka_error_txn_requires_abort(error)) { + fprintf(stderr, + "WARNING: Failed to commit transaction: " + "%s: %s: aborting transaction\n", + rd_kafka_error_name(error), + rd_kafka_error_string(error)); + rd_kafka_error_destroy(error); + + /* Abort transaction */ + error = rd_kafka_abort_transaction(producer, -1); + if (error) + fatal_error("Failed to abort transaction", + error); + return 0; + } else { + fatal_error("Failed to commit transaction", error); + } + } + + return 1; +} + +/** + * @brief Commit the current transaction and start a new transaction. + */ +static void commit_transaction_and_start_new(rd_kafka_t *consumer, + rd_kafka_t *producer) { + rd_kafka_error_t *error; + + /* Commit transaction. + * If commit failed the transaction is aborted and we need + * to rewind the consumer to the last committed offsets. */ + if (!commit_transaction(consumer, producer)) + rewind_consumer(consumer); + + /* Begin new transaction */ + error = rd_kafka_begin_transaction(producer); + if (error) + fatal_error("Failed to begin new transaction", error); +} + +/** + * @brief The rebalance will be triggered (from rd_kafka_consumer_poll()) + * when the consumer's partition assignment is assigned or revoked. + */ +static void +consumer_group_rebalance_cb(rd_kafka_t *consumer, + rd_kafka_resp_err_t err, + rd_kafka_topic_partition_list_t *partitions, + void *opaque) { + rd_kafka_t *producer = (rd_kafka_t *)opaque; + rd_kafka_error_t *error; + + switch (err) { + case RD_KAFKA_RESP_ERR__ASSIGN_PARTITIONS: + fprintf(stdout, + "Consumer group rebalanced: " + "%d new partition(s) assigned\n", + partitions->cnt); + + /* Start fetching messages for the assigned partitions + * and add them to the consumer's local assignment. */ + error = rd_kafka_incremental_assign(consumer, partitions); + if (error) + fatal_error("Incremental assign failed", error); + break; + + case RD_KAFKA_RESP_ERR__REVOKE_PARTITIONS: + if (rd_kafka_assignment_lost(consumer)) { + fprintf(stdout, + "Consumer group rebalanced: assignment lost: " + "aborting current transaction\n"); + + error = rd_kafka_abort_transaction(producer, -1); + if (error) + fatal_error("Failed to abort transaction", + error); + } else { + fprintf(stdout, + "Consumer group rebalanced: %d partition(s) " + "revoked: committing current transaction\n", + partitions->cnt); + + commit_transaction(consumer, producer); + } + + /* Begin new transaction */ + error = rd_kafka_begin_transaction(producer); + if (error) + fatal_error("Failed to begin transaction", error); + + /* Stop fetching messages for the revoekd partitions + * and remove them from the consumer's local assignment. */ + error = rd_kafka_incremental_unassign(consumer, partitions); + if (error) + fatal_error("Incremental unassign failed", error); + break; + + default: + /* NOTREACHED */ + fatal("Unexpected rebalance event: %s", rd_kafka_err2name(err)); + } +} + + +/** + * @brief Create the input consumer. + */ +static rd_kafka_t *create_input_consumer(const char *brokers, + const char *input_topic, + rd_kafka_t *producer) { + rd_kafka_conf_t *conf = rd_kafka_conf_new(); + rd_kafka_t *rk; + char errstr[256]; + rd_kafka_resp_err_t err; + rd_kafka_topic_partition_list_t *topics; + + if (rd_kafka_conf_set(conf, "bootstrap.servers", brokers, errstr, + sizeof(errstr)) != RD_KAFKA_CONF_OK || + rd_kafka_conf_set(conf, "group.id", + "librdkafka_transactions_example_group", errstr, + sizeof(errstr)) != RD_KAFKA_CONF_OK || + rd_kafka_conf_set(conf, "partition.assignment.strategy", + "cooperative-sticky", errstr, + sizeof(errstr)) != RD_KAFKA_CONF_OK || + rd_kafka_conf_set(conf, "auto.offset.reset", "earliest", errstr, + sizeof(errstr)) != RD_KAFKA_CONF_OK || + /* The input consumer's offsets are explicitly committed with the + * output producer's transaction using + * rd_kafka_send_offsets_to_transaction(), so auto commits + * must be disabled. */ + rd_kafka_conf_set(conf, "enable.auto.commit", "false", errstr, + sizeof(errstr)) != RD_KAFKA_CONF_OK) { + fatal("Failed to configure consumer: %s", errstr); + } + + /* This callback will be called when the consumer group is rebalanced + * and the consumer's partition assignment is assigned or revoked. */ + rd_kafka_conf_set_rebalance_cb(conf, consumer_group_rebalance_cb); + + /* The producer handle is needed in the consumer's rebalance callback + * to be able to abort and commit transactions, so we pass the + * producer as the consumer's opaque. */ + rd_kafka_conf_set_opaque(conf, producer); + + /* Create consumer */ + rk = rd_kafka_new(RD_KAFKA_CONSUMER, conf, errstr, sizeof(errstr)); + if (!rk) { + rd_kafka_conf_destroy(conf); + fatal("Failed to create consumer: %s", errstr); + } + + /* Forward all partition messages to the main queue and + * rd_kafka_consumer_poll(). */ + rd_kafka_poll_set_consumer(rk); + + /* Subscribe to the input topic */ + topics = rd_kafka_topic_partition_list_new(1); + rd_kafka_topic_partition_list_add(topics, input_topic, + /* The partition is ignored in + * rd_kafka_subscribe() */ + RD_KAFKA_PARTITION_UA); + err = rd_kafka_subscribe(rk, topics); + rd_kafka_topic_partition_list_destroy(topics); + if (err) { + rd_kafka_destroy(rk); + fatal("Failed to subscribe to %s: %s\n", input_topic, + rd_kafka_err2str(err)); + } + + return rk; +} + + +/** + * @brief Find and parse next integer string in \p start. + * @returns Pointer after found integer string, or NULL if not found. + */ +static const void * +find_next_int(const void *start, const void *end, int *intp) { + const char *p; + int collecting = 0; + int num = 0; + + for (p = (const char *)start; p < (const char *)end; p++) { + if (isdigit((int)(*p))) { + collecting = 1; + num = (num * 10) + ((int)*p - ((int)'0')); + } else if (collecting) + break; + } + + if (!collecting) + return NULL; /* No integer string found */ + + *intp = num; + + return p; +} + + +/** + * @brief Process a message from the input consumer by parsing all + * integer strings, adding them, and then producing the sum + * the output topic using the transactional producer for the given + * inut partition. + */ +static void process_message(rd_kafka_t *consumer, + rd_kafka_t *producer, + const char *output_topic, + const rd_kafka_message_t *rkmessage) { + int num; + long unsigned sum = 0; + const void *p, *end; + rd_kafka_resp_err_t err; + char value[64]; + + if (rkmessage->len == 0) + return; /* Ignore empty messages */ + + p = rkmessage->payload; + end = ((const char *)rkmessage->payload) + rkmessage->len; + + /* Find and sum all numbers in the message */ + while ((p = find_next_int(p, end, &num))) + sum += num; + + if (sum == 0) + return; /* No integers in message, ignore it. */ + + snprintf(value, sizeof(value), "%lu", sum); + + /* Emit output message on transactional producer */ + while (1) { + err = rd_kafka_producev( + producer, RD_KAFKA_V_TOPIC(output_topic), + /* Use same key as input message */ + RD_KAFKA_V_KEY(rkmessage->key, rkmessage->key_len), + /* Value is the current sum of this + * transaction. */ + RD_KAFKA_V_VALUE(value, strlen(value)), + /* Copy value since it is allocated on the stack */ + RD_KAFKA_V_MSGFLAGS(RD_KAFKA_MSG_F_COPY), RD_KAFKA_V_END); + + if (!err) + break; + else if (err == RD_KAFKA_RESP_ERR__QUEUE_FULL) { + /* If output queue fills up we need to wait for + * some delivery reports and then retry. */ + rd_kafka_poll(producer, 100); + continue; + } else { + fprintf(stderr, + "WARNING: Failed to produce message to %s: " + "%s: aborting transaction\n", + output_topic, rd_kafka_err2str(err)); + abort_transaction_and_rewind(consumer, producer); + return; + } + } +} + + +int main(int argc, char **argv) { + rd_kafka_t *producer, *consumer; + int msgcnt = 0; + time_t last_commit = 0; + const char *brokers, *input_topic, *output_topic; + rd_kafka_error_t *error; + + /* + * Argument validation + */ + if (argc != 4) { + fprintf(stderr, + "%% Usage: %s <broker> <input-topic> <output-topic>\n", + argv[0]); + return 1; + } + + brokers = argv[1]; + input_topic = argv[2]; + output_topic = argv[3]; + + /* Signal handler for clean shutdown */ + signal(SIGINT, stop); + + producer = create_transactional_producer(brokers, output_topic); + + consumer = create_input_consumer(brokers, input_topic, producer); + + fprintf(stdout, + "Expecting integers to sum on input topic %s ...\n" + "To generate input messages you can use:\n" + " $ seq 1 100 | examples/producer %s %s\n" + "Observe summed integers on output topic %s:\n" + " $ examples/consumer %s just-watching %s\n" + "\n", + input_topic, brokers, input_topic, output_topic, brokers, + output_topic); + + /* Begin transaction and start waiting for messages */ + error = rd_kafka_begin_transaction(producer); + if (error) + fatal_error("Failed to begin transaction", error); + + while (run) { + rd_kafka_message_t *msg; + + /* Commit transaction every 100 messages or 5 seconds */ + if (msgcnt > 0 && + (msgcnt > 100 || last_commit + 5 <= time(NULL))) { + printf("msgcnt %d, elapsed %d\n", msgcnt, + (int)(time(NULL) - last_commit)); + commit_transaction_and_start_new(consumer, producer); + msgcnt = 0; + last_commit = time(NULL); + } + + /* Wait for new mesages or error events */ + msg = rd_kafka_consumer_poll(consumer, 1000 /*1 second*/); + if (!msg) + continue; /* Poll timeout */ + + if (msg->err) { + /* Client errors are typically just informational + * since the client will automatically try to recover + * from all types of errors. + * It is thus sufficient for the application to log and + * continue operating when a consumer error is + * encountered. */ + fprintf(stderr, "WARNING: Consumer error: %s\n", + rd_kafka_message_errstr(msg)); + rd_kafka_message_destroy(msg); + continue; + } + + /* Process message */ + process_message(consumer, producer, output_topic, msg); + + rd_kafka_message_destroy(msg); + + msgcnt++; + } + + fprintf(stdout, "Closing consumer\n"); + rd_kafka_consumer_close(consumer); + rd_kafka_destroy(consumer); + + fprintf(stdout, "Closing producer\n"); + rd_kafka_destroy(producer); + + return 0; +} |